🍎 Determination of calcium, sodium, phosphorus, magnesium, potassium, sulphur, iron, zinc, copper, manganese and cobalt in animal feeding stuffs by inductively coupled plasma atomic emission spectrometry (ICP-AES) 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), the solution diluted and emission measured at the lines in Table 1 with matrix-matched external calibration or standard addition; molybdenum, lead, cadmium and arsenic only after in-house validation; quantification limit normally 1 mg/kg, PN-EN 15621

Food chemistry PN-EN 15621

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of SIST EN 15621:2017 (English text of EN 15621:2017): from the European foreword through Clauses 1–9 to 10.3 (standard addition with one addition, equation (3)) on page 11. Outside the sample remain the rest of the calculation, precision, test report, Annexes A (results of the interlaboratory study) and B (notes on the technique) and the bibliography.

ACCORDING TO THE TEXT OF EN 15621:2017. 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 15621:2012; warning — the method uses reagents hazardous to health, and protective measures are the user’s responsibility. Scope (1): determination of Ca, Na, P, Mg, K, S, Fe, Zn, Cu, Mn and Co in animal feeding stuffs by ICP-AES after pressure digestion; the method was fully statistically tested for these elements in 11 feeds: 2 complete feeds (pig, sheep), 3 complementary (mineral) feeds, 1 mineral premixture, 3 feed materials (MgO, phosphate, CaCO3) and 2 feed additives (CuSO4, bentonite); for elements with HORRAT values above 2 (e.g. potassium and sulphur, Annex A) the method is more applicable for screening than for confirmation; molybdenum, lead, cadmium and arsenic were not fully evaluated because in most samples they were below the quantification limit — for them a single-laboratory validation is necessary; extractable lead in minerals and feeds containing phyllosilicates (e.g. kaolinite clay) should be determined after wet digestion with nitric acid; the quantification limit depends on matrix and instrument, the method is not applicable to low concentrations — normally 1 mg/kg should be obtained; according to notes, the method can also be used for products with high mineral content (> 5 %), checking accuracy individually, and results may be higher than with EN 15510 because pressure digestion is used. References (2): EN ISO 3696, EN ISO 6498. Terms (3): as in European legislation. Principle (4): a test portion is digested under pressure, and the concentrations of Ca, Na, P, Mg, K, S, Fe, Zn, Cu, Mn, Co, Mo, Pb, Cd and As are determined by ICP-AES with external calibration or standard addition. Reagents (5): analytical grade, water of grade 2; concentrated nitric acid at least 65 % (about 1.42 g/ml); nitric acid 2 % (v/v); hydrogen peroxide at least 30 %; stock solutions of the 15 elements 1000 mg/l (certified ones advisable); multi-element standard solutions taking into account chemical compatibility, hydrolysis and spectral interferences, diluted with the same acid at the same concentration as the test solution, stable for several months in the dark. Apparatus (6): according to a note, glassware is not advisable for low sodium concentrations (a source of sodium); grinders to ≤ 0.5 mm (e.g. knife mill) and ≤ 0.1 mm (e.g. ball mill); balance 1 mg; pressure digestion apparatus — tested for safety, with acid-resistant vessels of low contamination by the elements determined; quartz, FEP or PFA better than PTFE, and quartz above 230 °C; ICP-AES spectrometer with at least radial plasma (axial equally acceptable), background correction when necessary and working conditions optimized according to the manufacturer; freeze-drier; oven (70 ± 5) °C; 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 and without contamination by the tools, as quickly as possible; since at most 0.5 g is used for digestion, sample homogeneity is of utmost importance; 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; minerals to ≤ 0.5 mm, but products containing crystalline water (e.g. MgCl2·6H2O) should not be ground. Digestion (9.1): sample mass according to vessel capacity and the manufacturer’s instructions, temperature and time according to EN ISO 13805 and Annex B; microwave example — about 0.5 g (to 1 mg) in a 100 ml vessel, 3 ml HNO3 and 0.5 ml H2O2, about 30 min pre-digestion, then e.g. 100 W → 600 W in 5 min, 5 min, 1000 W for 10 min, cooling 20–25 min; high-pressure example — 3 ml HNO3, to 150 °C in 60 min, to 300 °C in 40 min, 90 min at 300 °C; a blank treated the same way; the diluted solution is the test solution. Extractable lead (9.2): 2 g, 16 ml HNO3 1 + 1 and about 70 ml water, 30 min boiling under a watch glass, to 100 ml, filtration discarding the first portion. Calibration (9.3): external or standard addition; the curve normally linear (a non-linear one acceptable if well described, but not with standard addition); matrix matching for external calibration; at least a blank and one standard, and if non-linear — a blank and at least three equidistant standards; standard addition — at least two points, and near the quantification limit four (three additions, the highest 3–5 times the concentration in the solution). Determination (9.4): lines, selectivity, limits, precision, linear range and interferences are established before operation; Table 1 gives emission lines and possible interferences, e.g. for sodium 330.237, 588.995 and 589.592 nm, and other lines are allowed; blank, standards and test solution are introduced in ascending order, at least two replicates, averaging, rinsing with water or 2 % HNO3 after each measurement; residue in the solution — decanting into the tube. Calculation (10): net signal — counts per second at the selected line after background correction; external calibration with one standard: S = c · b + a, c = (S − a)/b; standard addition with one addition: c = S0 · Vs · cs / ((S1 − S0) · Vf).

STATUS (as of 03.10.2026). The PKN search (query “PN-EN 15621”, 03.10.2026) shows PN-EN 15621:2017-09 (English version, “Wprowadza: EN 15621:2017 [IDT]”) without a withdrawal note and the withdrawn PN-EN 15621:2012, replaced by PN-EN 15621:2017-09; the other results are PN-EN ISO 15621 standards on absorbent products. In the iTeh catalogue (read on 03.10.2026) EN 15621:2017 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 15621 appears in 5 records at 3 laboratories: AB 531 (3), AB 545, AB 594. In the current PCA documents (read on 03.10.2026, issues from 31.10.2025 to 17.06.2026) the number appears in 5 rows — 3 at AB 531 and one at each of the others; in each of the three 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 at all: “PN-EN 15621:2017-09”. None of these items is suspended. In the AB 594 document the test object of the item with this standard is feeds, while the database copy assigns it to fish and fish products from the adjacent row. The “Laboratories” tab (query “PN-EN 15621”) shows all 3 laboratories — checked with a tab query on the labcoda.pl production server on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). AB 545 — feeds: phosphorus (0.012–23.0) %, magnesium (0.047–60.0) %, potassium (0.033–50.0) %, sodium (0.0025–40.0) %, calcium (0.040–40.0) %, copper (3.7–30 700) mg/kg, zinc (2.8–800 000) mg/kg, manganese (4.7–68 000) mg/kg, iron (3.2–300 000) mg/kg. AB 594 — feeds: Fe (0.7–19 600), Cu (4.53–6690), Mn (1.0–42 980), Zn (2.65–33 000) mg/kg, Ca (0.0020–39.0) %, Na (0.010–30.0) %, K (0.0032–20.0) %, Mg (0.0050–41.0) %, P (0.0030–22.4) %. AB 531 — feeds and feed components: Ca, Na, Mg, K, P (from 50 mg/kg), Fe, Mn, Zn, Cu (from 1–5 mg/kg), Cd (75–300) µg/kg, Pb (334–1800) µg/kg, Co (100–14 100) µg/kg, Mo (300–3000) µg/kg; selenium (0.068–176) mg/kg by HG-ICP-OES with hydride generation; selenium premixes — selenium (0.1–5.0) g/100 g. Technique: ICP-OES at all.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. At the elements: the title and scope cover 11 elements, and Mo, Pb, Cd and As only after in-house validation (1) — selenium (AB 531) is named neither in the scope nor in the principle, and hydride generation is not described. At concentrations: the method is not for low concentrations, the quantification limit is normally 1 mg/kg (1) — the lower limits for cadmium, lead, cobalt and molybdenum at AB 531 (75–334 µg/kg) lie below it. At potassium and sulphur: HORRAT > 2, so rather screening (1). At comparisons: results may be higher than with EN 15510 (1, Note 2). At the sample: at most 0.5 g for digestion — homogeneity is decisive; minerals with crystalline water are not ground (8). At sodium: avoid glass at low concentrations (6, note). At calibration: matrix matching; standard addition without a non-linear function (9.3).

WHAT WE DO NOT GIVE. We did not read the rest of the calculation, the precision data (Annex A) or the notes in Annex B. We do not give required or permitted element contents in feed.

Method principle

About 0.5 g of homogeneous, ground feed is digested with nitric acid (in microwave digestion also with hydrogen peroxide) in a closed pressure vessel; the diluted solution is introduced into the ICP-AES plasma and the emission measured at the lines in Table 1, with background correction. Concentrations are calculated from matrix-matched external calibration or by standard addition, in at least two replicates.

Applications

• Ca, Na, P, Mg, K, S, Fe, Zn, Cu, Mn and Co in complete and complementary feeds, premixes, feed materials and additives (1)
• Mo, Pb, Cd, As — after laboratory validation; products with high mineral content — with an accuracy check (1)
• Feeds, feed components and premixes — major and trace elements, at AB 531 also Cd, Pb, Co, Mo and selenium — items in the accreditation scopes of 3 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN 15621:2017-09

Title (PL)

Pasze: Metody pobierania próbek i analiz — Oznaczanie wapnia, sodu, fosforu, magnezu, potasu, siarki, żelaza, cynku, miedzi, manganu i kobaltu po mineralizacji ciśnieniowej metodą ICP-AES

Title (EN)

Animal feeding stuffs: Methods of sampling and analysis — Determination of calcium, sodium, phosphorus, magnesium, potassium, sulphur, iron, zinc, copper, manganese and cobalt after pressure digestion by ICP-AES

Step-by-step procedure

1. Sample

   EN ISO 6498; ≤ 0.5 mm, homogeneous; liquid feeds pre-dried or freeze-dried; minerals with crystalline water not ground (8). PN-EN 15621:2017-09 without a withdrawal note (03.10.2026).

2. Digestion

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

3. Calibration

   Matrix-matched external or standard addition (9.3).

4. ICP-AES

   Blank, standards, sample in ascending order; ≥ 2 replicates; rinsing after each measurement (9.4.2).

5. Calculation

   Net signal after background correction; c = (S − a)/b or the standard addition formula (10).

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 — safety-tested apparatus, sample mass according to the manufacturer’s instructions (6.3, 9.1.1)

Frequently asked questions