EN 17851:2023
(Main)Foodstuffs - Determination of elements and their chemical species -Determination of Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U and Zn in foodstuffs by inductively coupled plasma mass spectrometry (ICP-MS) after pressure digestion
Foodstuffs - Determination of elements and their chemical species -Determination of Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U and Zn in foodstuffs by inductively coupled plasma mass spectrometry (ICP-MS) after pressure digestion
This document specifies a method for the determination of Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U and Zn in foodstuffs by ICP-MS after pressure digestion.
The following foodstuffs were analysed for the elements listed in Table 1 in an interlaboratory study: Banana (deep-frozen), Cocoa powder, Wheat noodle powder, Currant nectar (deep-frozen), Milk powder, Oyster (dried), Celery (dried), Dogfish liver (dried), Liver (deep-frozen), Kale (dried).
Table 1 - Rangea
....
Lebensmittel - Bestimmung von Elementen und ihren Verbindungen - Bestimmung von Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U und Zn mit induktiv gekoppelter Plasma-Massenspektrometrie (ICP-MS) nach Druckaufschluss
In diesem Dokument wird ein Verfahren zur Bestimmung von Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U und Zn in Lebensmitteln durch Massenspektrometrie mit induktiv gekoppeltem Plasma (ICP MS) nach Druckaufschluss angegeben.
In einem Ringversuch wurden folgende Lebensmittel auf die in Tabelle 1 aufgeführten Elemente untersucht: Banane (tiefgefroren), Kakaopulver, Weizennudelpulver, Johannisbeernektar (tiefgefroren), Milchpulver, Auster (getrocknet), Sellerie (getrocknet), Katzenhaileber (getrocknet), Leber (tiefgefroren), Grünkohl (getrocknet).
Tabelle 1 - Anwendungsbereich
...
Produits alimentaires - Détermination des éléments et de leurs espèces chimiques - Détermination des éléments Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U et Zn dans les produits alimentaires par spectrométrie de masse avec plasma à couplage inductif (ICP-MS) après digestion sous pression
Le présent document spécifie une méthode de dosage des éléments Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U et Zn dans les produits alimentaires par ICP-MS après digestion sous pression.
Les produits alimentaires suivants ont été analysés par rapport aux éléments répertoriés dans le Tableau 1 lors d’une étude interlaboratoires : banane (surgelée), cacao en poudre, nouille de blé en poudre, nectar de groseille (surgelé), lait en poudre, huître (déshydratée), céleri (déshydraté), foie de saumonette (déshydraté), foie (surgelé), chou vert (déshydraté).
Tableau 1 - Gamme
...
Živila - Določevanje elementov in njihovih kemijskih oblik - Določevanje Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U in Zn v živilih z masno spektrometrijo z induktivno sklopljeno plazmo (ICP-MS) po razklopu pod tlakom
Ta dokument določa metodo za določevanje Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U in Zn v živilih z masno spektrometrijo z induktivno sklopljeno plazmo (ICP-MS) po razklopu pod tlakom.
V medlaboratorijski študiji so bila za elemente, navedene v preglednici 1, analizirana naslednja živila:
banana (globoko zamrznjena), kakav v prahu, pšenični rezanci v prahu, ribezov nektar (globoko zamrznjen), mleko v prahu,
ostriga (posušena), zelena (posušena), ribja jetra (posušena), jetra (globoko zamrznjena), ohrovt (posušen).
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2023
Živila - Določevanje elementov in njihovih kemijskih oblik - Določevanje Ag, As,
Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U in Zn v živilih z masno spektrometrijo z
induktivno sklopljeno plazmo (ICP-MS) po razklopu pod tlakom
Foodstuffs - Determination of elements and their chemical species - Determination of Ag,
As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U and Zn in foodstuffs by inductively coupled
plasma mass spectrometry (ICP-MS) after pressure digestion
Lebensmittel - Bestimmung von Elementen und ihren Verbindungen - Bestimmung von
Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U und Zn mit induktiv gekoppelter
Plasma-Massenspektrometrie (ICP-MS) nach Druckaufschluss
Produits alimentaires - Détermination des éléments et de leurs espèces chimiques -
Détermination des éléments Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U et Zn dans
les produits alimentaires par spectrométrie de masse avec plasma à couplage inductif
(ICP-MS) après digestion sous pression
Ta slovenski standard je istoveten z: EN 17851:2023
ICS:
67.050 Splošne preskusne in General methods of tests and
analizne metode za živilske analysis for food products
proizvode
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 17851
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2023
EUROPÄISCHE NORM
ICS 67.050
English Version
Foodstuffs - Determination of elements and their chemical
species -Determination of Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni,
Pb, Se, Tl, U and Zn in foodstuffs by inductively coupled
plasma mass spectrometry (ICP-MS) after pressure
digestion
Produits alimentaires - Détermination des éléments et Lebensmittel - Bestimmung von Elementen und ihren
de leurs espèces chimiques - Détermination des Verbindungen - Bestimmung von Ag, As, Cd, Co, Cr, Cu,
éléments Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U Mn, Mo, Ni, Pb, Se, Tl, U und Zn mit induktiv
et Zn dans les produits alimentaires par spectrométrie gekoppelter Plasma-Massenspektrometrie (ICP-MS)
de masse avec plasma à couplage inductif (ICP-MS) nach Druckaufschluss
après digestion sous pression
This European Standard was approved by CEN on 5 June 2023.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17851:2023 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 5
5 Reagents . 5
6 Apparatus . 8
6.1 General . 8
6.2 ICP-MS. 8
7 Sampling . 8
8 Procedure. 8
8.1 Digestion . 8
8.2 Inductively coupled plasma mass spectrometry (ICP-MS). 9
8.2.1 ICP-MS working conditions . 9
8.2.2 Determination by ICP-MS . 9
8.3 Quality control of the analysis .10
9 Evaluation .11
9.1 Calculation of element contents in foodstuffs.11
9.2 Limits of quantification .11
9.3 Reliability of the procedure .12
10 Precision .12
10.1 General .12
10.2 Repeatability .12
10.3 Reproducibility .13
11 Test report .18
12 Explanations and notes .18
Annex A (normative) Potential spectral interferences of recommended Isotopes .19
Annex B (informative) Precision Data .23
Annex C (informative) Trueness of the procedure.38
Bibliography .39
European foreword
This document (EN 17851:2023) has been prepared by Technical Committee CEN/TC 275 “Food analysis
– Horizontal methods”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by January 2024, and conflicting national standards shall
be withdrawn at the latest by January 2024.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
1 Scope
This document specifies a procedure for the determination of Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl,
U and Zn in foodstuffs by inductively coupled plasma mass spectrometry (ICP-MS) after pressure
digestion.
The following foodstuffs were analysed for the elements listed in Table 1 in an interlaboratory study:
Banana (deep-frozen), Cocoa powder, Wheat noodle powder, Currant nectar (deep-frozen), Milk powder,
Oyster (dried), Celery (dried), Dogfish liver (dried), Liver (deep-frozen), Kale (dried).
a
Table 1 — Validated range
Mass fraction
mg/kg
Element
Lower range Upper range
Arsenic 0,02 36,6
Lead 0,004 0,58
Cadmium 0,006 15,2
Chromium 0,06 5,71
Cobalt 0,03 7,49
Copper 0,71 74,0
Manganese 0,31 73,5
Molybdenum 0,05 1,88
Nickel 0,11 11,0
Selenium 0,06 8,70
Silver 0,011 1,98
Thallium 0,008 0,12
Uranium 0,003 0,26
Zinc 1,8 1 582
a
Table 1 lists the ranges analysed in the interlaboratory study, indicating for each element the lowest and
highest content found in the ten analysed food matrices (see Annex B, Table B.1 to Table B.14).
The lower limit of the procedure’s range varies depending on the food matrix and the food’s water content.
It is a laboratory-specific value and is specified by the laboratory for each element when calculating the limit
of quantification (see 9.2).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 13804, Foodstuffs - Determination of elements and their chemical species - General considerations and
specific requirements
EN 13805, Foodstuffs - Determination of trace elements - Pressure digestion
EN 15765, Foodstuffs - Determination of trace elements - Determination of tin by inductively coupled
plasma mass spectrometry (ICP-MS) after pressure digestion
EN 17264, Foodstuffs - Determination of elements and their chemical species - Determination of aluminium
by inductively coupled plasma mass spectrometry (ICP-MS)
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
4 Principle
The sample is digested. For the digestion the pressure digestion process in EN 13805 shall be used, in the
case of foodstuffs with a low water content, after adding water. In the digestion solution, the elements
silver, arsenic, cadmium, cobalt, chromium, copper, manganese, molybdenum, nickel, lead, selenium,
thallium, uranium and zinc are quantified by ICP-MS. For this purpose, the digestion solution is nebulized
and the aerosol is transferred to an inductively coupled argon plasma where the elements are ionized.
The ions are transferred via a system of cones into a mass spectrometer, where they are separated
according to mass-to-charge ratio and detected by pulse and/or analogue detector.
The respective content of the elements mentioned in Clause 1 is understood as the total content
measured using this described procedure. It is expressed in mg/kg or mg/l, depending on the sample
type.
For other elements not specified within the scope, other documents can be considered, e.g. EN 15763. For
the determination of aluminium and tin in foodstuffs refer to EN 17264 and EN 15765.
5 Reagents
The chemicals, gases and water used shall be free enough from the elements to be determined to not
affect the results. Unless otherwise specified, “solutions” are understood to be aqueous solutions.
5.1 Nitric acid, mass fraction of min. ω = 65 %, density ρ ≈ 1,4 g/ml.
5.2 Stock solutions
A commercially available multi-element stock solution, for example with ρ = 10 mg/l, can be used for
silver, cadmium, cobalt, chromium, copper, manganese, molybdenum, nickel, lead, thallium, uranium and
for example with ρ = 100 mg/l for arsenic, selenium and zinc.
Alternatively, commercially available single-element stock solutions, for example with ρ = 1 000 mg/l,
can be used.
When using single-element stock solutions, attention shall be paid that they are suitable for ICP-MS, i.e.
are of sufficiently high purity, to generate no additional contamination with other elements to be
determined. If mixing the single-element stock solutions, attention shall also be paid to chemical
compatibility.
NOTE Depending on the manufacturer, stock solutions with 10 000 mg/l can also be used if they are available
in higher purities or have a better metrological traceability.
5.3 Multi-element standard solution
The dilutions of the stock solutions are depending on the concentration of the elements in the stock
solutions and the concentration of the elements in the calibration solutions.
The multi-element stock solution (5.2) is used to prepare a multi-element standard solution, e.g. with
ρ = 0,1 mg/l or ρ = 1,0 mg/l per element respectively. To prepare this standard solution, e.g.
approximately 10 ml water and 2 ml nitric acid (5.1) are filled into a 50-ml volumetric flask and mixed.
After cooling down to room temperature, 0,5 ml multi-element stock solution (5.2) is added using a
pipette and filled up with water.
The multi-element standard solution is stable for at least 1 month. The multi-element standard solution
containing silver shall be stored protected from light.
Alternatively, the multi-element standard solution can also be prepared from single-element stock
solutions by performing additional intermediate dilutions.
5.4 Stock solutions of internal standard, e.g ρ = 1 000 mg/l
When selecting internal standards, attention shall be paid that they cover the mass range of the analytes
and have an ionization energy similar to that of the elements to be corrected. Attention shall also be paid
that the concentration of the internal standards in the sample to be analysed is negligible and that they
are not interfered by sample constituents.
For example, rhodium, indium and lutetium have proved suitable as internal standards.
Alternatively, other elements may also be used as internal standards (see Annex A, Table A.2).
Scandium (Sc) is not suitable as internal standard due to interferences of Ca and Si molecular ions.
Internal standards with a mass below 100 m/z should not be used, because matrix constituents can
produce various interferences on the masses of such internal standards.
5.5 Standard solution of internal standard, e.g. ρ = 10 mg/l
To prepare this solution, approximately 10 ml water and 2 ml nitric acid (5.1) are filled into a 50-ml
volumetric flask and mixed. After cooling down to room temperature, 0,5 ml stock solution of internal
standard (5.4) is added using a pipette and filled up with water. This standard solution is stable for at
least three months.
5.6 Multi-element calibration solutions and Zero-point solution
5.6.1 General
The concentrations of the calibration solutions indicated below are exemplary and can be adapted
depending on the instrument sensitivity and the concentration range to be covered. Make sure that the
calibration is carried out within the linear range of the detector system. For calibration, at least
3 calibration solutions of different concentrations should be prepared. Make sure that the acid
concentration of the calibration solutions corresponds to the sample test solution.
The calibration solutions are prepared from the multi-element standard solution (5.3) by adding internal
standard (5.5) according to the following scheme:
To prepare these solutions, 10 ml to 20 ml water and 2 ml nitric acid (5.1) are filled into each 100 ml
volumetric flask and mixed. After cooling down to room temperature, the multi-element standard
solution (5.3) and 0,1 ml internal standard (5.5) are added one after the other using a pipette and then
filled up to the mark with water. The calibration solutions shall be freshly prepared each working day.
NOTE The acid concentration of the calibration solutions in the example is adapted to a digestion with 4 ml
nitric acid (5.1), a final volume of 20 ml and a dilution factor of 10 (in case of a dilution with water).
The internal standard solution can also be pumped via a separate channel of the tubing pump, mixed with
the calibration solution using a Y-piece and then nebulized. When using this type of addition, the internal
standard is not added to the calibration solution and shall be diluted accordingly. When using this
approach, attention shall be paid that the solutions are sufficiently mixed before they are nebulized and
that the pump rate of both channels is constant.
5.6.2 Calibration solution 1
It is prepared from the multi-element standard solution (5.3), for example as follows:
Pipette 0,5 ml multi-element standard solution (5.3) into the 100 ml volumetric flask prepared according
to 5.6.1 with water and nitric acid and follow the procedure described in 5.6.1.
ρ (silver, cadmium, cobalt, chromium, copper, manganese, molybdenum, nickel, lead, thallium and
uranium) = 0,5 µg /l, ρ (arsenic, selenium and zinc) = 5 µg/l and internal standard ρ = 10 µg /l. See also
Table 2.
5.6.3 Calibration solution 2
Pipette 1 ml multi-element standard solution (5.3) into the 100-ml volumetric flask prepared according
to 5.6.1 with water and nitric acid and follow the procedure described in 5.6.1.
ρ (silver, cadmium, cobalt, chromium, copper, manganese, molybdenum, nickel, lead, thallium and
uranium) = 1 µg /l, ρ (arsenic, selenium and zinc) = 10 µg/l and internal standard ρ = 10 µg /l. See also
Table 2.
5.6.4 Calibration solution 3
Pipette 2 ml multi-element standard solution (5.3) into the 100-ml volumetric flask prepared according
to 5.6.1 with water and nitric acid and follow the procedure described in 5.6.1.
ρ (silver, cadmium, cobalt, chromium, copper, manganese, molybdenum, nickel, lead, thallium and
uranium) = 2 µg /l, ρ (arsenic, selenium and zinc) = 20 µg/l and internal standard ρ = 10 µg /l. See also
Table 2.
5.6.5 Zero-point solution
The zero-point solution contains 2 ml nitric acid (5.1) and internal standard (in the same concentration
as the calibration solutions specified in 5.6) filled up with water to 100 ml. See also Table 2.
5.6.6 Tabulated overview of the calibration solutions and zero-point solution
Table 2 — Example of multi-element calibration solutions and zero-point solution
Calibration solution Volume of multi- Volume of internal Element
element standard standard solution concentration in the
a
solution (5.3) in 100 ml (5.5) in 100 ml calibration solution
in µg /l
Calibration solution 1 0,5 ml 0,1 ml 0,5
Calibration solution 2 1,0 ml 0,1 ml 1,0
Calibration solution 3 2,0 ml 0,1 ml 2,0
Zero point solution – 0,1 ml –
a
Concentration levels of arsenic, selenium and zinc are ten times higher.
6 Apparatus
6.1 General
All equipment and labware that come into direct contact with the sample and the solutions used shall be
carefully pre-treated/cleaned according to EN 13804 to minimize the blank value.
It is recommended to only use vessels of quartz glass, perfluoroalkoxy alkane (PFA), fluorinated ethylene
propylene (FEP) or polypropylene. It shall be ensured that the vessel materials do not release or absorb
specific elements to prevent inaccurate analysis results.
6.2 ICP-MS
The mass spectrometer shall include an inductively coupled argon plasma, sample supply and nebulising
system as well as instrument controlling and data acquisition. In order to avoid interferences of the
atomic mass of all elements listed in this procedure, it is necessary to use a mass spectrometer that is able
to eliminate or minimize interferences (e.g. reaction and/or collision cell, tandem MS, resolution above
4 000 m/z).
7 Sampling
The sampling procedure is not part of the procedure of analysis in this document.
The sampling shall be carried out in such a way to avoid any contamination with or loss of analytes.
8 Procedure
8.1 Digestion
The sample is mineralized with nitric acid, in the case of foodstuffs with a low water content, after adding
water, using the pressure digestion process described in EN 13805.
After the spontaneous reaction with the sample matrix caused by nitric acid has taken place, the digestion
vessel is closed and the pressure digestion process is started.
The digestion conditions depend on the manufacturer’s specifications, the reactivity of the sample, the
maximum pressure stability of the digestion vessels and the temperature reached.
NOTE Depending on the natural chloride content of the samples, the recovery of silver could be affected.
Therefore, the addition of hydrochloric acid (HCl) could be beneficial. However, additional interferences could be
occurring when using HCl.
The digestion solution obtained by pressure digestion is filled up to a specified volume, e.g. 20 ml. It can
be used for the subsequent element determination directly or after dilution. To minimize matrix effects,
e.g. signal suppression, a dilution factor of 10 is recommended, if a lower dilution is needed the dilution
factor should be at least 2,5. All sample test solutions shall have a similar concentration of acid and the
same concentration of internal standard as the calibration solutions.
8.2 Inductively coupled plasma mass spectrometry (ICP-MS)
8.2.1 ICP-MS working conditions
Set the instrument according to the manufacturer’s specifications and ignite the plasma. After sufficient
warming-up and stabilization of the instrument (approximately 20 min to 30 min), the settings are
optimized.
Select the instrument settings in such a way that not only high sensitivity is achieved, but also a low
amount of molecule ion interferences (e.g. oxide ratio, double charged ions).
For this purpose, an optimization solution is measured that contains e.g. Mg, Rh, Pb and Ce (ρ = 10 µg /l).
The formation rate of oxides and double charged ions should be lower than 3 %, for example, depending
on the recommendations of the instrument manufacturer.
If a collision or reaction cell is used in order to reduce polyatomic interferences, the flow rate of the cell
gas(es) should be optimized taking the matrix into account. When cell gases are used, the internal
standard, which is intended to be used for correction, shall be measured under that same conditions. The
recommendations of the instrument manufacturer shall be observed during optimization.
When applying different resolutions of the mass spectrometer, the mass windows shall be adjusted for
each of the selected resolutions to make sure that the isotope to be determined is positioned in the centre
of the window. At least one internal standard shall be measured at each resolution level.
Commercially available mass spectrometers often use different detectors or detector operating modes to
cover a larger linear concentration range. In such cases, it shall be ensured that the sensitivity transitions
of the detectors or operating modes are continuous and without any leaps.
8.2.2 Determination by ICP-MS
After optimizing the instrument, the measurements are started. It is recommended to use the isotopes
listed in Annex A to determine the analytes. Generally, only isotopes that are not prone to be affected by
interferences should be selected. To remove interferences, instrument systems should be used that are
capable of working with collision or reaction cells or with a higher physical resolution. If such corrections
are not possible, the interferences can also be reduced by using correction equations. For a plausibility
check of the interference corrections, simultaneous measurement of the uncorrected signals is advisable.
The interferences indicated in Annex A shall be taken into account.
The zero-point solution (5.6.5) and the calibration solutions (5.6.2 to 5.6.4) are measured and a
calibration curve is created from the count rates (counts/s) and concentrations. For complex matrices
and high total salt concentrations, using the standard addition procedure can be advantageous.
The linear range of the calibration function shall be determined and checked on a regular basis.
Spectrometer specific value: Resolution = m/(Δm). This information is given for the convenience of the users applying this
document.
Instrument specific unit.
The sample test solution is aspirated and measured. It is recommended that only diluted sample solutions
are measured (see 8.1). When preparing dilutions, attention shall be paid that the diluted sample test
solutions have the same concentration of acids and internal standard as the original sample test solutions
as well as the calibration solutions. The internal standard can be mixed with the sample test solution via
a separate channel of the hose pump using a Y-piece and then nebulized. In this case, no internal standard
is added to the test and calibration solutions. When using this approach, attention shall be paid that the
solutions are sufficiently mixed before they are nebulized and that the pump rate of both channels is
constant.
The measured count rate is converted into units of concentration using the calibration curve.
Depending on the matrix effects, the count rate of internal standards in individual sample test solutions
could be reduced or increased compared to that of pure calibration solutions.
If the count rate of the internal standards is reduced by more than 20 %, the filled-up digestion solution
should be diluted further. To recognize potential interference effects on the element contents measured
in the sample test solutions, measuring different dilutions of the filled-up digestion solution is generally
recommended.
If the count rate of the internal standards is increased by more than 20 %, the cause should be identified
as well. Continuous changes in intensity occur, for example, in the event of deposits on the sampling
cones. If the count rate is increased, it should also be checked whether the internal standard was not
already contained in the sample.
Matrix effects due to large amounts of salts (usually above 0,1 %) in the sample test solution can lead to
heavy deposits, for example on the sampling cone, causing so called memory effects in the sample
introduction system. In the case of samples with high element concentrations, attention shall therefore
be paid to adequate flushing before analysing the next sample test solution. The flush-out behaviour can
be checked with zero-point solution (5.6.5). Nevertheless, the signal of internal standard could decrease
up to 30 % in salt rich samples even if they are sufficiently diluted.
If the signal increase or decrease of more than 20 % is not caused by matrix effects other measures should
be taken into account, e.g. tuning or cleaning of the instrument.
In any case, the consistence of the calibration functions shall be checked at sufficient intervals (e.g. after
ten samples) by measuring a calibration solution. If necessary, the system shall be recalibrated.
8.3 Quality control of the analysis
For quality control, samples with reliably known contents of the analysed elements shall be analysed in
parallel to every measurement series, including all process steps, starting with digestion. Prepare and
measure blank solutions for every digestion series, also including all steps of the procedure.
It is recommended to use a certified reference material that is comparable to the sample in terms of
matrix and concentration range and has a low uncertainty interval.
9 Evaluation
9.1 Calculation of element contents in foodstuffs
The content ω is calculated for each element as mass fraction in milligrams per kilogram (Formula (1))
or litre (Formula (2)) of sample using:
aV××F
(1)
ω=
1 000×m
aV××F
ω= (2)
1 000×v
where
a is the element content in the sample test solution, in µg/l;
V is the volume of the filled-up digestion solution, in ml;
F is the dilution factor of the sample test solution;
m is the sample weight, in g;
v is the sample volume, in ml.
Factors of 1 000 required for unit conversion other than those shown above were cancelled with each
other in both formulae (for a more detailed representation, see sample calculation of limit of
quantification in 9.2).
Blank subtraction is not recommended. In the case of contaminations that have an influence on the
contents in the digestion solutions, the whole series shall be generally discarded. Before starting a new
digestion series, the source of contamination shall be identified and its cause eliminated.
9.2 Limits of quantification
The limit of quantification shall be calculated for each element. It is a laboratory-specific value and
depends on the following factors:
a) procedure used to calculate the limit of quantification;
b) food matrix and water content of the foodstuff;
c) sample weight and sample volume;
d) volume of the filled-up digestion solution;
e) vessel materials;
f) purity of the chemicals;
g) ICP-MS instrument;
h) technique;
i) laboratory environment.
The limit of quantification in foodstuffs is calculated according to the formulae specified in 9.1. The
element content in micrograms per litre of sample test solution obtained when calculating the limit of
quantification is used for a. The dilution factor is the minimum factor by which each sample is diluted
routinely, e.g. 10. Higher dilutions that are necessary due to too-high contents in the samples are not
taken into account in calculating the limit of quantification. Higher dilutions that become necessary due
to matrix effects shall be taken into account in calculating the limit of quantification.
Sample calculation of limit of quantification of lead in milk in mg/kg:
Example values: Calculated limit of quantification a: 0,05 µg /l test solution
Volume of the filled-up digestion 20 ml
solution V:
Dilution factor F: 10
Sample weight m: 2 g
Calculation using the example values with their units in the formula specified in 9.1 (Formula (1)):
0, 05 µg / l× 20 ml×10
ω 0,005 mg / kg
1 000× 2 g
More detailed representation of the calculation showing the unit conversion:
0,05 µg× 20 ml×10××1 l 1 mg×1 000 g
ω 0,005 mg / kg
1 l××2 g 1 000 ml×1 000 µg×1 kg
9.3 Reliability of the procedure
The present procedure was validated in a collaborative study (in 2017) with 18 participating
laboratories.
A total of eleven samples with ten different matrices (banana, cocoa powder, wheat noodles, currant
nectar, milk powder, oyster, celery, dogfish liver, liver, kale) were used, each with different contents of
the individual elements. The milk powder, oyster and dogfish liver are certified reference materials (see
Annex C).
In two of these eleven samples, the sample material was identical, namely wheat noodles. Each
quantitative value of a laboratory is obtained from duplicate measurement or, in the case of wheat
noodles (blind duplicate sample), from quadruplicate measurement.
10 Precision
10.1 General
Details of the inter-laboratory test of the precision of the procedures are summarized in Annex B. The
values derived from this test could not be applicable to analyte concentration ranges and matrices other
than given in Annex B.
10.2 Repeatability
The absolute difference between two independent single test results obtained using the same procedure
on identical test material in the same laboratory by the same operator using the same equipment within
a short time interval, will in no more than 5 % of the cases exceed the values of r given in Table 3.
==
==
10.3 Reproducibility
The absolute difference between two single test results obtained using the same procedure on identical
test material in different laboratories by different operators using the equivalent equipment will in no
more than 5 % of the cases exceed the values of R given in Table 3.
Table 3 — Precision data
Elements/ sample r R
x
in mg/kg in mg/kg in mg/kg
Arsenic
Banana 0,017 4 ± 0,002 3 0,002 7 0,012 7
Cocoa 0,140 ± 0,005 0,023 0,032
Liver 0,147 ± 0,006 0,021 0,035
Celery 0,192 ± 0,008 0,019 0,048
Wheat noodles 1 0,234 ± 0,012 0,024 0,070
Wheat noodles 2 0,230 ± 0,009 0,029 0,054
Currant nectar 0,404 ± 0,019 0,031 0,109
Kale 0,415 ± 0,021 0,070 0,126
Oyster 7,95 ± 0,13 0,68 0,87
Dogfish liver 36,6 ± 0,9 2,2 5,4
Cadmium
Banana 0,005 54 ± 0,000 34 0,002 11 0,002 45
Milk powder 0,011 5 ± 0,000 9 0,005 3 0,006 5
Liver 0,049 9 ± 0,001 2 0,008 1 0,009 0
Kale 0,106 ± 0,003 0,009 0,018
Wheat noodles 1 0,116 ± 0,003 0,016 0,020
Wheat noodles 2 0,120 ± 0,003 0,009 0,016
Cocoa 0,356 ± 0,008 0,027 0,051
Celery 0,696 ± 0,013 0,051 0,083
Currant nectar 1,02 ± 0,02 0,05 0,15
Oyster 2,65 ± 0,05 0,13 0,30
Dogfish liver 15,2 ± 0,4 0,7 2,5
Chromium
Currant nectar 0,052 2 ± 0,004 0 0,005 0 0,023 2
Banana 0,164 ± 0,019 0,052 0,118
Oyster 0,409 ± 0,019 0,060 0,113
Kale 1,15 ± 0,07 0,09 0,43
Elements/ sample r R
x
in mg/kg in mg/kg in mg/kg
Wheat noodles 1 1,26 ± 0,15 0,46 0,95
Wheat noodles 2 1,21 ± 0,11 0,54 0,76
Celery 1,62 ± 0,05 0,28 0,36
Dogfish liver 2,54 ± 0,16 0,44 1,02
Cocoa 5,71 ± 0,17 0,70 1,11
Cobalt
Banana 0,028 3 ± 0,000 8 0,002 4 0,005 0
Liver 0,055 8 ± 0,002 1 0,008 2 0,013 6
Celery 0,157 ± 0,005 0,014 0,030
Kale 0,191 ± 0,011 0,014 0,062
Dogfish liver 0,291 ± 0,008 0,021 0,047
Oyster 0,381 ± 0,010 0,030 0,061
Currant nectar 0,512 ± 0,012 0,017 0,066
Cocoa 1,71 ± 0,03 0,10 0,21
Wheat noodles 1 7,33 ± 0,33 0,70 2,03
Wheat noodles 2 7,49 ± 0,23 0,70 1,36
Copper
Banana 0,710 ± 0,022 0,052 0,137
Milk powder 1,07 ± 0,03 0,18 0,23
Wheat noodles 1 2,68 ± 0,10 0,47 0,68
Wheat noodles 2 2,69 ± 0,11 0,22 0,65
Currant nectar 6,08 ± 0,22 0,22 1,29
Celery 7,13 ± 0,21 0,52 1,28
Kale 15,2 ± 0,5 1,6 2,9
Liver 29,8 ± 0,7 3,5 4,6
Dogfish liver 37,6 ± 1,3 3,0 7,9
Cocoa 43,9 ± 0,7 2,8 4,5
Oyster 74,0 ± 2,0 4,3 12,0
Lead
Liver 0,003 71 ± 0,000 60 0,000 63 0,002 70
Milk powder 0,018 2 ± 0,002 3 0,004 0 0,012 7
Banana 0,021 9 ± 0,001 5 0,001 8 0,008 1
Currant nectar 0,058 6 ± 0,003 3 0,003 1 0,019 4
Elements/ sample r R
x
in mg/kg in mg/kg in mg/kg
Dogfish liver 0,172 ± 0,009 0,041 0,062
Wheat noodles 1 0,200 ± 0,007 0,011 0,040
Wheat noodles 2 0,203 ± 0,008 0,015 0,050
Oyster 0,305 ± 0,012 0,029 0,075
Kale 0,339 ± 0,018 0,024 0,105
Celery 0,435 ± 0,017 0,038 0,107
Cocoa 0,577 6 ± 0,021 0 0,041 7 0,127 9
Manganese
Milk powder 0,306 ± 0,014 0,051 0,093
Liver 1,91 ± 0,05 0,18 0,33
Banana 4,87 ± 0,08 0,26 0,50
Currant nectar 6,22 ± 0,14 0,29 0,84
Wheat noodles 1 8,61 ± 0,23 0,57 1,40
Wheat noodles 2 8,57 ± 0,23 0,40 1,37
Dogfish liver 9,67 ± 0,24 0,75 1,51
Oyster 19,2 ± 0,4 1,0 2,6
Celery 33,2 ± 1,0 2,8 6,5
Cocoa 50,3 ± 1,3 3,3 7,9
Kale 73,5 ± 2,5 6,5 14,7
Molybdenium
Banana 0,048 0 ± 0,002 1 0,006 7 0,013 1
Currant nectar 0,131 ± 0,003 0,010 0,018
Oyster 0,188 ± 0,008 0,031 0,053
Wheat noodles 1 0,297 ± 0,020 0,111 0,143
Wheat noodles 2 0,281 ± 0,016 0,046 0,097
Milk powder 0,360 ± 0,012 0,033 0,069
Celery 0,476 ± 0,018 0,039 0,109
Cocoa 0,488 ± 0,017 0,035 0,101
Liver 1,51 ± 0,04 0,11 0,26
Dogfish liver 1,57 ± 0,05 0,15 0,32
Kale 1,88 ± 0,06 0,11 0,36
Nickel
Banana 0,110 ± 0,010 0,021 0,060
Currant nectar 0,620 ± 0,015 0,045 0,090
Oyster 1,05 ± 0,03 0,11 0,20
Elements/ sample r R
x
in mg/kg in mg/kg in mg/kg
Celery 1,32 ± 0,02 0,14 0,15
Dogfish liver 1,82 ± 0,10 0,46 0,69
Wheat noodles 1 2,53 ± 0,06 0,45 0,45
Wheat noodles 2 2,55 ± 0,06 0,54 0,54
Kale 2,92 ± 0,07 0,36 0,51
Cocoa 11,0 ± 0,2 0,8 1,5
Selenium
Banana 0,054 0 ± 0,006 9 0,019 9 0,039 0
Cocoa 0,171 ± 0,019 0,025 0,099
Milk Powder 0,192 ± 0,014 0,039 0,072
Currant nectar 0,391 ± 0,020 0,043 0,112
Wheat noodles 1 0,446 ± 0,026 0,093 0,154
Wheat noodles 2 0,461 ± 0,031 0,082 0,180
Kale 0,484 ± 0,025 0,084 0,144
Liver 0,601 ± 0,031 0,087 0,180
Celery 0,643 ± 0,032 0,110 0,186
Oyster 2,25 ± 0,11 0,23 0,61
Dogfish liver 8,70 ± 0,40 0,91 2,33
Silver
Banana 0,010 7 ± 0,000 5 0,001 7 0,003 1
Currant nectar 0,027 5 ± 0,001 8 0,002 3 0,010 1
Celery 0,057 3 ± 0,001 2 0,003 1 0,006 8
Wheat noodles 1 0,111 ± 0,004 0,010 0,024
Wheat noodles 2 0,112 ± 0,004 0,009 0,023
Cocoa 0,184 ± 0,007 0,013 0,038
Liver 0,275 ± 0,006 0,013 0,035
Oyster 0,652 ± 0,020 0,030 0,110
Dogfish liver 1,98 ± 0,09 0,13 0,49
Thallium
Oyster 0,004 7 ± 0,000 7 0,001 0 0,003 4
Banana 0,007 55 ± 0,000 29 0,000 55 0,001 65
Currant nectar 0,010 2 ± 0,000 4 0,000 6 0,002 1
Dogfish liver 0,013 2 ± 0,000 8 0,003 0 0,005 1
Elements/ sample r R
x
in mg/kg in mg/kg in mg/kg
Cocoa 0,029 8 ± 0,001 3 0,002 9 0,007 6
Wheat noodles 1 0,057 4 ± 0,002 1 0,005 9 0,012 8
Wheat noodles 2 0,058 0 ± 0,002 5 0,009 1 0,015 9
Kale 0,070 5 ± 0,004 0 0,007 4 0,024 2
Liver 0,072 5 ± 0,002 0 0,004 9 0,012 2
Celery 0,125 ± 0,005 0,011 0,032
Uranium
Kale 0,002 93 ± 0,000 32 0,000 84 0,001 61
Banana 0,007 79 ± 0,000 41 0,001 23 0,002 44
Liver 0,014 3 ± 0,000 6 0,001 4 0,003 2
Currant nectar 0,019 8 ± 0,001 5 0,001 5 0,007 7
Celery 0,040 ± 0,001 8 0,004 1 0,010 6
Wheat noodles 1 0,075 6 ± 0,002 6 0,007 9 0,015 5
Wheat noodles 2 0,076 4 ± 0,002 5 0,003 8 0,013 8
Dogfish liver 0,086 1 ± 0,004 0 0,008 2 0,023 4
Cocoa 0,102 ± 0,004 0,013 0,024
Oyster 0,264 ± 0,008 0,013 0,044
Zinc
Banana 1,75 ± 0,11 0,24 0,70
Wheat noodles 1 9,55 ± 0,34 0,82 2,10
Wheat noodles 2 9,67 ± 0,37 1,22 2,29
Kale 21,9 ± 0,8 2,3 5,2
Celery 30,0 ± 1,3 2,1 7,4
Milk powder 45,9 ± 1,1 2,2 6,1
Liver 58,0 ± 1,6 5,2 10,3
Cocoa 74,0 ± 2,1 5,0 13,2
Currant nectar 80,9 ± 3,7 2,7 21,4
Dogfish liver 118,8 ± 3,9 9,8 23,9
Oyster 1582 ± 58 87 349
11 Test report
The test report shall specify at least the following:
a) all information necessary for the complete identification of the sample;
b) the test procedure used with reference to this document including its year of publication;
c) the results obtained, the units in which they are specified, including a reference to the clause which
explains how the results were calculated;
d) the date of the sampling (if known);
e) the date when the analysis was finished;
f) all operating details not specified in this document or regarded as optional, together with details of
any incidents occurred when performing the procedure which might have influenced the test results.
12 Explanations and notes
This procedure was developed by the “Element Analysis” working group of the Federal Office of
Consumer Protection and Food Safety to implement §. 64 LFGB and was validated in a collaborative study
with a total of 18 participants from 6 countries (see Annex B).
Potential interference effects were measured and investigated by the “Elements and Element Species”
working group of the German Chemical Society (GDCh) (see Annex A).
Annex A
(normative)
Potential spectral interferences of recommended Isotopes
For some elements, the effect of interferences with matrix solutions was investigated in different
laboratories and using different ICP-MS instruments. Therefore, two matrix solutions were measured
that represented simulated digestions (13 % nitric acid according to 5.1) and contained element
concentrations as they can occur in foodstuffs as a matrix. One solution contained 500 mg calcium/l,
200 mg magnesium/l, 500 mg potassium/l, 1 000 mg sodium/l, 1 400 mg chloride/l in the form of
hydrochloric acid and 3,3 % carbon. The other solution contained 300 mg phosphorus/l, 200 mg
sulphur/l, 200 mg fluorine/l, 800 mg potassium/l, 1 100 mg chloride/l in the form of hydrochloric acid
and 2,8 % carbon. These solutions were measured after dilution (see 8.1).
Observations from the test with simulated matrix solutions resulting from these investigations are listed
in the right column of Table A.1. A more detailed description of potential interferences can be found in
the Bibliography.
A great number of interferences can occur during ICP-MS determination of arsenic and selenium (see also
Table A.1), which cannot be removed in all cases. Problems occur in particular at low contents.
Table A.1 — Potential spectral interferences of recommended isotopes for the analysed
elements
Isotopic Interference
Mass Observations from
abundance Potential polyatomic removal by
Isobaric the test with
Element interferences at a using a
interferences simulated matrix
resolution of
resolution of 300
m/z in %
solutions
at least
40 12 + 40 12 + 36 16 +
Cr 52 83,8 Ar C , Ca C , Ar O , 4 000 Correction required
37 15 + 35 17 + 35 16 +
Cl N , Cl O , Cl OH ,
38 14 + 36 16 +
Ar N , S O
37 16 + 40 13 + 40 13 +
53 9,5 Cl O , Ca C , Ar C , 4 000 Correction required
38 15 + 36 16 +
Ar N , Ar OH
40 14 + 38 16 +
Mn 55 100 Ar NH , Ar OH , 4 000 Interferences can
39 16 + 40 14 + 37 18 +
K O , Ca NH , Cl O occur. The
interference effect
shall be
investigated,
corrections can be
required.
23 37 + 43 16 +
Ni 60 26,2 Na Cl , Ca OH , 4 000 The interference
24 36 +
Mg Ar effect shall be
investigated,
44 16 +
Ca O 10 000
corrections can be
46 16 + 23 39
...
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