FprEN 17851

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

General Information

• Status: Not Published
• Publication Date: 28-Jun-2023
• ICS: 67.050 - General methods of tests and analysis for food products
• Technical Committee: CEN/TC 275 - Food analysis - Horizontal methods
• Drafting Committee: CEN/TC 275/WG 10 - Trace elements (heavy metals)
• Current Stage: 5060 - Closure of Vote - Formal Approval
• Start Date: 04-May-2023
• Due Date: 31-Jan-2024
• Completion Date: 04-May-2023
• Ref Project: kSIST FprEN 17851:2023 - 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

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN 17851:2022
01-julij-2022

Analiza živil - 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

Analysis of Foodstuffs - 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 ICP-MS nach
Druckaufschluss

Analyse des produits alimentaires - Dosage 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: prEN 17851
ICS:
67.050 Splošne preskusne in General methods of tests and
analizne metode za živilske analysis for food products
proizvode
oSIST prEN 17851:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 17851:2022
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oSIST prEN 17851:2022
DRAFT
EUROPEAN STANDARD
prEN 17851
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2022
ICS 67.050
English Version
Analysis of Foodstuffs - 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

Analyse des produits alimentaires - Dosage des Lebensmittel - Bestimmung von Elementen und ihren

éléments Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Tl, U Verbindungen - Bestimmung von Ag, As, Cd, Co, Cr, Cu,

et Zn dans les produits alimentaires par spectrométrie Mn, Mo, Ni, Pb, Se, Tl, U und Zn mit ICP-MS nach

de masse avec plasma à couplage inductif (ICP-MS) Druckaufschluss
après digestion sous pression

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 275.

If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, Turkey and

United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17851:2022 E

worldwide for CEN national Members.
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Contents Page

European foreword ....................................................................................................................................................... 3

1 Scope .................................................................................................................................................................... 4

2 Normative references .................................................................................................................................... 4

3 Terms and definitions ................................................................................................................................... 5

4 Principle ............................................................................................................................................................. 5

5 Reagents ............................................................................................................................................................. 5

6 Apparatus ........................................................................................................................................................... 7

6.1 General ................................................................................................................................................................ 7

6.2 ICP-MS.................................................................................................................................................................. 8

7 Sampling ............................................................................................................................................................. 8

8 Procedure........................................................................................................................................................... 8

8.1 Digestion ............................................................................................................................................................ 8

8.2 Inductively coupled plasma mass spectrometry (ICP-MS)............................................................... 8

8.3 Quality control of the analysis ................................................................................................................. 10

9 Evaluation ....................................................................................................................................................... 10

9.1 Calculation of element contents in foodstuffs.................................................................................... 10

9.2 Limits of quantification .............................................................................................................................. 10

9.3 Reliability of the method ........................................................................................................................... 11

10 Precision .......................................................................................................................................................... 11

10.1 General ............................................................................................................................................................. 11

10.2 Repeatability .................................................................................................................................................. 12

10.3 Reproducibility ............................................................................................................................................. 12

11 Test report ...................................................................................................................................................... 17

12 Explanations and notes .............................................................................................................................. 17

Annex A (normative) Potential spectral interferences of recommended Isotopes .......................... 18

Annex B (informative) Precision Data ............................................................................................................... 22

Annex C (informative) Trueness of the method ............................................................................................. 37

Bibliography ................................................................................................................................................................. 38

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European foreword

This document (prEN 17851:2022) has been prepared by Technical Committee CEN/TC 275 “Food

analysis – Horizontal methods”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
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1 Scope

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 — 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

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 method’s range varies depending on the food matrix and the food’s water content. It is

a laboratory-specific value and is defined 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
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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 using the pressure digestion process described in EN 13805, 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 sampling 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 method. It is expressed in mg/kg or mg/l, depending on the sample type.

EN 17264 and EN 15765 shall be referred to for the determination of aluminium and tin in foodstuffs.

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, ω = at least 65 %, density = approximately 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.
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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, exactly 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 trace 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 Table 2 and Annex A).

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 may

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, exactly 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 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

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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 with water and nitric acid and follow the procedure described in 5.6.

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.

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 with water and nitric acid and follow the procedure described in 5.6.

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.

5.6.4 Calibration solution 3

Pipette 2 ml multi-element standard solution (5.3) into the 100-ml volumetric flask prepared according

to 6.6 with water and nitric acid and follow the procedure described in 5.6.

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.

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.
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
solution (5.3) (5.5) calibration solution
in 100 ml in 100 ml 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 –
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.
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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 method, 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 method of analysis defined in this official method.

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 could be beneficial. Also, in case of using HCl additional interferences

could be occurring.

The digestion solution obtained by pressure digestion is filled up to a defined volume, e.g. 20 ml. It can be

used for the subsequent element determination directly or after dilution. To minimize the signal

suppression, dilution by a factor of ten, but at least by a factor of 2,5, is recommended. All test solutions

shall have a similar concentration of acid and exactly 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 stabilisation 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. The recommendations of the instrument

manufacturer shall be observed during optimization. When cell gases are used, they shall also be applied

to at least one internal standard and the correction shall be carried out with that internal standard.

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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 able to ensure 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, 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) are measured and a calibration curve

is created from the count rates (counts/sec) and concentrations. For complex matrices and high total salt

concentrations, using the standard addition method may be advantageous.

The linear range of the calibration function shall be determined and checked on a regular basis.

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 test solutions

have the same concentration of acids and internal standard as the original test solutions as well as the

calibration solutions. The internal standard can be mixed with the 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 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 digestion solution should be

diluted further. To recognize potential interference effects on the element contents measured in the test

solutions, measuring different dilutions of the 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 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 test solution. The flush-out behaviour can be checked with

zero-point solution (5.6.5).

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.

Spectrometer specific value: Resolution = m/(delta-m). This information is given for the convenience of the users applying this

document.
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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
ω= (1)
1 000×m
aV××F
ω= (2)
1 000×v
where
a is the element content in the test solution, in micrograms per litre;
V is the volume of the sample test solution after digestion, in millilitres;
F is the dilution factor of the test solution;
m is the sample weight, in grams;
v is the sample volume, in millilitres.

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) method used to calculate the limit of quantification;
b) food matrix and
...