🍎 Determination of lead, cadmium, zinc, copper, iron and chromium in foodstuffs by AAS after dry ashing — 10–20 g of sample is ashed in a platinum or quartz crucible with a temperature increase of at most 50 °C per hour to 450 °C, the ash is moistened with water and re-ashed until white or grey, dissolved with hydrochloric acid 6 mol/l, evaporated and dissolved in nitric acid 0.1 mol/l; zinc, copper and iron usually by flame, lead, cadmium and chromium usually by graphite furnace with the method of additions, PN-EN 14082 (withdrawn)

Food chemistry PN-EN 14082

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN 14082:2004 (Polish version), in full (our translation): “A method is specified for the determination of lead, cadmium, zinc, copper, iron and chromium content in foodstuffs by atomic absorption spectrometry (AAS) after dry ashing at 450 degrees C, applicable to various types of foodstuffs. It was successfully tested in interlaboratory studies with the participation of 16 laboratories. Foodstuffs such as composite diets, cereals, fish, fruit, liver and milk were used for the validation of the method”. We read the text of the standard in the sample of SIST EN 14082:2003 (the text of EN 14082:2003 without changes) from the title page through the contents, foreword and Clauses 1–5 up to and including the beginning of 6.3.3. Outside the sample remain Table 2 (graphite furnace parameters), Clause 7 (calculation), 8 (precision), 9 (test report) and Annex A (results of the interlaboratory test).

ACCORDING TO THE TEXT OF EN 14082:2003 (Clauses 1–5, 6.1–6.3.3). The standard was prepared by CEN/TC 275 “Food analysis — Horizontal methods” (secretariat DIN). Scope (1): lead, cadmium, zinc, copper, iron and chromium in foodstuffs, AAS after dry ashing at 450 °C; a method for various types of foodstuffs, tested in an interlaboratory trial with 16 laboratories on composite diets, cereals, fish, fruit, liver and milk; specific foodstuffs for which European Standards exist are excluded from this horizontal standard — it is the task of the analyst to check whether vertical standards exist. Normative reference (2): EN 13804 (performance criteria, general considerations and sample preparation). Principle (3): the sample is dry-ashed at 450 °C under a gradual increase in temperature, the ash is dissolved in hydrochloric acid, the solution evaporated to dryness, and the residue dissolved in nitric acid 0.1 mol/l; the metals are determined by flame or graphite furnace AAS. Warning: the standard may involve hazardous materials and operations; safety practices are established by the user. Reagents (4): the content of elements in reagents and water must not affect the result; hydrochloric acid at least 37 % (approx. 1190 mg/ml) and 6 mol/l (500 ml to 1000 ml); nitric acid at least 65 % (approx. 1400 mg/ml) and 0.1 mol/l (7 ml to 1000 ml); standard solutions 1000 mg/l — from metals or salts or commercial, preferably certified; examples: 1000 mg Pb in 7 ml of nitric acid, Cd, Zn and Fe — 1000 mg in 14 ml of water and 7 ml of acid, Cu — in 7 ml of acid, Cr — 3735 mg K2CrO4 in 7 ml of acid, to 1 l; calibration solutions in nitric acid 0.1 mol/l — for the graphite technique from the Pb, Cd, Cr solutions within the linear range, for the flame technique from the Zn, Cu, Fe solutions within the concentration range of the samples. Apparatus (5): glassware and plastic ware cleaned according to EN 13804; AAS with background correction, graphite furnace with autosampler and burners; lamps for each element (e.g. hollow cathode); programmable furnace with thermostat (450 ± 25) °C — with a non-programmable furnace a pre-ashing assembly is needed: hot plate up to about 300 °C, infrared lamp 250 W on a stand, ceramic plate, glass cover (e.g. crystallizing dish 185 mm × 100 mm) and wash-bottle with sulfuric acid for air purification; platinum or quartz crucibles 50–75 ml — quartz ones stored in nitric acid with water (1 + 9) and rinsed with deionized water before use, boiled with acid if necessary, platinum ones preferably heated red hot and boiled with acid; leak-proof plastic bottles 100 ml. Preparation (6.1): homogenization according to EN 13804. Ashing (6.2): test portion generally 10–20 g to the nearest 10 mg; an ashing aid may be used by the laboratory after its own validation. In a programmable furnace (6.2.1) the crucible is placed at a temperature not higher than 100 °C, the temperature raised by at most 50 °C per hour to 450 °C and left overnight; with a risk of heavy boiling drying is longer at a lower temperature. In a non-programmable furnace (6.2.2) the sample under the cover on the ceramic plate, swept by purified air, is dried with the infrared lamp at a distance of 30–40 cm and the hot plate at about 100 °C, moving the lamp closer as drying proceeds, then pre-ashed by stepwise raising the temperature to about 300 °C on the plate; then the crucible goes into the furnace at 200–250 °C and to 450 °C at most 50 °C per hour, overnight; a programmable furnace is preferable. Dissolution of the ash (6.2.3): after cooling moisten the ash with 1–3 ml of water, evaporate, put into the furnace at no more than 200 °C, raise stepwise to 450 °C and ash for 1–2 h or longer; repeat until the ash is white, grey or slightly coloured; add 5 ml of hydrochloric acid 6 mol/l so that it contacts all the ash, evaporate; dissolve the residue in an exact volume (10.0–30.0 ml) of nitric acid 0.1 mol/l, swirl the crucible with care, cover with a watch glass for 1–2 h, stir with a rod and transfer to the bottle; reagent blanks are treated like the samples. Caution: samples with a very high fat or sugar content are ashed with great care — fatty ones easily self-ignite, sugar-rich ones expand and can be lost; pre-ashing according to 6.2.2 is then recommended. AAS (6.3.1): the technique (flame or graphite furnace) is chosen according to the concentration; flame AAS is used whenever possible, as it is less sensitive to interference; Pb, Cd and Cr in foodstuffs generally require the graphite furnace, Zn, Cu and Fe can be determined by flame in most foodstuffs; background correction is always used, also for chromium, unless proven unnecessary; solutions are diluted with nitric acid 0.1 mol/l; contents are read from curves of at least 3 standards. Table 1 (example flame parameters): Zn — air–acetylene flame, oxidizing, 213.9 nm; Cu — as for Zn, 324.7 nm; Fe — according to the table nitrous oxide–acetylene flame, oxidizing, 248.3 nm. Graphite furnace (6.3.3): the method of additions is always used unless proven unnecessary — measurements with it must lie within the linear range; peak area is preferred to peak height; the temperature programme for ashing and atomization is optimized for each matrix.

STATUS (catalogue cards as of 03.10.2026). The card of PN-EN 14082:2004 (Polish version, published 17-08-2004, 19 pages, price group K) has the header “Withdrawn”: withdrawal date 13-02-2020; Food, Agriculture and Forestry Sector, KT 235 Food Analysis, ICS 67.050, “Introduces: EN 14082:2003 [IDT]”, “Supersedes: PN-EN 14082:2003 — English version”; the card has no “Replaced by” field, and the PKN search (term “PN-EN 14082”, 03.10.2026) shows no other editions — PKN indicates no successor. The card of PN-EN 14082:2003 (English version) — “Withdrawn” 17-08-2004, “Replaced by: PN-EN 14082:2004”; its Polish title and “Scope” field speak of “lithium, cadmium, zinc…” (Polish “lit”), although the English title and the text of the standard concern lead — this is a record of the card, not the content of the standard. In the iTeh catalogue (read 03.10.2026) the Slovenian adoption SIST EN 14082:2003 has the status “Withdrawn” dated 01.09.2020, without an indicated replacing document.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read 03.10.2026). The number 14082 appears in 8 records at 5 laboratories: AB 452, AB 531, AB 537, AB 560, AB 618. In the current scopes on the PCA website (read 03.10.2026, issues from 30.10.2025 to 24.09.2026) four give “PN-EN 14082:2004”, and AB 531 the designation alone without year, in a flexible scope, jointly with PN-EN 15550. The “Laboratories” tab (“PN-EN 14082”) shows the same 5 laboratories; checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (PCA items). Broad lists of food groups — meat, fish, milk, fruit and vegetables, cereals, mushrooms, beverages, coffee and tea, concentrates, confectionery, herbs and spices (AB 452, AB 537, AB 560, AB 618) — and feed and feed components in a flexible scope (AB 531, ETAAS). AB 531 gives “Metal content” without naming the elements. Cadmium and lead by graphite furnace (ETAAS) are determined by: AB 560 — Cd (0.0012–5.0) mg/kg, Pb (0.0065–5.0) mg/kg; AB 537 — Pb (0.005–5.0) mg/kg, Cd (0.001–2.0) mg/kg; AB 618 — Pb (0.002–2.0) mg/kg, Cd (0.0005–5.0) mg/kg. AB 618 also determines copper (0.5–10) mg/kg and zinc (0.2–30) mg/kg by flame. AB 452 gives in one item cadmium (0.003–2.0), lead (0.020–10.0), copper (0.005–50.0), zinc (0.005–50.0) and iron (0.01–500.0) mg/kg with the flame technique (FAAS) — for cadmium and lead the standard writes that in food they generally require the graphite furnace (6.3.1). None of the five laboratories determines chromium with this reference. Feed (AB 531) lies outside the scope of the text, which speaks of foodstuffs.

WHERE A SEEMINGLY CORRECT RESULT IS EASY. At ashing: a temperature increase faster than 50 °C/h does not meet 6.2.1, and fatty samples may ignite, sugar-rich ones swell and escape from the crucible, which causes losses without a trace in the result (caution in 6.2.3); unburnt black ash does not meet the condition of 6.2.3. At vessels: quartz and platinum crucibles without acid preparation and poorly cleaned glassware give metal in the blank (5.1, 5.10). At measurement: background correction is mandatory — also for chromium — unless proven unnecessary; in the graphite furnace the method of additions is always used unless proven unnecessary, and only within the linear range (6.3.1, 6.3.3). At the result: the standard is horizontal — it does not apply to products with their own European Standard (1); the test portion mass and final volume (10.0–30.0 ml) enter the calculation, whose clause we did not read.

WHAT WE DO NOT GIVE. We did not read Table 2, Clauses 7–9 and Annex A, so we do not give the graphite furnace parameters, the calculation formula, precision data or the content of the test report. We did not read EN 13804 and PN-EN 15550 for this entry. We do not give maximum levels of metals in food, because we did not read the texts of regulations for this entry.

Method principle

The organic matter of a food sample is burned dry in a crucible, raising the temperature slowly (at most 50 °C per hour) to 450 °C; the ash is dissolved with hydrochloric acid, evaporated, and the residue dissolved in nitric acid 0.1 mol/l. In the solution the absorption of radiation characteristic of each element is measured — in a flame (Zn, Cu, Fe) or in a graphite furnace by the method of additions (Pb, Cd, Cr), with background correction.

Applications

• Various types of foodstuffs — lead, cadmium, zinc, copper, iron, chromium; validation on composite diets, cereals, fish, fruit, liver and milk (Clause 1)
• Not applicable to products for which a separate European Standard exists — the analyst checks this (Clause 1)
• Cadmium and lead (four laboratories), copper and zinc (two), iron (one) in broad food groups — in the accreditation scopes of 5 laboratories at PCA; feed — at one, outside the scope of the text

Key parameters

Standard

Standard number

PN-EN 14082:2004

Title (PL)

Artykuły żywnościowe — Oznaczanie pierwiastków śladowych — Oznaczanie zawartości ołowiu, kadmu, cynku, miedzi, żelaza i chromu metodą atomowej spektrometrii absorpcyjnej (AAS) po mineralizacji suchej

Title (EN)

Foodstuffs — Determination of trace elements — Determination of lead, cadmium, zinc, copper, iron and chromium by atomic absorption spectrometry (AAS) after dry ashing

Step-by-step procedure

1. Homogenization and test portion

   According to EN 13804; 10–20 g into the crucible, to the nearest 10 mg. PN-EN 14082:2004 withdrawn 13-02-2020 (PKN catalogue card as of 03.10.2026).

2. Drying and ashing

   Programmable furnace: from ≤ 100 °C, ≤ 50 °C/h to 450 °C, overnight. Non-programmable furnace: drying with IR lamp and hot plate, pre-ashing to approx. 300 °C, then furnace from 200–250 °C to 450 °C. Fatty and sugar-rich samples — with care, with pre-ashing.

3. Re-ashing

   Moisten the ash with 1–3 ml of water, evaporate, from ≤ 200 °C to 450 °C for 1–2 h; repeat until the ash is white or grey.

4. Dissolution

   5 ml HCl 6 mol/l, evaporate; dissolve in 10.0–30.0 ml HNO3 0.1 mol/l, 1–2 h under a watch glass, stir, into the bottle; reagent blanks like the samples.

5. AAS measurement

   Zn, Cu, Fe — flame; Pb, Cd, Cr — graphite furnace, method of additions, peak area; background correction; at least 3 standards. Calculation (Clause 7) outside the sample read.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard may involve hazardous materials and operations — safety practices are established by the user (warning in Clause 3)
• Fatty samples may self-ignite in the furnace (caution in 6.2.3); concentrated acids and potassium chromate (carcinogenic) — gloves, goggles, fume hood
• Nitrous oxide–acetylene and air–acetylene flame — safety rules for flammable gases according to the spectrometer instructions

Frequently asked questions