SIST-TP ISO/TR 17276:2017
Cosmetics - Analytical approach for screening and quantification methods for heavy metals in cosmetics
Cosmetics - Analytical approach for screening and quantification methods for heavy metals in cosmetics
This Technical Report introduces most common and typical analytical approaches for screening and
quantification of heavy metals of general interest at both raw material and finished product level. This
Technical Report covers techniques from traditional colourimetric reaction, which can be executed
without expensive instrument to the high-end one, like that of inductively coupled plasma-mass
spectrometry (ICP-MS), which allows detection of elements at μg/kg level. Thus, this Technical Report
covers the advantages and disadvantages of each analytical technique so that a suitable approach can
be chosen.
The intent of this Technical Report is not to set or suggest acceptable concentration limits of heavy
metals in both raw materials and finished products which have to be determined by each regulatory
authority.
NOTE 1 The term “heavy metals” is widely used without single definition.
NOTE 2 Elements can be specified as heavy metals by one legislation, while not by others.
Cosmétiques - Approche analytique des méthodes de détection et de quantification des métaux lourds dans les cosmétiques
L'ISO/TR 17276:2014 pr�sente les approches analytiques les plus courantes et les plus classiques pour d�tecter et quantifier les m�taux lourds d'int�r�t g�n�ral � la fois dans les mati�res premi�res et les produits finis. Il traite des techniques allant de la r�action colorim�trique classique, qui peut �tre r�alis�e sans utiliser d'appareils couteux, � la m�thode de pointe, comme la spectrom�trie par torche � plasma coupl�e � la spectrom�trie de masse (ICP-MS), qui permet de d�tecter des �l�ments au niveau du μg/kg. Ainsi, l'ISO/TR 17276:2014 d�crit les avantages et les inconv�nients de chaque technique analytique de fa�on � choisir une approche appropri�e.
Kozmetika - Analizni pristop za presejalne in kvantitativne metode za težke kovine v kozmetiki
To tehnično poročilo uvaja najpogostejše in najobičajnejše analizne pristope za presejanje in kvantifikacijo težkih kovin splošnega pomena tako na ravni surovin kot na ravni končnih proizvodov. To tehnično poročilo zajema tehnike iz tradicionalne kolorimetrične reakcije, ki se lahko izvede z različnimi instrumenti (od osnovnih do vrhunskih), kot je masna spektrometrija z induktivno sklopljeno plazmo (ICP-MS), ki omogoča ugotavljanje prisotnosti elementov na ravni μg/kg. To tehnično poročilo tako zajema prednosti in slabosti vsake analizne tehnike, da se lahko izbere ustrezen pristop.
Namen tega tehničnega poročila ni določiti ali predlagati sprejemljive mejne koncentracije težkih kovin v surovinah in končnih proizvodih, ki jih mora opredeliti posamezen regulativni organ.
OPOMBA 1: Izraz »težke kovine« se pogosto uporablja brez enotne opredelitve.
OPOMBA 2: Elementi so lahko kot težke kovine opredeljeni v okviru določene zakonodaje, ne pa tudi v okviru drugih zakonodaj.
General Information
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Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 17276
First edition
2014-05-01
Cosmetics — Analytical approach for
screening and quantification methods
for heavy metals in cosmetics
Cosmétiques — Approche analytique des méthodes pour l’évaluation
et la quantification des métaux lourds dans les cosmétiques
Reference number
ISO/TR 17276:2014(E)
©
ISO 2014
---------------------- Page: 1 ----------------------
ISO/TR 17276:2014(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2014 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TR 17276:2014(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Principles . 1
2.1 Planning . 1
2.2 Selection of a test substance . 2
2.3 Preparation of samples . 2
2.4 Detection tests and methods . 3
[3][8]
Annex A (informative) Colourimetric reaction . 6
Annex B (informative) X-ray fluorescence .10
Annex C (informative) Quantification of elements in samples .11
Bibliography .16
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ISO/TR 17276:2014(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 217, Cosmetics.
iv © ISO 2014 – All rights reserved
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ISO/TR 17276:2014(E)
Introduction
Heavy metals occur naturally in the environment. Some heavy metals are utilized in many industries,
and some in very small amount are essential minerals to life. On the other hand, heavy metals are often
a concern due to their toxicity. Even for essential minerals, they can be a concern when excess amounts
are ingested, or more generally, when the human exposure is too high, independently of the route of
exposure.
Heavy metals are ubiquitous as they are found in nature (rocks, soil, water, amongst other sources). As
such, these heavy metals can be found as impurities in raw materials, and, while not added intentionally
[1][2]
to cosmetics, might be present as traces in finished products.
The term “heavy metals” is widely used without a single definition. Commonly recognized heavy metals
include, but are not limited to: lead, mercury, cadmium, arsenic, and antimony.
While it is acknowledged that heavy metal traces in cosmetic products are unavoidable due to the
ubiquitous nature of these elements, companies have implemented numerous measures to monitor and
control the amount that might be present.
This Technical Report presents the most common and typical analytical methods and tools for the
detection of heavy metals in cosmetic raw materials and finished products.
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TECHNICAL REPORT ISO/TR 17276:2014(E)
Cosmetics — Analytical approach for screening and
quantification methods for heavy metals in cosmetics
1 Scope
This Technical Report introduces most common and typical analytical approaches for screening and
quantification of heavy metals of general interest at both raw material and finished product level. This
Technical Report covers techniques from traditional colourimetric reaction, which can be executed
without expensive instrument to the high-end one, like that of inductively coupled plasma-mass
spectrometry (ICP-MS), which allows detection of elements at μg/kg level. Thus, this Technical Report
covers the advantages and disadvantages of each analytical technique so that a suitable approach can
be chosen.
The intent of this Technical Report is not to set or suggest acceptable concentration limits of heavy
metals in both raw materials and finished products which have to be determined by each regulatory
authority.
NOTE 1 The term “heavy metals” is widely used without single definition.
NOTE 2 Elements can be specified as heavy metals by one legislation, while not by others.
2 Principles
2.1 Planning
First, the approach is divided into screening and quantification of total heavy metals content. Heavy
metals analysis requires not only technical knowledge and experience, but often requires expensive
facilities and vigorous condition of sample preparation, especially when quantification of heavy metals
content is investigated. The screening approach can contribute to identifying whether heavy metals
levels should be determined using more quantitative methods.
An approach to analyse heavy metals in cosmetics products and raw materials consists of sample
preparation method and detection method. Analytical testing conditions should be determined with
appropriate combination of preparation method and detection method with acceptable validation data.
Sample preparation methods:
— leaching;
— digestion.
Detection tests and methods:
[3-8]
— colourimetric reaction;
— x-ray fluorescence (XRF);
— atomic absorption spectrometry (AAS);
— inductively coupled plasma optical emission spectroscopy (ICP-OES), which is also known as
inductively coupled plasma atomic emission spectroscopy (ICP-AES);
— inductively coupled plasma mass spectrometry (ICP-MS).
These approaches basically do not detect a difference between organic and inorganic compounds of an
element. For example, they do not detect difference between metallic mercury and a phenylmercury
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ISO/TR 17276:2014(E)
compound. Also, they do not detect difference by valence state, such as, between chromium (III) and
chromium (VI). If there is a specific interest in them, appropriate approaches should be taken, e.g. ICP-
MS equipped with chromatography.
Typical approach for the screening and quantification on both raw materials and finished products are
introduced in the Annex A, Annex B, and Annex C. Approaches other than introduced in the annexes can
be effective.
2.2 Selection of a test substance
Screening and quantification of heavy metals can be performed on both raw materials and finished
products.
As heavy metals are found in nature, certain raw materials, such as, inorganic materials can naturally
contain heavy metals. Knowing the source and signature of raw materials is an effective approach to
control the levels of heavy metals in finished products. Monitoring at raw material level can avoid the use
of heavy-metal contaminated raw materials and is an effective way to control heavy metal concentration
in finished products.
2.3 Preparation of samples
2.3.1 General
In many elemental analysis techniques, samples are converted into liquid. The preparation of the
samples is related to the nature of the cosmetic matrix. The sample preparation techniques are basically
classified into two: leaching method and digestion method.
2.3.2 Leaching method
Leaching method is a preparation method in order to determine an amount of heavy metals extracted
from a sample under acidic conditions. The principle of the leaching method is modelling the conditions
of a gastrointestinal fluid or sweat to liberate heavy metals that might be present in products. This
allows estimating an amount of heavy metals to which users can be exposed.
2.3.3 Digestion method
Digestion method is a preparation method in order to determine the total amount of heavy metals
present in a sample. When full digestion method is used, it reliably reveals the worst case scenario of
exposure. Also, full digestion of the matrix reduces interferences in the detection, especially in ICP-MS.
Samples are sometimes simply heated to ashes (dry ashing) in order to remove organic matter. Dry
[9][10]
ashing can be carried out with magnesium nitrate as ashing aids. Other ashing aids might be
[8]
applicable such as magnesium sulfate with sulphuric acid. Since cosmetic matrix is complex, insoluble
matter often remains after ashing and further digestion is often conducted.
Samples are digested by heating, usually with a single acid, sometimes with multiple acids (wet digestion),
rarely with alkali (fusion), in open or closed vessels and are fully or almost entirely dissolved. It often
requires vigorous conditions and cautions concerning possible volatilisation for some metals (such as
[8][11]
cadmium, arsenic, or mercury) to obtain acceptable recovery.
Recent trends are for closed vessel digestion with microwave assistance which can reduce losses of
volatile elements and also improve efficiency in routine analysis. Choice of acids is the important factor
to fully digest samples. For cosmetic products, the usage of hydrofluoric acid (HF) can be considered
highly effective in digestion of silica compounds. The treatment with hydrofluoric acid needs a post-
treatment with boric acid in order to mask remaining HF. Nitric acid, hydrochloric acid, sulphuric acid,
and other acids are also selected to digest samples. Each acid, including HF, has their own advantage
and therefore often used by combination to effect full digestion. There are many publications for heavy
metals analysis, including assessments of sample digestion methods. There is a digestion method
recently published with inter-laboratory results for lead, cadmium, and mercury on different finished
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ISO/TR 17276:2014(E)
products containing inorganic materials. This method describes a digestion process using nitric acid
with hydrochloric acid in a closed vessel under high pressure heat to around 200 °C. The method specifies
[12]
the detailed conditions in order to get reproducible results. The study by the authority reports that
analytical results obtained by nitric acid and those by nitric acid with HF, in comparison. Nitric acid
[13]
digestion gave lower results than nitric acid with HF on some cosmetic products. Nevertheless, if
possible, it is recommended to avoid the use of hydrofluoric acid for safety and hygiene reasons, within
the digestion.
2.4 Detection tests and methods
2.4.1 Colourimetric reaction
This technique has been described as detection test, mostly for raw materials, for heavy metals which
form yellow to dark brown-coloured insoluble sulphide under pH 3,0 to 3,5 condition. Elements which
can be detected by this technique are for instance, lead, bismuth, copper, cadmium, antimony, tin, and
[8]
mercury. The insoluble sulphide produced in the reaction shows dark colour in diluted solutions due
to its colloidal dispersion. As the source of sulphide ion, either sodium sulphide or thioacetamide is
normally used. The density of colour is increased in proportion to the concentration of heavy metals.
The quantity of heavy metals is expressed in terms of concentration of lead, in comparison with a
lead reference solution. The advantage of the technique is that it can be performed without expensive
instruments. The colourimetric test is only applicable for sample solutions which are uncoloured and
free from insoluble matter. Recovery should be determined in an accurate and suitable way, especially if
dry-ashing is used to obtain such solutions. This technique cannot detect selenium and chromium. Also,
zinc produces white precipitate which can cause interference. For this reason, it is important to confirm
the reliability of the test by appropriate validation.
When difference in the hue of the developed colour is observed between samples solution and standard
solution, other techniques should be explored.
[3-7]
NOTE Applications of colourimetric tests are found in several compendia for cosmetics and pharmaceuticals
[3] [4]
such as Japanese Standards of Quasi-drug Ingredients (JSQI) and European Pharmacopoeia. Also, the Japanese
[5] [6]
Standards of Cosmetics Ingredients and Japanese Cosmetics Ingredients Codex can still be referred for actual
applications, especially for English description, although they are not active compendia anymore as they have
basically been consolidated to JSQI.
2.4.2 X-ray fluorescence
2.4.2.1 General
When a sample is irradiated with X-rays which have energy above a certain level, core electrons in
atoms are excited, ejected, and then core holes are created. Subsequently, peripheral electrons fall
into the created core holes and the excess energy which corresponds to the energy level difference are
[14]
released as electromagnetic waves in the X-ray region called “X-ray fluorescence” . Since the energy
level difference is unique to each element, the emitted X-ray fluorescence is also termed a characteristic
X-ray. Identification of the element is possible using these X-ray spectra and the elemental concentration
in the sample can be estimated from the X-ray intensity. The advantage of this technique is that it
is non-destructive analysis. Various sample forms such as solid, liquid, or powder are applicable for
the measurement. The measurements are performed easily and quickly without complicated sample
preparation. Complexity would be realized in quantitative or semi-quantitative analysis because this
technique is matrix-dependent, and therefore, correction or appropriate validation would be required.
For certain elements, sufficient sensitivity can not be obtained, particularly with portable equipment.
2.4.2.2 Types of equipment
Equipment can roughly be classified into two according to detection principles, one is the energy-
dispersive type and the other one is wavelength-dispersive type. Each type has particular features,
therefore, their advantages and disadvantages should be considered to select suitable one.
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ISO/TR 17276:2014(E)
2.4.2.2.1 Energy-dispersive type
Its feature is a semiconductor detector. Since the detector itself has energy resolution, the configuration
of the equipment can be simplified in comparison to the wavelength type. For this reason, size of the
equipment is smaller than the wavelength-dispersive type. Disadvantages are lower sensitivity, and
generally resolution is low as well compared to wavelength-dispersive type. The elements to be detected
are generally from sodium to uranium, and sensitivity tends to be lower in lighter elements.
2.4.2.2.2 Wavelength-dispersive type
The advantages are high detection sensitivity and high energy resolution. The disadvantage is large
equipment size. The elements to be detected are generally from beryllium to uranium. The X-ray
fluorescence generated from the sample goes through a solar slit to be a parallel luminous flux. Then
it strikes an analysing crystal to be diffracted so that specific wavelength is picked up by the detector.
Several types of analysing crystals are available. A crystal with appropriate intervals between crystalline
surfaces has to be selected according to the wavelength range to be analysed. As for an X-ray detector,
a proportional counter tube type is generally used for light elements (beryllium to scandium), and a
scintillation counter is generally used in the detection of X-ray fluorescence having a short wavelength
of around 0,2 nm to 0,3 nm or less (titanium to uranium).
[15]
2.4.3 Atomic absorption spectrometry (AAS)
2.4.3.1 General
Electrons of atoms in the atomizer can be promoted to an excited state in nanoseconds by absorbing
a defined quantity of energy radiation of a given wavelength. This amount of energy is specific to a
particular electron transition for each element. In general, each wavelength corresponds to only one
element. The signal without a sample and with a sample in the atomizer is measured using a detector,
and the ratio between the two values (the absorbance) is converted to analyte concentration using Beer-
Lambert law.
The technique requires standards with known analyte content to establish the relation between the
measured absorbance and the analyte concentration and relies therefore on Beer-Lambert law.
The AAS is composed of radiation source, atomization chamber, monochromator, detector, and readout
device. In order to analyse a sample for its atomic constituents, it has to be atomized. The atomizers
most commonly used nowadays are flames and graphite tube atomizers.
AAS is a very common technique with a good sensitivity and a good specificity. Interference can occur
for some elements in the presence of nitric acid with high amounts of iron, aluminium, and silicium.
The main disadvantages are its mono-elemental capability requirement for complete dissolution of the
samples (except the special application of graphite-furnace AAS with solid sample introduction) and the
relatively high cost.
2.4.3.2 Flame AAS
In flame AAS, the sample solution is introduced into a flame of acetylene and an oxidation gas, such as
air or nitric oxide, and the elements can be atomized. Flame AAS shows high sensitivity on the detection
of alkaline metals and alkaline earth metals.
2.4.3.3 Hydride generation AAS (HG-AAS)
This technique is effective for the elements which are reduced to volatile hydrides by sodium
tetrahydroborate (NaBH ). Therefore, the applicable elements are limited, such as arsenic, bismuth,
4
antimony, and selenium. Volatile hydrides are separated from matrices by introduction into an
atomisation chamber. As a result, HG-AAS shows high sensitivity for these elements.
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ISO/TR 17276:2014(E)
2.4.3.4 Graphite furnace AAS (GF-AAS)
In GF-AAS, an either liquid or solid sample is introduced into the graphite tube where it dries through
electrical heating, and the residues are ashed. In order to achieve repeatability, accuracy, and higher
sensitivity, use of platform for graphite tube is recommended. Matrix modifier is used when target
elements are highly volatile in order to minimize the loss of the elements during heating. In a subsequent
heating step at very high temperatures, elements present in the residue are atomized. During this phase,
the attenuation of the lamp radiation by the atomization in the narrow volume of the graphite tube
can be measured. GF-AAS generally shows higher sensitivity than flame-AAS on many elements, while
background correction is required due to the use of high temperature. A background correction often
applied is Zeeman background correction or deuterium background correction.
2.4.3.5 Cold vapour AAS (CV-AAS)
The analysis of mercury sometimes requires specially designed sample preparation techniques due to
its physico-chemical behaviour and requires either a dedicated preparation of the sample or a dedicated
technique. Since mercury does not require high temperature to be atomized, the technique called
cold vapour is often used for the analysis by taking advantage of its property. Mercury is atomized
either by reduction using reducing agents such as stannous chloride or by heating. Heating method
is sometimes followed by amalgamation with gold to selectively introduce mercury to a cell to obtain
higher sensitivity. Instruments specialized for mercury analysis are commercially available by taking
[10][16][17]
advantage of its property.
2.4.4 Inductively coupled plasma (ICP)
2.4.4.1 General
[18-20]
ICP has excellent ability to excite or ionize elements because of its very high temperature plasma.
When the torch of the ICP is turned on, an intense electromagnetic field is created. Argon gas flowing
through the torch is ignited, and then, the plasma is created. The flow of argon to maintain the plasma
is high (~20 l/min), and the temperature of the plasma is approximately 7 000 K or higher. In most
cases, sample solution is introduced into a nebulizer by a peristaltic pump to create a mist. The mist is
introduced directly into the argon plasma, immediately collides with the electrons and charged ions of
the plasma, and elements of sample become ions. Molecules are destroyed into their respective atoms
which lose electrons, and provoke light emission at the characteristic wavelengths of the elements
involved. Detectors are either MS or OES, MS detectors detect ionized atoms on the basis of m/z, OES
[21]
detectors utilizes the light emitted by excited atoms.
2.4.4.2 ICP-OES
If the ICP is equipped with an optical spectrometer (ICP-OES), the intensity of this emission corresponds
to the concentration of the element within the sample. The ICP-OES has good sensitivity, but some
spectral interference should be considered (many emission lines as in the case of iron). Some interference
equation can decrease this phenomenon.
2.4.4.3 ICP-MS
If the ICP is equipped with a mass detector (ICP-MS), the abundance of ions (isotopes) corresponds to the
concentration of the sample. For ICP-MS, the plasma has higher temperature to increase ion production.
Some mass interferences, such as polyatomic or isotopic can occur. Interference equation can be used,
or some modern equipment install collision cell or high resolution analysers to decrease or eliminate
this problem.
The great advantages of the ICP-OES and ICP-MS are the multi-element capability and the linear dynamic
range. Cost and the fact that samples typically should be in solution are the main disadvantages.
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ISO/TR 17276:2014(E)
Annex A
(informative)
[3][8]
Colourimetric reaction
A.1 General
Elements which can be detected by this technique are, lead, bismuth, copper, cadmium, antimony, tin,
and mercury.
The outline of test procedure is as follows.
1) A test solution (TS) is prepared by dissolving a sample in water containing diluted acetic acid to
adjust pH to 3,0 to 3,5. If necessary, use sulphuric acid, nitric acid, or other acids to incinerate and
remove organic interferences in the sample. Heavy metals in the test solution react with added
sodium sulphide to form coloured-insoluble sulphides.
2) A lead reference solution is processed by the same procedure for a sample.
3) The test solution and the lead reference solution are transferred to Nessler tubes separately, and
the colours of the solutions are compared by observing the tubes from up and side against a white
background.
The use of sodium sulphide TS as colour development reagent is found in Japanese Standards of Quasi-
[3]
drug Ingredients. The sodium sulphide TS can be replaced by thioacetamide as adopted by European
[4][8] [7]
Pharmacopoeia 7.0, USP35-NF 30 and other pharmacopeia.
A.2 Solutions and standard solutions
A.2.1 General
Only essential solutions are introduced in this Technical Report. All reagents should be analytical grade.
A.2.2 Standard lead solution (10 mg/l)
A.3 Apparatus
A.3.1 Nessler tube, colourless, glass-stoppered cylinders with 1,0 mm to 1,5 mm thickness, made of
hard glass. The difference of the height of the graduation line of 50 ml from the bottom among cylinders
does not exceed 2 mm.
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ISO/TR 17276:2014(E)
A.4 Preparation of sample and control solution
A.4.1 Calculation of sample amount for testing
Use a quantity, in g, of the sample to be tested as calculated by the formula. Amount of standard lead
solution is often 2,0 ml, but can be changed in order to achieve the required limit and optimize the test
conditions to improve method reliability.
w = 10 × V/L (A.1)
where
w is the weight of the sample, expressed in g;
V is the amount of standard lead solution, expressed in ml;
L is the heavy metals limit interested, expressed in μg/g.
A.4.2 Selection of sample preparation method
Method 1 can be applied to raw materials that dissolve in water and do not produce precipitation when
diluted acetic acid is added to adjust the pH of the solution 3,0 to 3,5. When these requirements were
not met, or recovery was not enough, explore the applicability of Method 2 to Method 4. If none of these
techniques were applicable, other techniques should be employed.
Method 2 can be commonly applied to organic materials. However, it is not applicable to the raw
materials containing reducing metal, such as copper and insoluble metal oxides arising from ashing,
because hydrochloric acid which is employed in this method cannot fully dissolve these materials.
Method 3 is often effective for raw materials that cannot be fully ashed by Method 2. It is designed to
dissolve these residues by aqua regia. Platinum crucible cannot be used in this method.
Method 4 can be applied when enough recovery was not obtained by Method 2. Burning with ethanol to
ash in the presence of magnesium nitrate suppress the evaporation of metals during ignition.
Method 2 to 4 involve open vessel incineration or digestion. Mercury and arsenic can evaporate during
the process. Separate approach might be necessary when these elements are involved.
A.4.3 Method 1
Place the appropriate calculated amount of the sample in a Nessler tube, and dissolve in sufficient water
to make 40 ml. Add 2 ml of diluted acetic acid and water to make 50 ml, and use this solution as the test
solution. Place the appropriate amount of standard lead solution in another Nessler tube, add 2 ml of
diluted acetic acid and water to make 50 ml, and use this solution as the control solution.
A.4.4 Method 2
Place the appropriate calculated amount of the sample in a quartz or porcelain crucible, cover loosely
with a lid, and carbonize by gentle heating. After cooling, add 2 ml of nitric acid and 5 drops of sulphuric
acid, heat carefully until no more white fumes evolve, and
...
SLOVENSKI STANDARD
SIST-TP ISO/TR 17276:2017
01-november-2017
Kozmetika - Analizni pristop za presejalne in kvantitativne metode za težke kovine
v kozmetiki
Cosmetics - Analytical approach for screening and quantification methods for heavy
metals in cosmetics
Cosmétiques - Approche analytique des méthodes de détection et de quantification des
métaux lourds dans les cosmétiques
Ta slovenski standard je istoveten z: ISO/TR 17276:2014
ICS:
71.100.70 .R]PHWLND7RDOHWQL Cosmetics. Toiletries
SULSRPRþNL
SIST-TP ISO/TR 17276:2017 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TP ISO/TR 17276:2017
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SIST-TP ISO/TR 17276:2017
TECHNICAL ISO/TR
REPORT 17276
First edition
2014-05-01
Cosmetics — Analytical approach for
screening and quantification methods
for heavy metals in cosmetics
Cosmétiques — Approche analytique des méthodes pour l’évaluation
et la quantification des métaux lourds dans les cosmétiques
Reference number
ISO/TR 17276:2014(E)
©
ISO 2014
---------------------- Page: 3 ----------------------
SIST-TP ISO/TR 17276:2017
ISO/TR 17276:2014(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2014 – All rights reserved
---------------------- Page: 4 ----------------------
SIST-TP ISO/TR 17276:2017
ISO/TR 17276:2014(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Principles . 1
2.1 Planning . 1
2.2 Selection of a test substance . 2
2.3 Preparation of samples . 2
2.4 Detection tests and methods . 3
[3][8]
Annex A (informative) Colourimetric reaction . 6
Annex B (informative) X-ray fluorescence .10
Annex C (informative) Quantification of elements in samples .11
Bibliography .16
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Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 217, Cosmetics.
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Introduction
Heavy metals occur naturally in the environment. Some heavy metals are utilized in many industries,
and some in very small amount are essential minerals to life. On the other hand, heavy metals are often
a concern due to their toxicity. Even for essential minerals, they can be a concern when excess amounts
are ingested, or more generally, when the human exposure is too high, independently of the route of
exposure.
Heavy metals are ubiquitous as they are found in nature (rocks, soil, water, amongst other sources). As
such, these heavy metals can be found as impurities in raw materials, and, while not added intentionally
[1][2]
to cosmetics, might be present as traces in finished products.
The term “heavy metals” is widely used without a single definition. Commonly recognized heavy metals
include, but are not limited to: lead, mercury, cadmium, arsenic, and antimony.
While it is acknowledged that heavy metal traces in cosmetic products are unavoidable due to the
ubiquitous nature of these elements, companies have implemented numerous measures to monitor and
control the amount that might be present.
This Technical Report presents the most common and typical analytical methods and tools for the
detection of heavy metals in cosmetic raw materials and finished products.
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TECHNICAL REPORT ISO/TR 17276:2014(E)
Cosmetics — Analytical approach for screening and
quantification methods for heavy metals in cosmetics
1 Scope
This Technical Report introduces most common and typical analytical approaches for screening and
quantification of heavy metals of general interest at both raw material and finished product level. This
Technical Report covers techniques from traditional colourimetric reaction, which can be executed
without expensive instrument to the high-end one, like that of inductively coupled plasma-mass
spectrometry (ICP-MS), which allows detection of elements at μg/kg level. Thus, this Technical Report
covers the advantages and disadvantages of each analytical technique so that a suitable approach can
be chosen.
The intent of this Technical Report is not to set or suggest acceptable concentration limits of heavy
metals in both raw materials and finished products which have to be determined by each regulatory
authority.
NOTE 1 The term “heavy metals” is widely used without single definition.
NOTE 2 Elements can be specified as heavy metals by one legislation, while not by others.
2 Principles
2.1 Planning
First, the approach is divided into screening and quantification of total heavy metals content. Heavy
metals analysis requires not only technical knowledge and experience, but often requires expensive
facilities and vigorous condition of sample preparation, especially when quantification of heavy metals
content is investigated. The screening approach can contribute to identifying whether heavy metals
levels should be determined using more quantitative methods.
An approach to analyse heavy metals in cosmetics products and raw materials consists of sample
preparation method and detection method. Analytical testing conditions should be determined with
appropriate combination of preparation method and detection method with acceptable validation data.
Sample preparation methods:
— leaching;
— digestion.
Detection tests and methods:
[3-8]
— colourimetric reaction;
— x-ray fluorescence (XRF);
— atomic absorption spectrometry (AAS);
— inductively coupled plasma optical emission spectroscopy (ICP-OES), which is also known as
inductively coupled plasma atomic emission spectroscopy (ICP-AES);
— inductively coupled plasma mass spectrometry (ICP-MS).
These approaches basically do not detect a difference between organic and inorganic compounds of an
element. For example, they do not detect difference between metallic mercury and a phenylmercury
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compound. Also, they do not detect difference by valence state, such as, between chromium (III) and
chromium (VI). If there is a specific interest in them, appropriate approaches should be taken, e.g. ICP-
MS equipped with chromatography.
Typical approach for the screening and quantification on both raw materials and finished products are
introduced in the Annex A, Annex B, and Annex C. Approaches other than introduced in the annexes can
be effective.
2.2 Selection of a test substance
Screening and quantification of heavy metals can be performed on both raw materials and finished
products.
As heavy metals are found in nature, certain raw materials, such as, inorganic materials can naturally
contain heavy metals. Knowing the source and signature of raw materials is an effective approach to
control the levels of heavy metals in finished products. Monitoring at raw material level can avoid the use
of heavy-metal contaminated raw materials and is an effective way to control heavy metal concentration
in finished products.
2.3 Preparation of samples
2.3.1 General
In many elemental analysis techniques, samples are converted into liquid. The preparation of the
samples is related to the nature of the cosmetic matrix. The sample preparation techniques are basically
classified into two: leaching method and digestion method.
2.3.2 Leaching method
Leaching method is a preparation method in order to determine an amount of heavy metals extracted
from a sample under acidic conditions. The principle of the leaching method is modelling the conditions
of a gastrointestinal fluid or sweat to liberate heavy metals that might be present in products. This
allows estimating an amount of heavy metals to which users can be exposed.
2.3.3 Digestion method
Digestion method is a preparation method in order to determine the total amount of heavy metals
present in a sample. When full digestion method is used, it reliably reveals the worst case scenario of
exposure. Also, full digestion of the matrix reduces interferences in the detection, especially in ICP-MS.
Samples are sometimes simply heated to ashes (dry ashing) in order to remove organic matter. Dry
[9][10]
ashing can be carried out with magnesium nitrate as ashing aids. Other ashing aids might be
[8]
applicable such as magnesium sulfate with sulphuric acid. Since cosmetic matrix is complex, insoluble
matter often remains after ashing and further digestion is often conducted.
Samples are digested by heating, usually with a single acid, sometimes with multiple acids (wet digestion),
rarely with alkali (fusion), in open or closed vessels and are fully or almost entirely dissolved. It often
requires vigorous conditions and cautions concerning possible volatilisation for some metals (such as
[8][11]
cadmium, arsenic, or mercury) to obtain acceptable recovery.
Recent trends are for closed vessel digestion with microwave assistance which can reduce losses of
volatile elements and also improve efficiency in routine analysis. Choice of acids is the important factor
to fully digest samples. For cosmetic products, the usage of hydrofluoric acid (HF) can be considered
highly effective in digestion of silica compounds. The treatment with hydrofluoric acid needs a post-
treatment with boric acid in order to mask remaining HF. Nitric acid, hydrochloric acid, sulphuric acid,
and other acids are also selected to digest samples. Each acid, including HF, has their own advantage
and therefore often used by combination to effect full digestion. There are many publications for heavy
metals analysis, including assessments of sample digestion methods. There is a digestion method
recently published with inter-laboratory results for lead, cadmium, and mercury on different finished
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products containing inorganic materials. This method describes a digestion process using nitric acid
with hydrochloric acid in a closed vessel under high pressure heat to around 200 °C. The method specifies
[12]
the detailed conditions in order to get reproducible results. The study by the authority reports that
analytical results obtained by nitric acid and those by nitric acid with HF, in comparison. Nitric acid
[13]
digestion gave lower results than nitric acid with HF on some cosmetic products. Nevertheless, if
possible, it is recommended to avoid the use of hydrofluoric acid for safety and hygiene reasons, within
the digestion.
2.4 Detection tests and methods
2.4.1 Colourimetric reaction
This technique has been described as detection test, mostly for raw materials, for heavy metals which
form yellow to dark brown-coloured insoluble sulphide under pH 3,0 to 3,5 condition. Elements which
can be detected by this technique are for instance, lead, bismuth, copper, cadmium, antimony, tin, and
[8]
mercury. The insoluble sulphide produced in the reaction shows dark colour in diluted solutions due
to its colloidal dispersion. As the source of sulphide ion, either sodium sulphide or thioacetamide is
normally used. The density of colour is increased in proportion to the concentration of heavy metals.
The quantity of heavy metals is expressed in terms of concentration of lead, in comparison with a
lead reference solution. The advantage of the technique is that it can be performed without expensive
instruments. The colourimetric test is only applicable for sample solutions which are uncoloured and
free from insoluble matter. Recovery should be determined in an accurate and suitable way, especially if
dry-ashing is used to obtain such solutions. This technique cannot detect selenium and chromium. Also,
zinc produces white precipitate which can cause interference. For this reason, it is important to confirm
the reliability of the test by appropriate validation.
When difference in the hue of the developed colour is observed between samples solution and standard
solution, other techniques should be explored.
[3-7]
NOTE Applications of colourimetric tests are found in several compendia for cosmetics and pharmaceuticals
[3] [4]
such as Japanese Standards of Quasi-drug Ingredients (JSQI) and European Pharmacopoeia. Also, the Japanese
[5] [6]
Standards of Cosmetics Ingredients and Japanese Cosmetics Ingredients Codex can still be referred for actual
applications, especially for English description, although they are not active compendia anymore as they have
basically been consolidated to JSQI.
2.4.2 X-ray fluorescence
2.4.2.1 General
When a sample is irradiated with X-rays which have energy above a certain level, core electrons in
atoms are excited, ejected, and then core holes are created. Subsequently, peripheral electrons fall
into the created core holes and the excess energy which corresponds to the energy level difference are
[14]
released as electromagnetic waves in the X-ray region called “X-ray fluorescence” . Since the energy
level difference is unique to each element, the emitted X-ray fluorescence is also termed a characteristic
X-ray. Identification of the element is possible using these X-ray spectra and the elemental concentration
in the sample can be estimated from the X-ray intensity. The advantage of this technique is that it
is non-destructive analysis. Various sample forms such as solid, liquid, or powder are applicable for
the measurement. The measurements are performed easily and quickly without complicated sample
preparation. Complexity would be realized in quantitative or semi-quantitative analysis because this
technique is matrix-dependent, and therefore, correction or appropriate validation would be required.
For certain elements, sufficient sensitivity can not be obtained, particularly with portable equipment.
2.4.2.2 Types of equipment
Equipment can roughly be classified into two according to detection principles, one is the energy-
dispersive type and the other one is wavelength-dispersive type. Each type has particular features,
therefore, their advantages and disadvantages should be considered to select suitable one.
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2.4.2.2.1 Energy-dispersive type
Its feature is a semiconductor detector. Since the detector itself has energy resolution, the configuration
of the equipment can be simplified in comparison to the wavelength type. For this reason, size of the
equipment is smaller than the wavelength-dispersive type. Disadvantages are lower sensitivity, and
generally resolution is low as well compared to wavelength-dispersive type. The elements to be detected
are generally from sodium to uranium, and sensitivity tends to be lower in lighter elements.
2.4.2.2.2 Wavelength-dispersive type
The advantages are high detection sensitivity and high energy resolution. The disadvantage is large
equipment size. The elements to be detected are generally from beryllium to uranium. The X-ray
fluorescence generated from the sample goes through a solar slit to be a parallel luminous flux. Then
it strikes an analysing crystal to be diffracted so that specific wavelength is picked up by the detector.
Several types of analysing crystals are available. A crystal with appropriate intervals between crystalline
surfaces has to be selected according to the wavelength range to be analysed. As for an X-ray detector,
a proportional counter tube type is generally used for light elements (beryllium to scandium), and a
scintillation counter is generally used in the detection of X-ray fluorescence having a short wavelength
of around 0,2 nm to 0,3 nm or less (titanium to uranium).
[15]
2.4.3 Atomic absorption spectrometry (AAS)
2.4.3.1 General
Electrons of atoms in the atomizer can be promoted to an excited state in nanoseconds by absorbing
a defined quantity of energy radiation of a given wavelength. This amount of energy is specific to a
particular electron transition for each element. In general, each wavelength corresponds to only one
element. The signal without a sample and with a sample in the atomizer is measured using a detector,
and the ratio between the two values (the absorbance) is converted to analyte concentration using Beer-
Lambert law.
The technique requires standards with known analyte content to establish the relation between the
measured absorbance and the analyte concentration and relies therefore on Beer-Lambert law.
The AAS is composed of radiation source, atomization chamber, monochromator, detector, and readout
device. In order to analyse a sample for its atomic constituents, it has to be atomized. The atomizers
most commonly used nowadays are flames and graphite tube atomizers.
AAS is a very common technique with a good sensitivity and a good specificity. Interference can occur
for some elements in the presence of nitric acid with high amounts of iron, aluminium, and silicium.
The main disadvantages are its mono-elemental capability requirement for complete dissolution of the
samples (except the special application of graphite-furnace AAS with solid sample introduction) and the
relatively high cost.
2.4.3.2 Flame AAS
In flame AAS, the sample solution is introduced into a flame of acetylene and an oxidation gas, such as
air or nitric oxide, and the elements can be atomized. Flame AAS shows high sensitivity on the detection
of alkaline metals and alkaline earth metals.
2.4.3.3 Hydride generation AAS (HG-AAS)
This technique is effective for the elements which are reduced to volatile hydrides by sodium
tetrahydroborate (NaBH ). Therefore, the applicable elements are limited, such as arsenic, bismuth,
4
antimony, and selenium. Volatile hydrides are separated from matrices by introduction into an
atomisation chamber. As a result, HG-AAS shows high sensitivity for these elements.
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2.4.3.4 Graphite furnace AAS (GF-AAS)
In GF-AAS, an either liquid or solid sample is introduced into the graphite tube where it dries through
electrical heating, and the residues are ashed. In order to achieve repeatability, accuracy, and higher
sensitivity, use of platform for graphite tube is recommended. Matrix modifier is used when target
elements are highly volatile in order to minimize the loss of the elements during heating. In a subsequent
heating step at very high temperatures, elements present in the residue are atomized. During this phase,
the attenuation of the lamp radiation by the atomization in the narrow volume of the graphite tube
can be measured. GF-AAS generally shows higher sensitivity than flame-AAS on many elements, while
background correction is required due to the use of high temperature. A background correction often
applied is Zeeman background correction or deuterium background correction.
2.4.3.5 Cold vapour AAS (CV-AAS)
The analysis of mercury sometimes requires specially designed sample preparation techniques due to
its physico-chemical behaviour and requires either a dedicated preparation of the sample or a dedicated
technique. Since mercury does not require high temperature to be atomized, the technique called
cold vapour is often used for the analysis by taking advantage of its property. Mercury is atomized
either by reduction using reducing agents such as stannous chloride or by heating. Heating method
is sometimes followed by amalgamation with gold to selectively introduce mercury to a cell to obtain
higher sensitivity. Instruments specialized for mercury analysis are commercially available by taking
[10][16][17]
advantage of its property.
2.4.4 Inductively coupled plasma (ICP)
2.4.4.1 General
[18-20]
ICP has excellent ability to excite or ionize elements because of its very high temperature plasma.
When the torch of the ICP is turned on, an intense electromagnetic field is created. Argon gas flowing
through the torch is ignited, and then, the plasma is created. The flow of argon to maintain the plasma
is high (~20 l/min), and the temperature of the plasma is approximately 7 000 K or higher. In most
cases, sample solution is introduced into a nebulizer by a peristaltic pump to create a mist. The mist is
introduced directly into the argon plasma, immediately collides with the electrons and charged ions of
the plasma, and elements of sample become ions. Molecules are destroyed into their respective atoms
which lose electrons, and provoke light emission at the characteristic wavelengths of the elements
involved. Detectors are either MS or OES, MS detectors detect ionized atoms on the basis of m/z, OES
[21]
detectors utilizes the light emitted by excited atoms.
2.4.4.2 ICP-OES
If the ICP is equipped with an optical spectrometer (ICP-OES), the intensity of this emission corresponds
to the concentration of the element within the sample. The ICP-OES has good sensitivity, but some
spectral interference should be considered (many emission lines as in the case of iron). Some interference
equation can decrease this phenomenon.
2.4.4.3 ICP-MS
If the ICP is equipped with a mass detector (ICP-MS), the abundance of ions (isotopes) corresponds to the
concentration of the sample. For ICP-MS, the plasma has higher temperature to increase ion production.
Some mass interferences, such as polyatomic or isotopic can occur. Interference equation can be used,
or some modern equipment install collision cell or high resolution analysers to decrease or eliminate
this problem.
The great advantages of the ICP-OES and ICP-MS are the multi-element capability and the linear dynamic
range. Cost and the fact that samples typically should be in solution are the main disadvantages.
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Annex A
(informative)
[3][8]
Colourimetric reaction
A.1 General
Elements which can be detected by this technique are, lead, bismuth, copper, cadmium, antimony, tin,
and mercury.
The outline of test procedure is as follows.
1) A test solution (TS) is prepared by dissolving a sample in water containing diluted acetic acid to
adjust pH to 3,0 to 3,5. If necessary, use sulphuric acid, nitric acid, or other acids to incinerate and
remove organic interferences in the sample. Heavy metals in the test solution react with added
sodium sulphide to form coloured-insoluble sulphides.
2) A lead reference solution is processed by the same procedure for a sample.
3) The test solution and the lead reference solution are transferred to Nessler tubes separately, and
the colours of the solutions are compared by observing the tubes from up and side against a white
background.
The use of sodium sulphide TS as colour development reagent is found in Japanese Standards of Quasi-
[3]
drug Ingredients. The sodium sulphide TS can be replaced by thioacetamide as adopted by European
[4][8] [7]
Pharmacopoeia 7.0, USP35-NF 30 and other pharmacopeia.
A.2 Solutions and standard solutions
A.2.1 General
Only essential solutions are introduced in this Technical Report. All reagents should be analytical grade.
A.2.2 Standard lead solution (10 mg/l)
A.3 Apparatus
A.3.1 Nessler tube, colourless, glass-stoppered cylinders with 1,0 mm to 1,5 mm thickness, made of
hard glass. The difference of the height of the graduation line of 50 ml from the bottom among cylinders
does not exceed 2 mm.
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A.4 Preparation of sample and control solution
A.4.1 Calculation of sample amount for testing
Use a quantity, in g, of the sample to be tested as calculated by the formula. Amount of standard lead
solution is often 2,0 ml, but can be changed in order to achieve the required limit and optimize the test
conditions to improve method reliability.
w = 10 × V/L (A.1)
where
w is the weight of the sample, expressed in g;
V is the amount of standard lead solution, expressed in ml;
L is the heavy metals limit interested, expressed in μg/g.
A.4.2 Selection of sample preparation method
Method 1 can be applied to raw materials that dissolve in water and do not produce precipitation when
diluted acetic acid is added to adjust the pH of the solution 3,0 to 3,5. When these requirements were
not met, or recovery was not enough, explore the applicability of Method 2 to Method 4. If none of these
techniques were applicable, other techniques should be employed.
Method 2 can be commonly applied to organic materials. However, it is not applicable to the raw
materials containing reducing metal, such as copper and insoluble metal oxides arising from ashing,
because hydrochloric acid which is employed in this method cannot fully dissolve these materials.
Method 3 is often effective for raw materials that cannot be fully as
...
RAPPORT ISO/TR
TECHNIQUE 17276
Première édition
2014-05-01
Cosmétiques — Approche analytique
des méthodes pour l’évaluation et la
quantification des métaux lourds dans
les cosmétiques
Cosmetics — Analytical approach for screening and quantification
methods for heavy metals in cosmetics
Numéro de référence
ISO/TR 17276:2014(F)
©
ISO 2014
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ISO/TR 17276:2014(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2014
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni utilisée
sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie, l’affichage sur
l’internet ou sur un Intranet, sans autorisation écrite préalable. Les demandes d’autorisation peuvent être adressées à l’ISO à
l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Publié en Suisse
ii © ISO 2014 – Tous droits réservés
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ISO/TR 17276:2014(F)
Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d’application . 1
2 Principes . 1
2.1 Planification . 1
2.2 Sélection d’une substance d’essai . 2
2.3 Préparation des échantillons . 2
2.4 Essais et méthodes de détection . 3
[3][8]
Annexe A (informative) Réaction colorimétrique . 7
Annexe B (informative) Fluorescence X .11
Annexe C (informative) Quantification des éléments présents dans les échantillons .12
Bibliographie .18
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ISO/TR 17276:2014(F)
Avant-propos
L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes
nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est
en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.
L’ISO collabore étroitement avec la Commission électrotechnique internationale (CEI) en ce qui concerne
la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/CEI, Partie 1. Il convient, en particulier de prendre note des différents
critères d’approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/CEI, Partie 2 (voir www.
iso.org/directives).
L’attention est appelée sur le fait que certains des éléments du présent document peuvent faire l’objet de
droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant les
références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de l’élaboration
du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de brevets reçues par
l’ISO (voir www.iso.org/brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la signification des termes et expressions spécifiques de l’ISO liés à l’évaluation de
la conformité, ou pour toute information au sujet de l’adhésion de l’ISO aux principes de l’OMC concernant
les obstacles techniques au commerce (OTC), voir le lien suivant: Avant-propos — Informations
supplémentaires.
Le comité chargé de l’élaboration du présent document est l’ISO/TC 217, Cosmétiques, GT 3, Méthodes
analytiques.
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ISO/TR 17276:2014(F)
Introduction
Les métaux lourds sont naturellement présents dans l’environnement. Certains métaux lourds sont
utilisés dans de nombreux secteurs industriels, et d’autres, présents en très faibles quantités, sont des
minéraux essentiels à la vie. Par ailleurs, les métaux lourds représentent souvent un problème en raison
de leur toxicité. Même pour les minéraux essentiels, ils peuvent représenter un problème lorsque des
quantités excessives sont ingérées, ou plus généralement, lorsque l’exposition humaine est trop élevée,
quelle que soit la voie d’exposition.
Les métaux lourds sont partout dans la nature (notamment dans les rochers, le sol, l’eau). ces métaux
lourds peuvent ainsi être présents sous forme d’impuretés dans les matières premières et peuvent
également se retrouver à l’état de traces dans les produits finis, sans toutefois avoir été ajoutés
[1][2]
intentionnellement aux cosmétiques.
Le terme «métaux lourds» est couramment utilisé sans définition unique. Les métaux lourds les plus
connus sont, entre autres: le plomb, le mercure, le cadmium, l’arsenic et l’antimoine.
Même s’il est admis que les traces de métaux lourds dans les produits cosmétiques sont inévitables en
raison de l’omniprésence de ces éléments, les entreprises ont mis en place de nombreuses mesures pour
surveiller et contrôler la quantité susceptible d’être présente.
Le présent Rapport technique présente les méthodes et outils analytiques les plus courants et les
plus classiques pour la détection des métaux lourds dans les matières premières et les produits finis
cosmétiques.
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RAPPORT TECHNIQUE ISO/TR 17276:2014(F)
Cosmétiques — Approche analytique des méthodes pour
l’évaluation et la quantification des métaux lourds dans les
cosmétiques
1 Domaine d’application
Le présent Rapport technique présente les approches analytiques les plus courantes et les plus classiques
pour détecter et quantifier les métaux lourds d’intérêt général à la fois dans les matières premières et
les produits finis. Il traite des techniques allant de la réaction colorimétrique classique, qui peut être
réalisée sans utiliser d’appareils couteux, à la méthode de pointe, comme la spectrométrie par torche à
plasma couplée à la spectrométrie de masse (ICP-MS), qui permet de détecter des éléments au niveau du
μg/kg. Ainsi, le présent Rapport technique décrit les avantages et les inconvénients de chaque technique
analytique de façon à choisir une approche appropriée.
L’objectif du présent Rapport technique n’est pas de définir ou de suggérer les limites de concentrations
acceptables de métaux lourds dans les matières premières et les produits finis qui sont à déterminer par
chaque autorité réglementaire.
NOTE 1 Le terme «métaux lourds» est couramment utilisé sans définition unique.
NOTE 2 Les éléments peuvent être définis comme étant des métaux lourds par une législation mais pas par
d’autres.
2 Principes
2.1 Planification
Tout d’abord, l’approche comprend deux étapes: la détection et la quantification de la teneur totale en
métaux lourds. L’analyse des métaux lourds requiert non seulement des connaissances techniques et
de l’expérience, mais elle nécessite également des installations couteuses et des conditions rigoureuses
de préparation des échantillons, notamment lors de la quantification de la teneur en métaux lourds.
L’approche de détection peut contribuer à identifier s’il convient de déterminer les teneurs en métaux
lourds en utilisant des méthodes plus quantitatives.
L’approche consistant à analyser les métaux lourds dans les produits cosmétiques et les matières
premières comprend une méthode de préparation des échantillons et une méthode de détection. Il
convient de déterminer les conditions des essais analytiques en combinant de manière adéquate la
méthode de préparation et la méthode de détection avec des données de validation acceptables.
Méthodes de préparation des échantillons:
— lixiviation;
— minéralisation.
Essais et méthodes de détection:
[3][4][5][6][7][8]
— réaction colorimétrique;
— fluorescence X (XRF);
— spectrométrie d’absorption atomique (AAS);
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— spectroscopie par torche à plasma couplée à la spectrométrie d’émission optique (ICP-OES),
également connue sous le nom de spectroscopie par torche à plasma couplée à la spectroscopie
d’émission atomique (ICP-AES);
— spectroscopie par torche à plasma couplée à la spectrométrie de masse (ICP-MS).
En principe, ces approches ne détectent aucune différence entre les composés organiques et inorganiques
d’un élément. Par exemple, elles ne détectent pas de différences entre le mercure métallique et le composé
du phénylmercure. Elles ne détectent pas non plus de différences en fonction des valences, par exemple
entre le chrome (III) et le chrome (IV). En cas d’intérêt spécifique pour l’un d’entre eux, il convient de
choisir des approches adéquates, par exemple l’ICP-MS couplée à la chromatographie.
Les approches courantes de détection et de quantification (sur matières premières et produits finis)
sont présentées aux Annexes A, B et C. D’autres approches que celles données dans les annexes peuvent
être efficaces.
2.2 Sélection d’une substance d’essai
La détection et la quantification des métaux lourds peuvent être effectuées sur les matières premières
et les produits finis.
Les métaux lourds étant présents dans la nature, certaines matières premières, telles que les
matières inorganiques, peuvent naturellement contenir des métaux lourds. Connaître l’origine et les
caractéristiques des matières premières permet de contrôler efficacement les teneurs en métaux lourds
dans les produits finis. La surveillance au niveau des matières premières peut éviter l’utilisation de
matières premières contaminées par des métaux lourds et permet de contrôler efficacement les teneurs
en métaux lourds dans les produits finis.
2.3 Préparation des échantillons
2.3.1 Généralités
Dans de nombreuses techniques analytiques élémentaires, les échantillons sont convertis en liquides.
La préparation des échantillons dépend de la nature de la matrice cosmétique. Les techniques de
préparation des échantillons sont en principe classées en deux catégories: méthode de lixiviation et
méthode de minéralisation.
2.3.2 Méthode de lixiviation
La méthode de lixiviation est une méthode de préparation servant à déterminer la quantité de métaux
lourds extraite d’un échantillon dans des conditions acides. La méthode de lixiviation consiste à
reproduire les conditions d’un liquide gastro-intestinal ou d’une sudation de façon à libérer les métaux
lourds susceptibles d’être présents dans les produits. Ceci permet d’estimer la quantité de métaux lourds
à laquelle les utilisateurs peuvent être exposés.
2.3.3 Méthode de minéralisation
La méthode de minéralisation est une méthode de préparation visant à déterminer la quantité totale de
métaux lourds présents dans un échantillon. Lorsque la méthode de minéralisation complète est utilise,
elle révèle avec fiabilité le pire scénario d’exposition. De plus, la minéralisation complète de la matrice
réduit les interférences lors de la détection, notamment l’ICP-MS.
Les échantillons sont parfois simplement chauffés jusqu’à l’obtention de cendres (calcination) pour
éliminer la matière organique. La calcination peut être effectuée en utilisant du nitrate de magnésium
[9][10]
comme adjuvant de calcination. D’autres adjuvants de calcination peuvent être utilisés, par exemple
[8]
du sulfate de magnésium avec de l’acide sulfurique. La matrice cosmétique étant complexe, la matière
insoluble reste souvent présente après la calcination et une nouvelle minéralisation est fréquemment
réalisée.
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Les échantillons sont minéralisés en les chauffant, généralement avec un seul acide, parfois avec plusieurs
acides (minéralisation par voie humide), rarement avec des alcalis (fusion), dans des récipients ouverts
ou fermés, et sont complètement ou presque complètement dissous. Il est souvent nécessaire d’appliquer
des conditions rigoureuses et d’être vigilant en ce qui concerne la possibilité de volatilisation de
certains métaux (notamment le cadmium, l’arsenic ou le mercure) pour obtenir un taux de récupération
[8][11]
acceptable.
Les dernières tendances sont à la minéralisation en récipient fermé avec assistance par micro-ondes,
qui peut réduire les pertes d’éléments volatils et également améliorer l’efficacité de l’analyse de routine.
Le choix des acides est un facteur important pour la minéralisation complète des échantillons. Pour les
produits cosmétiques, l’utilisation d’acide fluorhydrique (HF) peut être considérée comme très efficace
dans la minéralisation des composés de silice. Le traitement à l’acide fluorhydrique nécessite un post-
traitement à l’acide borique pour masquer le HF restant. L’acide nitrique, l’acide chlorhydrique, l’acide
sulfurique et d’autres acides sont également choisis pour minéraliser les échantillons. Chaque acide,
y compris le HF, a ses propres avantages. Les acides sont donc souvent utilisés de manière combinée
pour effectuer une minéralisation complète. Il existe de nombreuses publications concernant l’analyse
des métaux lourds, notamment les évaluations des méthodes de minéralisation des échantillons. Une
méthode de minéralisation a récemment fait l’objet d’une publication accompagnée des résultats pour
le plomb, le cadmium et le mercure sur différents produits finis contenant des matières inorganiques.
Cette méthode décrit un processus de minéralisation utilisant de l’acide nitrique avec de l’acide
chlorhydrique dans un récipient fermé sous haute pression à une chaleur d’environ 200 °C. La méthode
[12]
spécifie les conditions détaillées pour obtenir des résultats reproductibles. L’étude réalisée par une
autorité donne une comparaison des résultats analytiques obtenus avec l’acide nitrique et ceux obtenus
avec l’acide nitrique et le HF. La minéralisation avec l’acide nitrique a permis d’obtenir de moins bons
[13]
résultats qu’avec l’acide nitrique et le HF sur des produits cosmétiques identiques. Toutefois, si cela
est possible, il est recommandé d’éviter l’utilisation d’acide fluorhydrique pour des raisons de sécurité
et d’hygiène, lors de la minéralisation.
2.4 Essais et méthodes de détection
2.4.1 Réaction colorimétrique
Cette technique a été décrite en tant qu’essai de détection de métaux lourds, principalement pour les
matières premières, qui forment du sulfure insoluble de couleur jaune à marron foncé lorsque le pH
se situe entre 3,0 et 3,5. Les éléments qui peuvent être détectés à l’aide de cette technique sont, par
[8]
exemple, le plomb, le bismuth, le cuivre, le cadmium, l’antimoine, l’étain et le mercure. En raison de
sa dispersion colloïdale, le sulfure insoluble produit lors de la réaction présente une couleur sombre
dans les solutions diluées. En tant que source d’ion sulfure, le sulfure de sodium ou le thioacétamide
est normalement utilisé. L’intensité de la couleur augmente proportionnellement à la concentration
en métaux lourds. La quantité de métaux lourds est exprimée en termes de concentration en plomb,
comparée à une solution de référence à base de plomb. L’avantage de cette technique est qu’elle peut être
appliquée sans utiliser d’appareils couteux. L’essai colorimétrique est uniquement applicable pour les
solutions d’échantillons non colorées et exemptes de matière insoluble. Il convient de déterminer le taux
de récupération de manière précise et appropriée, notamment si la calcination est utilisée pour obtenir
ces solutions. Cette technique ne permet pas de détecter le sélénium et le chrome. De plus, le zinc produit
un précipité blanc qui peut provoquer des interférences. Pour cette raison, il est important de confirmer
la fiabilité de l’essai en réalisant une validation appropriée.
Si une différence de tonalité chromatique de la couleur développée est observée entre la solution
d’échantillons et la solution étalon, il convient d’envisager d’autres techniques.
NOTE Des applications d’essais colorimétriques sont présentes dans plusieurs compendiums des produits
[3][4][5][6][7][8]
cosmétiques et pharmaceutiques tels que les normes japonaises sur les quasi-médicaments (JSQI)
[3] [4] [5]
et la Pharmacopée européenne. De plus, les normes japonaises sur les ingrédients cosmétiques et le
[6]
Codex japonais des ingrédients cosmétiques peuvent toujours être consultés pour les applications pratiques,
notamment la description en anglais, même s’ils ne constituent plus des compendiums actifs du fait de leur
consolidation selon les JSQI.
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2.4.2 Fluorescence X
2.4.2.1 Généralités
Lorsqu’un échantillon est irradié avec des rayons X ayant une énergie supérieure à un certain niveau,
les électrons de cœur dans les atomes sont excités et éjectés, puis des lacunes électroniques sont créés.
Les électrons périphériques viennent ensuite combler les lacunes créées et l’excédent d’énergie qui
correspond à la différence de niveau d’énergie est libéré sous forme d’ondes électromagnétiques dans le
[14]
domaine des rayons X appelé «fluorescence X» . Étant donné que la différence de niveau d’énergie est
propre à chaque élément, la fluorescence X émise est également appelée «rayonnement X caractéristique».
L’identification de l’élément peut être réalisée en utilisant ces spectres de rayons X et la concentration
élémentaire dans l’échantillon peut être estimée d’après l’intensité des rayons X. L’avantage de cette
technique est qu’elle permet une analyse non destructive. Plusieurs formes d’échantillons, notamment
solides, liquides ou en poudre, sont applicables pour le mesurage. Les mesurages sont effectués
facilement et rapidement sans préparation d’échantillons complexe. Des éléments de complexité peuvent
apparaître en cas d’analyse quantitative ou semi-quantitative car cette technique dépend de la matrice,
une correction ou une validation appropriée s’avérant alors nécessaire. Pour certains éléments, une
sensibilité suffisante ne peut pas être obtenue, en particulier avec un équipement portatif.
2.4.2.2 Types d’équipement
L’équipement peut être classé en deux catégories selon les principes de détection: l’un est à dispersion
d’énergie et l’autre à dispersion de longueur d’onde. Chaque type ayant ses propres caractéristiques, il
convient donc d’examiner leurs avantages et inconvénients de façon à choisir le plus adapté.
2.4.2.2.1 Équipement à dispersion d’énergie
Il possède les caractéristiques d’un détecteur à semi-conducteur. Le détecteur ayant sa propre résolution
en énergie, la configuration de l’équipement peut être simplifiée par rapport à l’équipement à dispersion
de longueur d’onde. Pour cette raison, cet équipement est plus petit que celui à dispersion de longueur
d’onde. Les inconvénients sont une moins bonne sensibilité et, en général, une résolution plus faible que
celle de l’équipement à dispersion de longueur d’onde. Les éléments détectables vont généralement du
sodium à l’uranium, et la sensibilité a tendance à être moins élevée pour les éléments plus légers.
2.4.2.2.2 Équipement à dispersion de longueur d’onde
Les avantages sont une sensibilité de détection élevée et une haute résolution en énergie. L’inconvénient
tient aux grandes dimensions de l’équipement. Les éléments à détecter vont généralement du béryllium à
l’uranium. La fluorescence X générée par l’échantillon traverse une fente pour produire un flux lumineux
parallèle. Après incidence d’un cristal analyseur elle est diffractée de manière à ce qu’une longueur
d’onde spécifique soit captée par le détecteur.
Il existe plusieurs types de cristaux analyseurs. Un cristal ayant des intervalles appropriés entre les
surfaces cristallines doit être choisi en fonction du domaine de longueur d’onde à analyser. En ce qui
concerne un détecteur de rayons X, un tube compteur proportionnel est généralement utilisé pour les
éléments légers (du béryllium au scandium) et un compteur à scintillation est généralement utilisé pour
détecter une fluorescence X de courte longueur d’onde d’environ 0,2 nm à 0,3 nm ou moins (du titane à
l’uranium).
[15]
2.4.3 Spectrométrie d’absorption atomique (AAS)
2.4.3.1 Généralités
Les électrons des atomes présents dans la source d’atomisation peuvent passer à un état excité en
quelques nanosecondes en absorbant une quantité définie d’énergie de rayonnement d’une longueur
d’onde donnée. Cette quantité d’énergie est propre à chaque transition électronique pour chaque
élément. En général, chaque longueur d’onde correspond à un seul élément. Le signal sans échantillon
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et avec échantillon dans la source d’atomisation est mesuré à l’aide d’un détecteur, et le rapport entre
les deux valeurs (l’absorbance) est converti en concentration d’analyte d’après la loi de Beer-Lambert.
Cette technique nécessite des étalons ayant une teneur en analyte connue pour établir la relation entre
l’absorbance mesurée et la concentration d’analyte. Elle repose donc sur la loi de Beer-Lambert.
L’AAS se compose d’une source de rayonnement, d’une chambre d’atomisation, d’un monochromateur,
d’un détecteur et d’un dispositif indicateur. Pour analyser les constituants atomiques d’un échantillon,
il doit être atomisé. Les atomiseurs les plus utilisés de nos jours sont les atomiseurs de flamme et à tube
de graphite.
L’AAS est une technique très courante qui présente une bonne sensibilité et une bonne spécificité. Des
interférences peuvent apparaître pour certains éléments en présence d’acide nitrique avec de grandes
quantités de fer, d’aluminium et de silicium. Les principaux inconvénients sont la nécessité d’une
dissolution complète des échantillons pour une application mono-élément (hormis l’application spéciale
de l’AAS à four graphite avec introduction d’échantillon solide) et son coût relativement élevé.
2.4.3.2 AAS à flamme
Lors de l’AAS à flamme, la solution d’échantillon est introduite dans une flamme d’acétylène et un gaz
oxydant tel que l’air ou l’oxyde nitrique, et les éléments peuvent être atomisés. L’AAS à flamme possède
une haute sensibilité de détection des métaux alcalins et des métaux alcalino-terreux.
2.4.3.3 AAS à génération d’hydrure (HG-AAS)
Cette technique est efficace pour les éléments qui sont réduits en hydrures volatils par du tétrahydroborate
de sodium (NaBH ). Par conséquent, les éléments concernés sont limités, par exemple l’arsenic, le
4
bismuth, l’antimoine et le sélénium. Les hydrures volatils sont séparés des matrices en les introduisant
dans une chambre d’atomisation. La HG-AAS présente donc une haute sensibilité pour ces éléments.
2.4.3.4 AAS à four graphite (GF-AAS)
Lors d’une GF-AAS, un échantillon liquide ou solide est introduit dans le tube de graphite où il est séché
par chauffage électrique, et les résidus sont calcinés. Pour obtenir une répétabilité, une exactitude et une
meilleure sensibilité, il est recommandé d’utiliser la plate-forme pour tube de graphite. Le modificateur
de matrice est utilisé lorsque les éléments cibles sont hautement volatils, afin de réduire au maximum
la perte des éléments pendant le chauffage. Lors d’une étape de chauffage ultérieure à très haute
température, les éléments présents dans le résidu sont atomisés. Pendant cette phase, l’atténuation du
rayonnement de la lampe par l’atomisation dans le volume étroit du tube de graphite peut être mesurée.
La GF-AAS présente généralement une meilleure sensibilité que l’AAS par flamme pour de nombreux
éléments, même si une correction de fond est requise en raison de l’utilisation d’une haute température.
Une correction de fond souvent appliquée est la correction de fond Zeeman ou la correction de fond au
deutérium.
2.4.3.5 AAS à vapeur froide (CV-AAS)
L’analyse du mercure requiert parfois des techniques spécifiques de préparation de l’échantillon en
raison de son comportement physicochimique et nécessite une préparation spéciale de l’échantillon
ou une technique dédiée. Étant donné que le mercure ne requiert pas de températures élevées pour
être atomisé, la technique dite de la vapeur froide est souvent utilisée pour l’analyse et exploite cette
propriété. Le mercure est atomisé soit par réduction à l’aide de réducteurs tels que le chlorure stanneux
soit par chauffage. La méthode de chauffage est souvent suivie d’une amalgamation avec de l’or pour
introduire de façon sélective du mercure dans une cellule afin d’obtenir une meilleure sensibilité. Les
[10]
appareils dédiés à l’analyse du mercure et disponibles dans le commerce exploitent cette propriété.
[16][17]
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2.4.4 Plasma à couplage inductif (ICP)
2.4.4.1 Généralités
L’ICP possède une excellente capacité d’excitation ou d’ionisation des éléments grâce à son plasma à très
[18][19][20]
haute température. Lorsque la torche de l’ICP est mise en marche, un champ électromagnétique
intense est créé. Le gaz argon qui circule dans la torche s’enflamme et le plasma est créé. Le flux d’argon
nécessaire pour maintenir le plasma est élevé (~20 l/min) et la température du plasma est d’environ
7 000 K ou plus. Dans la majorité des cas, la solution d’échantillon est introduite dans un nébuliseur
par une pompe péristaltique pour créer un brouillard. Le brouillard est directement introduit dans la
plasma d’argon, entre immédiatement en collision avec les électrons et les ions chargés du plasma, et
les éléments de l’échantillon deviennent des ions. Les molécules sont détruites en atomes respectifs qui
perdent des électrons, et provoquent une émission de lumière aux longueurs d’onde caractéristiques des
éléments impliqués. Les détecteurs sont soit des détecteurs MS soit des détecteurs OES, les détecteurs
MS détectant les atomes ionisés sur la base des m/z et les détecteurs OES utilisant la lumière émise par
[21]
les atomes excités.
2.4.4.2 ICP-OES
Si l’ICP est équipé d’un spectromètre optique (ICP-OES), l’intensité de cette émission correspond à la
concentration de l’élément dans l’échantillon. L’ICP-OES possède une bonne sensibilité, mais il convient
de tenir compte de certaines interférences spectrales (nombreuses raies d’émission comme dans le cas
du fer). Des équations d’interférence peuvent atténuer ce phénomène.
2.4.4.3 ICP-MS
Si l’ICP est équipé d’un détecteur de masse (ICP-MS), l’abondance d’ions (isotopes) correspond à la
concentration de l’échantillon. Pour l’ICP-MS, le plasma a une température plus élevée pour accroître la
production d’ions. Des interférences de masse, telles que des interférences polyatomiques ou isotopiques,
peuvent se produire. L’équation d’interférence peut être utilisée, ou certains appareils modernes
équipés de cellules de collision ou d’analyseurs à haute résolution peuvent être employés pour atténuer
ou éliminer ce problème.
Les principaux avantages de l’ICP-OES et de l’ICP-MS sont la fonction multiélément et le domaine de
linéarité. Les principaux inconvénients sont le coût et le fait que les échantillons doivent généralement
être mis en solution.
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ISO/TR 17276:2014(F)
Annexe A
(informative)
...
Questions, Comments and Discussion
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