🔬 Heavy metals in water — AAS

Physicochemistry PN-ISO 8288

Overview

STATUS (as of 29.10.2026). PN-ISO 8288:2002 — Polish version, published 29.03.2002, implements ISO 8288:1986 [IDT]; it replaced PN-C-04570-01:1992 and PN-C-04570-04:1992. The standard is current — no withdrawal note. ISO 8288:1986 (first edition) is published in the ISO catalogue, with no newer edition.

SCOPE (clauses 1–2). Three methods for determining cobalt, nickel, copper, zinc, cadmium and lead in water: method A — direct determination in the flame, method B — after chelation with ammonium 1-pyrrolidinedithiocarbamate (APDC) and extraction with methyl isobutyl ketone (MIBK), method C — after chelation (HMA-HMDC) and extraction with a DIPK-xylene mixture. Method A is suitable for relatively high concentrations without interferences; for complex samples or samples of unknown nature and for samples with high dissolved solids (brines, brackish waters) method A is not applicable — method B or C is chosen. Ranges given in the standard (they depend on the instrument): method A — cobalt and nickel 0.1–10 mg/l, copper 0.05–6 mg/l, zinc 0.05–2 mg/l, cadmium 0.02–2 mg/l, lead 0.2–10 mg/l; method B — cobalt, nickel and copper 1–200 µg/l, zinc and cadmium 0.5–50 µg/l, lead 5–200 µg/l; method C — cobalt, nickel and copper 0.5–100 µg/l, zinc and cadmium 0.2–50 µg/l, lead 2–200 µg/l (at a test portion to extraction solution ratio of 20 : 1). Concentrations above the upper limits — after dilution of the sample. For total metals the sample has to be digested first (examples in Annex A); methods B and C are not applicable when the COD of the sample exceeds 500 mg/l.

INTERFERENCES AND CHECKS (7.4–7.5). Non-specific absorption is compensated by the spectrometer's continuous background correction; without it, the non-specific absorbance is measured on a line not more than 1 nm from the line of the element (a line of the lamp gas, a zirconium or a deuterium lamp — Table 5) and subtracted from the total absorbance. The matrix effect is checked by the method of standard additions; if it is present, method A is not applicable — the determination is repeated by method B or C, or the results of the standard addition method are used.

LEGAL REQUIREMENTS. Water intended for human consumption (Regulation of the Minister of Health of 22 May 2026, Journal of Laws 2026, item 748, Annex 1 Part B): cadmium 5.0 µg/l (item 19), copper 2.0 mg/l (item 21), nickel 20 µg/l (item 23), lead 5 µg/l (item 24 — until 12.01.2036 the value is 10 µg/l); cobalt and zinc are not listed. The method must measure a concentration equal to the parametric value with a limit of quantification not greater than 30 % of that value and an uncertainty of up to 25 % (cadmium, copper, nickel) or 30 % (lead) of the parametric value (Annex 4 Part B) — for cadmium, nickel and lead these concentrations lie below the range of method A. Waste water: PN-ISO 8288 is one of the reference methods (flame atomic absorption spectroscopy) for zinc, cadmium, cobalt, copper, nickel and lead (Journal of Laws 2019, item 1311, Annex 12, items 22, 35, 37, 38, 40, 43). Monitoring of surface and ground waters: method for zinc and copper (Journal of Laws 2021, item 1576, Annex 8, indicators 3.6.7 and 3.6.8).

WHAT WE DO NOT GIVE HERE. The publicly available text of the standard covers method A in full and the beginning of method B (up to 14.3). The rest of method B, method C, the digestion examples (Annex A) and precision data are described only to the extent of the sentences above.

Method principle

Method A (clause 3): a portion of the acidified filtrate of the sample (or of the diluted sample) is aspirated into the flame of an atomic absorption spectrometer. The concentration of each element is determined directly from the specific absorbance — with a spectrometer with continuous background correction or after subtracting the non-specific absorbance. The radiation sources are hollow cathode lamps or electrodeless discharge lamps; the flame is acetylene–air, oxidizing for nickel and copper.

Wavelengths according to Table 4 of the standard: cobalt 240.7 nm, nickel 232.0 nm, copper 324.7 nm, zinc 213.8 nm, cadmium 228.8 nm, lead 283.3 nm or 217.0 nm.

Method B (clause 10): the metals form complexes with APDC, which are extracted with MIBK at pH about 2.5, and the metals are determined in the organic phase in the flame. Method C uses chelation with HMA-HMDC and extraction with a DIPK-xylene mixture; phase separation is faster and the chelates — especially that of cadmium — are more stable in the organic phase (clause 2).

Applications

• Water intended for human consumption — cadmium, copper, nickel and lead (Journal of Laws 2026, item 748, Annex 1 Part B)
• Waste water — one of the reference methods for zinc, cadmium, cobalt, copper, nickel and lead (Journal of Laws 2019, item 1311, Annex 12)
• Monitoring of surface and ground waters — zinc and copper (Journal of Laws 2021, item 1576, Annex 8)
• Brines, brackish waters and samples of unknown nature — methods B and C with extraction (clause 2)

Key parameters

Standard

Standard number

PN-ISO 8288:2002 (ISO 8288:1986)

Title (PL)

Jakość wody — Oznaczanie kobaltu, niklu, miedzi, cynku, kadmu i ołowiu — Metody atomowej spektrometrii absorpcyjnej z atomizacją w płomieniu

Title (EN)

Water quality — Determination of cobalt, nickel, copper, zinc, cadmium and lead — Flame atomic absorption spectrometric methods

Step-by-step procedure

1. Sampling and preservation

   Total metals: immediately after collection acidify with 1.4 g/ml nitric acid to pH 1–2 (usually 2 ml of acid per litre of sample is sufficient); record the amount of acid and add the same amount to the blank. Dissolved metals: filter the sample as soon as possible through a 0.45 µm membrane filter and acidify the filtrate immediately to pH 1–2 (6.2).

2. Test portion

   Place in a 100 ml volumetric flask an amount of the acidified sample containing 0.2–1 mg of metal (upper limits — Table 1) and make up with water (7.1).

3. Blank test

   In parallel, by the same procedure and with the same quantities of reagents, with water instead of the test portion (7.2).

4. Calibration solutions

   Before each batch of determinations prepare from the standard solutions at least four calibration solutions covering the range of concentrations to be determined, diluting them with 0.03 mol/l nitric acid (7.3).

5. Setting up the spectrometer

   According to the manufacturer's instructions and Table 4, aspirating a calibration solution of the metal; optimize the aspiration rate, the nature of the flame and the position of the beam in the flame; set zero with water (7.4).

6. Calibration

   Aspirate the calibration solutions and — as the zero member — the blank; plot absorbance against metal concentration in mg/l. Checking the graph is advisable, e.g. by measuring a calibration solution every 5 samples (7.4).

7. Measurement

   Aspirate the test portion into the flame and measure the absorbance; after each measurement aspirate 0.03 mol/l nitric acid to rinse the nebulizer. Without automatic background correction measure the non-specific absorbance (Table 5) and subtract it; flame conditions and lamp energy unchanged during both measurements (7.4).

8. Matrix effect check

   By the method of standard additions; in the case of a matrix effect repeat the determination by method B or C or use the results of the standard addition method (7.5).

9. Calculation

   Metal concentration in the sample, mg/l = (ρt − ρb) × 100/V, where ρt and ρb are the concentrations read from the graph for the test portion and the blank, V is the volume of acidified sample taken, ml (clause 8).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Handle nitric acid, MIBK, APDC and metal solutions (cadmium, lead, nickel, cobalt) according to the safety data sheets
• Acetylene–air flame — gas installation and extraction above the burner according to the spectrometer manufacturer's instructions

Frequently asked questions