🧪 Cadmium in water and wastewater — flame and electrothermal AAS

Physicochemistry PN-EN ISO 5961

Overview

WHAT THIS STANDARD DESCRIBES. The scope from the PKN catalogue card, in full: "Podano dwie metody oznaczania kadmu: z zastosowaniem absorpcyjnej spektrometrii atomowej (AAS) w płomieniu powietrze-acetylen (zasysanie zakwaszonej próbki do płomienia i pomiar stężenia kadmu przy długości fali 228,8 nm) oraz AAS z elektrotermiczną atomizacją (wprowadzenie zakwaszonej próbki do elektrycznie ogrzewanej grafitowej kuwety spektrometru absorpcji atomowej z elektrotermiczną atomizacją i pomiar przy długości fali 228,8 nm)" [Two methods for the determination of cadmium are given: atomic absorption spectrometry (AAS) in an air–acetylene flame (aspiration of the acidified sample into the flame and measurement of the cadmium concentration at a wavelength of 228.8 nm) and AAS with electrothermal atomisation (introduction of the acidified sample into the electrically heated graphite furnace of an atomic absorption spectrometer with electrothermal atomisation and measurement at a wavelength of 228.8 nm)]. The Polish edition was published on 15 March 2001, has 13 pages and is maintained by KT 121 Water Quality — Chemical Testing — Inorganic Substances, ICS 13.060.50; it implements EN ISO 5961:1995 and ISO 5961:1994. The card gives no withdrawal date (state of the card on 23.09.2026).

ONE STANDARD, TWO TECHNIQUES. The regulation of the Minister of Maritime Economy and Inland Navigation of 12 July 2019 (Journal of Laws 2019 item 1311) lists in Annex No. 12, under item 35 "Kadm" [cadmium], five methodologies: atomic absorption spectroscopy with flameless atomisation (PN-EN ISO 15586), AAS with flame atomisation (PN-ISO 8288), AAS with flame AND flameless atomisation (PN-EN ISO 5961), inductively coupled plasma atomic emission spectrometry (PN-EN ISO 11885) and inductively coupled plasma mass spectrometry (PN-EN ISO 17294-2). The third item of this list is not a third technique, but a standard that describes the first two. For the whole item — the table cell spans all five rows — the act gives the requirement: limit of detection 0.1 of the permissible concentration at the sampling point, accuracy and precision ± 30% at a concentration equal to the limit of detection. Explanatory note 3 to the annex defines the limit of detection as the concentration corresponding to the signal calculated from the blank value increased by three times the standard deviation, and explanatory note 4 calls the method of PN-EN ISO 11885 "szczególnie zalecaną w sytuacjach oznaczania w jednej próbce większej liczby pierwiastków" [particularly recommended where a larger number of elements are determined in one sample], listing cadmium among them.

WHAT THE MEASUREMENT SHOWS. Copy of the accreditation scopes, reading of 23.09.2026. All notations of the number in the reference-document field (neither a digit nor a letter may stand before the number, and no digit after it): PN-EN ISO 11885 — 86 laboratories and 261 entries; PN-ISO 8288 — 86 and 156; PN-EN ISO 15586 — 66 and 143; PN-EN ISO 17294-2 — 50 and 104; PN-EN ISO 5961 — 2 and 2. We count the entries concerning cadmium in two ways. When cadmium stands in the TEST NAME: 93 laboratories, 189 entries; with them PN-EN ISO 15586 — 15 laboratories, PN-EN ISO 11885 — 8, PN-ISO 8288 — 7, PN-EN ISO 17294-2 — 7, PN-EN ISO 5961 — 2. When cadmium stands in the test name OR in the list of parameters, also in group tests of the kind "Stężenie metali" [metal concentration]: 181 laboratories, 505 entries; with them PN-EN ISO 15586 and PN-EN ISO 11885 — 48 laboratories each, PN-EN ISO 17294-2 — 35, PN-ISO 8288 — 30, PN-EN ISO 5961 — 2. Under the wider measure this standard is thus cited by roughly one laboratory in ninety of those determining cadmium.

TWO NOTATIONS, ONE OF THEM DISTORTED. One entry of this standard has the notation "PN-EN ISO 5961:2001" in the database, the other — "PN- EN ISO 5961:2001 rozdział 2" [rozdział = chapter], with a space after the hyphen. The "Laboratories" tab searches for notations beginning with "PN-EN ISO 5961", so it shows only the first. With two entries, one distorted notation is half of the reach of the standard; with a standard cited by two hundred laboratories it would be half a per cent.

BEWARE OF SIMILAR NUMBERS. The string "5961" searched for without boundaries hits 41 entries at 18 laboratories, but only two of them concern this standard. The others are above all "PN-EN 15961:2017-02" (36 times), and also "PN-EN 15961:2017", "PN-A-75961:2002", "ASTM D5961/D5961M" and the field "PN-EN 15960:2011 P N-EN 15961:2017-02". In the numbers 15961 and 75961 the string 5961 is the end of a longer number, and in "ASTM D5961" it stands after the letter of a designation from another system. Correct counting therefore requires a boundary on both sides of the number — and cutting off both a digit and a letter on the left. Without this the number of laboratories comes out nine times too large.

WHAT WE DO NOT GIVE. We did not have the text of the standard — PKN makes it available for a fee (13 pages). The card describes both variants: the air–acetylene flame and the electrically heated graphite furnace, measurement at 228.8 nm, an acidified sample. We do not give the limits of quantification of the variants, the temperature programme of the furnace, the modifiers, the background correction or the sample preparation.

Method principle

According to the card of the standard: two variants of atomic absorption spectrometry. In the first, the acidified sample is aspirated into an air–acetylene flame; in the second, the acidified sample is introduced into the electrically heated graphite furnace of a spectrometer with electrothermal atomisation. In both, cadmium is measured at a wavelength of 228.8 nm. WE DO NOT GIVE the limits of quantification of the two variants, the atomisation conditions or the sample preparation — we did not have the text of the standard.

Applications

• Water — a standard of the "Water quality" group (title)
• Testing of wastewater for the purposes of Journal of Laws 2019 item 1311 — one of the five methodologies listed for cadmium (Annex No. 12, item 35); the limit-of-detection requirement of this item applies

Key parameters

Standard

Standard number

PN-EN ISO 5961:2001

Title (PL)

Jakość wody — Oznaczanie kadmu metodą absorpcyjnej spektrometrii atomowej

Title (EN)

Water quality — Determination of cadmium by atomic absorption spectrometry

Step-by-step procedure

1. Choice of variant

   The standard describes two variants of atomisation. When testing wastewater, the regulation requires for cadmium a limit of detection of 0.1 of the permissible concentration at the sampling point — the chosen variant must ensure it.

2. Sample preparation

   The sample is acidified (card). WE DO NOT GIVE the acid, any digestion or filtration.

3. Measurement

   At 228.8 nm in both variants (card). WE DO NOT GIVE the operating conditions — we did not have the text of the standard.

4. Entry in the report

   State the variant — flame or electrothermal: the standard contains both, and its number alone does not say which one was used to determine cadmium.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Acetylene — the flammable flame gas in the flame variant (card); rules for working with cylinders and the instrument according to the manufacturer's instructions and the safety data sheets
• This entry does not quote the hazards associated with cadmium and the reagents — the safety data sheets of the standards and reagents used in the laboratory apply

Frequently asked questions