🍎 Determination of cadmium and lead in animal feeding stuffs by graphite furnace atomic absorption spectrometry (GF-AAS) after pressure digestion — about 0.5 g of sample is digested with 3 ml of nitric acid (in a microwave also with 0.5 ml of hydrogen peroxide) in a pressure vessel, the solution is diluted and measured at 228.8 nm (Cd) and 283.3 nm (Pb) with background correction and a palladium–magnesium modifier against matrix-matched external calibration; extractable lead in minerals and feeds with phyllosilicates — boiling 2 g with diluted nitric acid, PN-EN 15550

Food chemistry PN-EN 15550

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of SIST EN 15550:2017 (English text of EN 15550:2017): from the title page through the contents, European foreword and Clauses 1–8 to 9.4.2 (determination in the graphite furnace, Table 1 and notes on wavelengths) on page 9. Outside the sample remain the calculation (10), precision (11), test report (12), Annexes A (results of the inter-laboratory tests) and B (notes on the detection technique, interferences, quantification and pressure digestion) and the bibliography.

ACCORDING TO THE TEXT OF EN 15550:2017. The standard was prepared by CEN/TC 327 “Animal feeding stuffs: Methods of sampling and analysis”, whose secretariat is held by NEN; national implementation was due by February 2018 at the latest; the document supersedes EN 15550:2007; warning — the method uses reagents hazardous to health, and protective measures are the user’s responsibility. Scope (1): determination of cadmium and lead in animal feeding stuffs by GF-AAS after pressure digestion; the method was successfully tested in the range 0.015–5.65 mg/kg for Cd and 0.18–40.3 mg/kg for Pb in 11 feeds: 2 complete feeds (pig feed, sheep feed), 2 complementary (mineral) feeds, 1 mineral premixture, 4 feed materials (MgO, 2 phosphates, CaCO3) and 2 feed additives (CuSO4, bentonite); for extractable lead in minerals and feeds containing phyllosilicates (e.g. kaolinite clay), wet digestion with diluted nitric acid should be used; the limit of quantification depends on the matrix and the instrument — for cadmium 0.05 mg/kg should normally be obtained, for lead 0.5 mg/kg. References (2): EN ISO 3696, EN ISO 6498. Terms (3): limit of detection (LOD), limit of quantification (LOQ) — the lowest concentration determined with satisfactory measurement uncertainty; according to notes, the precision is arbitrarily defined as a relative standard deviation of 10 %, and the limit is usually set as a multiple (e.g. 3.3) of the detection limit; feed additives according to Regulation (EC) No 1831/2003, animal feeding stuffs according to Regulation (EC) No 178/2002. Principle (4): a test portion is digested under pressure, and element concentrations are determined by GF-AAS with external calibration; the detection limit depends on the matrix, instrument, atomizer type and modifiers; a typical injection volume is 10–20 µl. Reagents (5): analytical grade, water of grade 2 according to EN ISO 3696; concentrated nitric acid at least 65 % (about 1.42 g/ml); hydrogen peroxide at least 30 %; Cd and Pb stock solutions 1000 mg/l (certified ones advisable, not used after expiry); calibration solutions with a blank in the linear range, matrix-matched (e.g. acid concentration as in the samples); modifier, e.g. palladium nitrate with magnesium nitrate (10 µl = 15 µg Pd and 10 µg Mg(NO3)2, for not longer than one week); argon at least 99.99 %. Apparatus (6): grinders that do not contaminate the sample (to ≤ 0.5 mm, for mineral matrices ≤ 0.5 mm or ≤ 0.1 mm), mortar, balance 1 mg; pressure digestion apparatus — tested for safety, with acid-resistant vessels of low contamination; instead of PTFE, quartz, FEP or PFA holders are better, and above 230 °C quartz; graphite furnace AAS with background correction (e.g. Zeeman), autosampler, hollow cathode or EDL lamps for Pb and Cd, with an exhaust over the furnace; pyrolytically coated graphite tubes, preferably with platforms; freeze-drier; drying oven (70 ± 5) °C; flasks 100 and 1000 ml; 250 ml beaker; hot plate with temperature control. Sampling (7): not part of the method — a recommended method is in EN ISO 6497. Preparation (8): according to EN ISO 6498, grinding without heating, as quickly as possible; feeds — usually 500 g to ≤ 0.5 mm; liquid feeds — pre-drying at (70 ± 5) °C for at least 16 h or freeze-drying, weighing before and after; mineral matrices to ≤ 0.5 mm, but products containing crystalline water (e.g. MgCl2·6H2O) should not be ground. Digestion (9.1): the sample mass is matched to the vessel capacity, strictly following the manufacturer’s instructions, and temperature and time are set according to EN 13805 and Annex B; microwave example — about 0.5 g (to 1 mg) in a 70–100 ml vessel, 3 ml HNO3 and 0.5 ml H2O2, about 30 min pre-digestion outside the microwave, then e.g. 100 W → 600 W in 5 min, 5 min hold, 1000 W for 10 min, cooling for at least 20–25 min; high-pressure example — about 0.5 g, 3 ml HNO3, 70 ml vessel, to 150 °C in 60 min, to 300 °C in 40 min, 90 min at 300 °C; a blank treated the same way. Extractable lead (9.2): about 2 g in a 250 ml beaker, 16 ml of 1 + 1 nitric acid and about 70 ml of water, boiling for 30 min under a watch-glass, transfer to a 100 ml flask, filtration through a dry folded filter discarding the first portion; a blank treated the same way. Calibration (9.3): external, preferably a blank and five equidistant solutions, matrix-matched; for unknown matrix effects — standard addition; measurements in the linear range. Determination (9.4): before operation, analytical lines, selectivity, detection and quantification limits, precision, linear range and interferences are established; the furnace programme usually has four steps — drying, pyrolysis, atomisation, cleaning; Table 1 (general guidelines): Cd — 228.8 nm, slit 0.7 nm, pyrolysis 300 °C without modifier / 900 °C with modifier, atomisation 1250 / 1600 °C; Pb — 283.3 nm, 0.7 nm, pyrolysis 600 / 1200 °C, atomisation 1500 / 2000 °C; it is recommended to start from the manufacturer’s temperatures and to evaluate new matrices with ash/atomise curves; during atomisation the argon flow should be interrupted; background correction should always be used; alternative lines may be used — for lead, 217.0 nm has about twice the sensitivity of 283.3 nm, but higher noise and greater risk of interferences.

STATUS (as of 03.10.2026). The PKN search (query “PN-EN 15550”, 03.10.2026) shows PN-EN 15550:2017-09 (English version, “Wprowadza: EN 15550:2017 [IDT]”) without a withdrawal note, and the withdrawn PN-EN 15550:2009 (Polish version, replaced by PN-EN 15550:2017-09) and PN-EN 15550:2007 (English version); the fourth result is the withdrawn PN-ISO 15550:2009 on internal combustion engines. In the iTeh catalogue (read on 03.10.2026) EN 15550:2017 has the status “Published”, stage 90.93 (decision to confirm the standard).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 03.10.2026). The number 15550 appears in 4 records at 4 laboratories: AB 527, AB 531, AB 856, AB 868. In the current PCA documents (read on 03.10.2026, issues from 21.11.2025 to 02.07.2026) the number appears in 3 rows — one each at AB 531, AB 856 and AB 868; the current AB 527 document (issue No 26 of 02.07.2026) does not contain the number 15550, and the record in the database copy (“PN-EN 15550”, metal content in feeds, premixes and feed additives, ETAAS) has no counterpart in that issue; in each of the four documents the number of page markers equals the number of PDF pages, without repetitions; a search of all 1291 PCA documents downloaded from BIP on 03.10.2026 found no laboratories outside the database copy (17 laboratories in the register have no link to a scope document on BIP). Form in PCA: “PN-EN 15550” without year together with PN-EN 14082 (AB 531), “PN-EN 15550:2017” (AB 856), “PN-EN 15550:2017-09” together with instruction I-01/1 edition 7 of 01.02.2022 (AB 868). None of these items is suspended. The “Laboratories” tab (query “PN-EN 15550”) shows 4 laboratories, including AB 527, whose current scope document does not contain this standard — checked with a tab query on the labcoda.pl production server on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Test object: feeds and feed components (AB 531, item in a flexible accreditation scope), feed materials, compound feeds, premixes (AB 856), animal feeds (AB 868). Characteristic: metal content (AB 531), cadmium and lead content (AB 856, AB 868). Ranges: cadmium 0.010–6.00 mg/kg and lead 0.050–50.0 mg/kg (AB 856), cadmium (0.020–0.100) mg/kg and lead (0.10–0.60) mg/kg (AB 868); AB 531 gives no range. Technique: atomic absorption spectrometry with electrothermal atomisation (ETAAS) at all three (at AB 856 called flameless).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. At the matrix: in minerals and feeds with phyllosilicates, extractable lead is determined after boiling with 1 + 1 nitric acid, not after pressure digestion (1, 9.2). At grinding: products with crystalline water should not be ground (8.4). At vessels: sample mass according to vessel capacity and manufacturer’s instructions; above 230 °C — quartz (6.3, 9.1.2). At calibration: matrix matching (e.g. acid concentration), and for unknown matrix effects — standard addition (5.4, 9.3). At measurement: background correction always, argon flow interrupted during atomisation, pyrolysis and atomisation temperatures depending on the modifier (9.4.2, Table 1). At the range: the method was tested for Cd 0.015–5.65 and Pb 0.18–40.3 mg/kg (1) — the upper lead limit at AB 856 (50.0 mg/kg) lies above the tested range, and the lower lead limits at AB 856 (0.050 mg/kg) and AB 868 (0.10 mg/kg) below the quantification limit of 0.5 mg/kg that according to the scope should normally be obtained.

WHAT WE DO NOT GIVE. We did not read the calculation formula, the precision data (11, Annex A) or the notes in Annex B. We do not give maximum permitted cadmium and lead contents in feed.

Method principle

About 0.5 g of prepared feed is digested with nitric acid (in microwave digestion also with hydrogen peroxide) in a closed pressure vessel. The diluted solution is injected (10–20 µl) into a graphite tube, and the absorption of cadmium at 228.8 nm and lead at 283.3 nm is measured with background correction and a matrix modifier, against matrix-matched external calibration or by standard addition. Extractable lead in minerals with phyllosilicates is determined after boiling 2 g of sample for 30 min with 1 + 1 nitric acid.

Applications

• Cadmium and lead in complete, complementary and mineral feeds, premixes, feed materials and additives (tested on 11 feeds) (1)
• Extractable lead in minerals and feeds with phyllosilicates, e.g. kaolinite clay (1, 9.2)
• Feeds, feed components and materials, compound feeds, premixes — items in the accreditation scopes of 3 laboratories in the current PCA documents

Key parameters

Standard

Standard number

PN-EN 15550:2017-09

Title (PL)

Pasze: Metody pobierania próbek i analiz — Oznaczanie kadmu i ołowiu metodą absorpcyjnej spektrometrii atomowej z zastosowaniem kuwety grafitowej (GF-AAS) po mineralizacji ciśnieniowej

Title (EN)

Animal feeding stuffs: Methods of sampling and analysis — Determination of cadmium and lead by graphite furnace atomic absorption spectrometry (GF-AAS) after pressure digestion

Step-by-step procedure

1. Sample

   EN ISO 6498; grinding to ≤ 0.5 mm, liquid feeds pre-dried or freeze-dried, minerals with crystalline water not ground (8). PN-EN 15550:2017-09 without a withdrawal note (03.10.2026).

2. Digestion

   About 0.5 g with HNO3 (and H2O2) under pressure; blank (9.1). For extractable lead — boiling with HNO3 1 + 1 (9.2).

3. Calibration

   Blank + 5 matrix-matched solutions or standard addition (9.3).

4. GF-AAS

   Drying, pyrolysis, atomisation (argon stopped), cleaning; Cd 228.8 nm, Pb 283.3 nm, background correction (9.4.2).

5. Result

   Calculation according to Clause 10 (not read).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The method uses reagents hazardous to health — protective measures are the user’s responsibility (foreword, 5)
• Pressure vessels — only safety-tested apparatus and sample mass according to the manufacturer’s instructions (6.3, 9.1.2)
• Exhaust over the graphite furnace to remove smoke and vapours (6.4, note)

Frequently asked questions