🌿 Determination of cadmium content in solid mineral fertilizers and rock phosphates — 1–12.5 g of sample ground to 0.5 mm is boiled gently for 30 min with nitric acid (1 + 1), the extract diluted to 250 ml and filtered, and cadmium measured by flame atomic absorption spectrometry (Method A) or ICP-OES (Method B), calibrated by the method of three standard additions; contents above 1 mg/kg, PN-EN 14888

Environment PN-EN 14888

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN 14888:2006 (Polish version), in full (our translation): “Two methods are described for the determination of cadmium content in soil, mineral fertilizers and rock phosphates after extraction with nitric acid: — Method A — determination of cadmium content using flame atomic absorption spectrometry (flame AAS), — Method B — determination of cadmium content by inductively coupled plasma optical emission spectrometry (ICP-OES)” (the Polish card contains a typing error). The words “in soil” are not in Clause 1 of the text of EN 14888:2005 — the text speaks of solid mineral fertilizers and rock phosphates. We read the text of the standard in the sample of SIST EN 14888:2005 (the text of EN 14888:2005 without changes) from the title page through the contents, foreword, introduction and Clauses 1–7 up to and including 8.4.2 of Clause 8. Outside the sample remain 8.4.3 (measurement by ICP-OES), Clause 9 (calculation and expression of results), 10 (precision), 11 (test report) and Annexes A (results of inter-laboratory tests) and B (notes on the detection techniques, interferences and quantification).

ACCORDING TO THE TEXT OF EN 14888:2005 (Clauses 1–7, 8.1–8.4.2). The standard was prepared by CEN/TC 260 “Fertilizers and liming materials” (secretariat DIN) under a mandate of the European Commission, as a means of conforming to the essential requirements of Regulation (EC) No 2003/2003 relating to fertilizers. Introduction: flame AAS and ICP-OES are widely used for cadmium, so the standard describes both (Method A and B) with most of the reagents and procedure in common. Scope (1): two methods for cadmium after extraction with nitric acid in solid mineral fertilizers and rock phosphates; not applicable to organic and organo-mineral fertilizers; applicable to cadmium contents greater than 1 mg/kg. Definitions (3): limit of detection — numerically three standard deviations of the mean of blank determinations (n > 10); limit of quantification — numerically ten such standard deviations, if accuracy and precision are constant near the limit of detection. Principle (4): cadmium is extracted from the fertilizer with nitric acid, and its concentration is measured by flame AAS (Method A) or ICP-OES (Method B); both techniques are relative, and concentrations are determined by the standard addition method. Reagents (5): reagents of recognized analytical grade and water of grade 2 according to EN ISO 3696:1995; stock solutions are replaced after one year at the latest, the standard solution at least monthly; nitric acid 65 % (approx. 1.42 g/ml), diluted approx. 7 mol/l (1 + 1), approx. 4.3 mol/l (1 + 3) and 2 % (V/V); cadmium stock solution 1000 mg/l — approx. 1.000 g of metallic cadmium (purity at least 99.5 %, free of oxide layers) in 40 ml of acid (1 + 3), 100 ml of water, boiling to expel nitrous fumes, to 1000 ml — or a commercial solution; standard solutions 50 mg/l and 1 mg/l in 2 % nitric acid. Warning: cadmium is highly toxic. Apparatus (6): analytical balance accurate to 0.1 mg, laboratory grinder to 0.5 mm or less, hot plate with temperature control, flame AAS with cadmium source, background correction and air–acetylene burner; ICP-OES with at least radially viewed plasma — axially only if it is shown that results are statistically equal to radial ones — with background correction and working conditions optimized according to the manufacturer. Sampling and preparation (7): sampling according to EN 1482; the laboratory sample is ground to 0.5 mm or less without appreciable heating, as quickly as possible so as not to lose or gain constituents (water, ammonia), and mixed thoroughly; blended fertilizers that segregate are ground to 0.2 mm or less, and products that decompose on heating — preferably in a mortar. Extraction (8.1.1, Table 1): test portion to the nearest 0.1 mg depending on the expected (declared) cadmium content — at 1–5 mg/kg 12.5 g of sample and 125 ml of acid (1 + 1), at 5–15 mg/kg 5 g and 50 ml, at 15–30 mg/kg 2.5 g and 25 ml, at 30–100 mg/kg 1 g and 10 ml; always to 250 ml, giving in the extract respectively 0.05–0.25, 0.10–0.30, 0.15–0.30 and 0.12–0.40 mg/l cadmium; the sample is moistened with water, acid added, covered with a watch glass and boiled gently for 30 min, adding water to maintain the volume; after cooling transferred to a volumetric flask, made up with water, mixed and filtered through a dry filter, discarding the first portion of filtrate. Masses and volumes were chosen so that concentrations exceed the typical limits of quantification of both techniques, lie within their linear range, and the salt content is not too high. Test solution (8.1.2): 50.00 ml of filtrate to a 100 ml flask, made up with 2 % nitric acid. Blank (8.2): in parallel, with reagents only. Calibration (8.3): by standard addition — to three portions of 50.00 ml of filtrate 2.00 ml, 5.00 ml and 10.00 ml of cadmium solution 1 mg/l are added and made up to 100 ml with 2 % nitric acid; an external calibration curve may be used instead of standard addition only if statistical equality of results is demonstrated, and then with matrix matching of the calibration solutions. Measurement (8.4): for each instrument selectivity, limits of detection and quantification, precision, linear range and interference are established separately; in Method A the blank, the test solution and the additions in ascending order are aspirated into the flame, each read at least twice and averaged if the values are within an accepted range; after each measurement the blank is aspirated and zero readjusted if necessary.

STATUS (catalogue cards as of 03.10.2026). The card of PN-EN 14888:2006 (Polish version, published 07-12-2006, 20 pages, price group K) has no “Withdrawn” header: Chemistry Sector, KT 156 Fertilizers, ICS 65.080, “Introduces: EN 14888:2005 [IDT]”, “Supersedes: PN-EN 14888:2006 — English version”. The card of PN-EN 14888:2006 (English version, published 15-03-2006, 22 pages) — “Withdrawn” 07-12-2006, “Replaced by: PN-EN 14888:2006 — Polish version”, and itself superseded “PN-C-87007-10:1993 — Polish version”. Both versions introduce the same EN 14888:2005 — the change concerned the language, not the content. The PKN search (term “PN-EN 14888”, 03.10.2026) shows no other editions of this standard (the remaining hits are PN-ISO/IEC 14888 on digital signatures). In the iTeh catalogue (read 03.10.2026) the Slovenian adoption SIST EN 14888:2005 has the status “Published”.

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 14888 appears in 6 records at 6 laboratories: AB 277, AB 312, AB 333, AB 339, AB 930, AB 1186. In the current scopes on the PCA website (read 03.10.2026, issues from 24.06.2025 to 22.07.2026) all give “PN-EN 14888:2006”, AB 339 with the note “method A”. The “Laboratories” tab (“PN-EN 14888”) shows the same 6 laboratories; checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (PCA items). All six — “Cadmium content”, technique: flame atomic absorption spectrometry (FAAS), i.e. Method A; Method B (ICP-OES) with this reference does not appear in the scopes. Objects: agricultural limes (AB 312, AB 1186), agricultural lime — calcium fertilizer (AB 333), agricultural limes and liming materials (AB 339), calcium fertilizers and liming materials (AB 930), mineral (inorganic) fertilizers (AB 277). Ranges: (1.0–75.0) mg/kg (AB 312), (0.50–75.0) mg/kg (AB 1186), (0.70–100) mg/kg (AB 333), (1.0–50.0) mg/kg (AB 339), (1.0–20.0) mg/kg (AB 930), (0.25–15.0) mg/kg (AB 277). AB 277 cites the standard jointly with PN-C-87006-15:1996 and PN-C-87070-04:1992+Az1:1997, and AB 339 — with PN-C-87006-15:1996 p. 4.2. The card of PN-C-87006-15:1996 (calcium-magnesium fertilizers — determination of cadmium; three methods: AAS with graphite furnace, flame AAS acetylene–air and voltammetry) has the header “Withdrawn”: withdrawal date 05-08-2022, without a “Replaced by” field. The card of PN-C-87007-10:1993 (calcium fertilizers — determination of cadmium content) — “Withdrawn” 15-03-2006, “Replaced by: PN-EN 14888:2006 — English version” — for cadmium in calcium fertilizers PKN thus indicates precisely this standard as the successor. The card of PN-C-87070-04:1992 (nitrogen and phosphorus fertilizers — determination of cadmium) and its amendment Az1:1997 — “Withdrawn” 30-05-2014, without a “Replaced by” field; both standards cited jointly by AB 277 and AB 339 are thus withdrawn.

WHERE A SEEMINGLY CORRECT RESULT IS EASY. At the object: Clause 1 of the text speaks of solid mineral fertilizers and rock phosphates, and liming materials appear only in the title; all six laboratories test agricultural limes or liming materials with this standard — the text in the part read says nothing more about them. The PKN card adds “soil” to the scope, which the text does not mention. At the lower limit: the standard applies above 1 mg/kg — the ranges of AB 277 (from 0.25 mg/kg), AB 1186 (from 0.50 mg/kg) and AB 333 (from 0.70 mg/kg) start below this limit, so results in that interval are not covered by the scope of the standard. At extraction: the test portion and the amount of acid are chosen from Table 1 according to the EXPECTED content — with too small a portion the concentration in the extract falls below the limit of quantification, with too large a portion the salt content rises; evaporation without adding water changes the extraction conditions (8.1.1). At calibration: an external calibration curve without matrix matching and without demonstrating equality with standard addition does not meet the standard (8.3). At measurement: the standard requires background correction in both techniques (6.5, 6.6), and the notes on interferences are in Annex B, which we did not read; axial viewing of the plasma in ICP-OES requires demonstrating equality of results with radial viewing (6.6). At the result: the standard determines cadmium “after extraction with nitric acid” (1, 4) — the result is the cadmium extracted under its conditions; the text does not speak of total dissolution.

WHAT WE DO NOT GIVE. We did not read 8.4.3, Clauses 9–11 and Annexes A–B, so we do not give the calculation formula, measuring wavelengths, precision data or the content of the test report. We did not read the content of PN-C-87006-15:1996 and PN-C-87070-04:1992 cited jointly by two laboratories. We do not give limit values for cadmium in fertilizers and liming materials, because we did not read the texts of regulations for this entry.

Method principle

Cadmium is extracted from the ground fertilizer by boiling with nitric acid (1 + 1) for 30 minutes; the amount of sample and acid is chosen according to the expected content so that after dilution to 250 ml the concentration lies within the measuring range. In the filtrate, diluted twofold with 2 % nitric acid, cadmium is measured by flame atomic absorption spectrometry with background correction (Method A) or ICP-OES (Method B), calibrated by three standard additions to portions of the same filtrate, which compensates for the matrix effect.

Applications

• Solid mineral fertilizers and rock phosphates — cadmium content above 1 mg/kg; not applicable to organic and organo-mineral fertilizers (Clause 1)
• Agricultural limes and liming materials — the object of testing of all 6 laboratories that have the standard in their PCA accreditation scopes (Method A only, FAAS)

Key parameters

Standard

Standard number

PN-EN 14888:2006

Title (PL)

Nawozy i środki wapnujące — Oznaczanie zawartości kadmu

Title (EN)

Fertilizers and liming materials — Determination of cadmium content

Step-by-step procedure

1. Sample preparation

   Sampling according to EN 1482; grinding to ≤ 0.5 mm without heating (blended fertilizers to ≤ 0.2 mm), mixing. PN-EN 14888:2006 current (PKN catalogue card as of 03.10.2026).

2. Extraction

   Test portion and acid (1 + 1) according to Table 1; moisten with water, add acid, cover, boil gently 30 min, adding water; cool, to 250 ml, filter through a dry filter, discard the first portion.

3. Measuring solutions

   50.00 ml of filtrate to 100 ml with 2 % nitric acid; blank with reagents only; three standard additions: 2.00, 5.00 and 10.00 ml of Cd solution 1 mg/l to 50.00 ml of filtrate, to 100 ml.

4. FAAS measurement (Method A)

   Blank, test solution and additions in ascending order; each at least twice, average; after each measurement blank and zero adjustment. ICP-OES measurement (8.4.3) and calculation (Clause 9) — outside the sample read.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Cadmium is highly toxic — all necessary measures to avoid ingestion (warning in 5.1)
• Boiling with nitric acid releases nitrous fumes — in a fume hood; concentrated acid is corrosive
• Air–acetylene flame — safety rules for flammable gases according to the spectrometer instructions

Frequently asked questions