🧂 Potassium in water and waste water according to PN-ISO 9964-2 — a standard in force, with a separate national sheet for waste water

Physicochemistry PN-ISO 9964-2

Overview

STATUS (state of the PKN card on 23.09.2026). PN-ISO 9964-2:1994 — Polish version. Publication date 30-12-1994, number of pages 7, technical body KT 121 (Water Quality — Chemical Testing — Inorganic Substances), ICS 13.060.50, "Implements: ISO 9964-2:1993 [IDT]". THE CARD CONTAINS NO "WITHDRAWAL DATE" FIELD AND NO "REPLACED BY" ROW — the standard is in force in the PN collection. In the "Additional elements" field the card indicates PN-ISO 9964-2/Ak:1997.

WHAT WE DID NOT CHECK: the status of the ISO document. The PKN card shows what is happening with the national standard, but does not show whether ISO 9964-2:1993 is still current with its publisher. We did not obtain access to the ISO card (the service rejected the requests), and we do not base statements about the status of a document on search engine summaries. This is a gap in this entry — with national standards implementing an ISO document this discrepancy is sometimes significant.

THE NATIONAL SHEET EXTENDS THE STANDARD TO WASTE WATER. PN-ISO 9964-2/Ak:1997 — "Determination of potassium in waste water by atomic absorption spectrometry (National sheet)", publication date 11-12-1997, 2 pages, KT 121. The card of the sheet also contains no "Withdrawal date" field. The national sheet is not a separate method: it is an addition to the standard, extending its application to a matrix that the international standard does not cover.

WHAT LABORATORIES CITE (measurement on the database of scopes, reading of 23.09.2026): 25 entries at 22 laboratories across all forms of notation; 24 entries at 21 laboratories when matching by the BEGINNING of the notation — this is the number the "Laboratories" tab shows. The most frequent notation is "PN-ISO 9964-2:1994" (15 entries). THE SHEET CAN BE SEEN IN THE NOTATIONS: "PN-ISO 9964-2:1994+Ak:1997" (3 entries), "PN-ISO 9964-2:1994 + Ak:1997" (2), "PN-ISO 9964-2/Ak:1997" (1) — altogether six citations indicate the sheet explicitly. Four entries have waste water as the matrix.

A UNIFORM TECHNIQUE. Twenty-three entries declare flame atomic absorption spectrometry (FAAS) — in line with the title of the standard. One entry describes the methodology more broadly ("Stężenie metali" [concentration of metals]), one combines sodium and potassium in one methodology ("Stężenie sodu i potasu" [concentration of sodium and potassium]), which corresponds to the fact that the 9964 series has separate parts for sodium (part 1) and potassium (part 2).

MEASURING RANGES: (0.10 – 200) mg/l, (0.10 – 500) mg/l, (0.100 – 300) mg/l, (0.5 – 50.0) mg/l, (0.5 – 200) mg/l, (1.00 – 25.0) mg/l, (2 – 30) mg/l. The spread of the lower limits is twentyfold, of the upper — twentyfold.

POTASSIUM HAS NO PARAMETRIC VALUE IN DRINKING WATER — AND THIS IS THE MOST IMPORTANT POINT HERE FOR THE READER OF THE RESULT. In the regulation of the Minister of Health of 22 May 2026 on the quality of water intended for human consumption (Journal of Laws 2026 item 748, in force since 24 June 2026), potassium does NOT appear as a chemical or indicator parameter; the word "potas" [potassium] appears in this act only with the isotope K-40 in the part on radioactivity. For SODIUM — determined by part 1 of the same series — the parametric value is 200 mg/l, and the permissible measurement uncertainty is 15 % of the parametric value. The result of a potassium determination in drinking water is therefore not compared with any limit value from this regulation; it serves other purposes — the ionic balance, the assessment of mineral waters, the control of waste water and of fertilised waters.

WHAT WE DO NOT GIVE. We did not have the text of the standard. We DO NOT GIVE the way of preparing the sample, the ionisation buffer, the wavelength of the analytical line of potassium, the range of the calibration curve or the procedure for saline matrices. A separate entry of the Knowledge Base describes part 1 of this series (sodium) — its content comes from the text of that standard and WE DO NOT TRANSFER it here: these are two different documents, and the details of execution differ at least in the analytical line.

Method principle

The water sample is aspirated into the flame of an atomic absorption spectrometer and the light absorption characteristic of potassium is measured, with the concentration read from a calibration curve. The title of the standard indicates atomic absorption spectrometry, and the accreditation scopes specify further: flame atomisation (FAAS). WE DO NOT DESCRIBE THE DETAILS — the ionisation buffer, the analytical line, the dilutions: we did not have the text of the standard.

Applications

• Determination of potassium in water, including water intended for human consumption
• Determination of potassium in WASTE WATER — on the basis of the national sheet PN-ISO 9964-2/Ak:1997
• Ionic balance of water and assessment of mineral waters, where potassium is a described rather than a limited component
• Reading an accreditation scope in which a standard with a national sheet stands next to potassium

Key parameters

Standard

Standard number

PN-ISO 9964-2:1994 (wersja polska; wprowadza ISO 9964-2:1993 [IDT]) wraz z arkuszem krajowym PN-ISO 9964-2/Ak:1997

Title (PL)

Jakość wody — Oznaczanie sodu i potasu — Oznaczanie potasu metodą absorpcyjnej spektrometrii atomowej

Title (EN)

Water quality — Determination of sodium and potassium — Part 2: Determination of potassium by atomic absorption spectrometry

Step-by-step procedure

1. Checking whether the national sheet is needed

   The standard concerns water quality. If the matrix is WASTE WATER, the national sheet PN-ISO 9964-2/Ak:1997 applies — and it should then be cited next to the standard, as six entries in the accreditation scopes do.

2. Preparing the sample

   Prepare the sample according to the laboratory's procedure. We do not give the details from the standard — we did not have its text.

3. Preparing the calibration curve

   Prepare standard solutions covering the declared range. Treat standards and samples in the same way, in particular as regards the additive suppressing ionisation.

4. Measurement by FAAS

   Aspirate the sample into the flame and measure the absorbance characteristic of potassium. Read results outside the range of the curve only after diluting the sample.

5. Checking what the result is to be used for

   For water intended for human consumption the regulation does not set a parametric value for potassium — the result is not compared with a limit value from this act. If the client expects an assessment of conformity, it must be established with which document the result is to be compared.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The regulation on the quality of drinking water does not set a parametric value for potassium — a report on a potassium determination is not an assessment of conformity with this act, although it looks the same as reports for limited parameters
• Sodium and potassium are TWO DIFFERENT parts of the 9964 series — a citation of "PN-ISO 9964" without the part number does not say which element the laboratory determines
• The national sheet extends the standard to waste water; a test of waste water carried out citing the standard alone, without the sheet, is based on a document that does not cover this matrix
• We did not check the status of the document ISO 9964-2:1993 with its publisher — the PKN card speaks only of the national standard; when citing it in a procedure it is worth checking this at the source
• The laboratories' ranges start at 0.10 to 2 mg/l — with waters of low potassium content, the choice of laboratory decides whether the result will be a number or the entry "below the limit of quantification"

Frequently asked questions