☣️ Chromium(VI) in Water
In short
Photometric determination of chromium(VI) in drinking water in the range from 2 µg/l to 50 µg/l (higher concentrations after dilution) and in weakly polluted ground and surface waters without interfering reducing agents. The test is performed according to PN-EN ISO 18412:2007; Range: 2–50 µg/l of chromium(VI); higher concentrations after dilution of the sample (scope of the standard). The procedure comprises 3 steps; it is used for: Drinking water — chromium(VI) from 2 µg/l to 50 µg/l (scope of the standard), Weakly polluted ground and surface waters without interfering reducing agents (scope of the standard), Monitoring of surface water and groundwater — indicator 3.6.5 “Hexavalent chromium” (Journal of Laws 2021, item 1576, Annex 8).
At a glance
- Standard: PN-EN ISO 18412:2007
- Category: Physicochemistry
- Procedure steps: 3
- Range: 2–50 µg/l of chromium(VI); higher concentrations after dilution of the sample (scope of the standard)
- Matrices: drinking water; weakly polluted ground and surface waters without reducing agents; not waste water (PKN catalogue card)
- Estuarine water and seawater: not tested — validation by the user (scope of ISO 18412)
Overview
STATUS (as of 29.10.2026). PN-EN ISO 18412:2007 — Polish version, published 06.06.2007, implements EN ISO 18412:2006 and ISO 18412:2005 [IDT]; it replaced PN-EN ISO 18412:2006 (English version). The standard was WITHDRAWN on 07.04.2026 — replaced by PN-EN ISO 18724:2026-04 “Water quality — Determination of dissolved chromium(VI) in water — Photometric method” (English version; implements EN ISO 18724:2025 and ISO 18724:2025 [IDT]), which also replaced PN-EN ISO 23913:2009. In ISO, standard 18412:2005 was withdrawn on 01.10.2025; ISO 18724:2025 (first edition, 01.10.2025) replaced ISO 18412:2005, ISO 11083:1994 and ISO 23913:2006.
SCOPE OF PN-EN ISO 18412 (PKN catalogue card, ISO abstract). Determination of chromium(VI) in drinking water in the concentration range from 2 µg/l to 50 µg/l; higher concentrations — after dilution of the sample before analysis. The method can also be applied to weakly polluted ground and surface waters, provided the matrix does not contain interfering reducing agents; it does not cover the testing of waste water. The method was not used for estuarine water and seawater — the user is responsible for its validation for these matrices. The standard has the clauses: scope, normative references, interferences, principle, reagents, apparatus, sampling and sample pretreatment, procedure, evaluation, expression of results, test report and the informative Annex A with precision data.
NEW STANDARD — PN-EN ISO 18724:2026-04 (PKN catalogue card). Photometric determination of dissolved chromium(VI) in water by a manual method (e.g. manual photometry), an automated static method (e.g. a discrete analyser) or automated dynamic techniques — flow injection analysis (FIA), continuous flow analysis (CFA) or ion chromatography with post-column reaction (IC-PCR); after appropriate validation also other matrices, e.g. landfill leachates and raw waste water.
LEGAL REQUIREMENTS. Drinking water: chromium 25 µg/l, and until 12.01.2036 50 µg/l (Journal of Laws 2026, item 748, Annex 1 Part B item 15) — the value applies to chromium, not to chromium(VI) alone; measurement uncertainty 30 % (Annex 4 Part B item 20). Waste water: the reference methodologies for hexavalent chromium are PN-C-04604-8 (photocolorimetry) and PN-EN ISO 10304-3 (ion chromatography) — PN-EN ISO 18412 is not listed there (Journal of Laws 2019, item 1311, Annex 12 item 19). Monitoring of surface water and groundwater: PN-EN ISO 18412 is the spectrophotometric methodology for indicator 3.6.5 “Hexavalent chromium”, alongside PN-EN ISO 10304-3 (ion chromatography) and PN-EN ISO 23913 (flow analysis) (Journal of Laws 2021, item 1576, Annex 8).
WHAT WE DO NOT GIVE HERE. Only the forewords and the table of contents of the standard are publicly available. We do not give the reagents, wavelength, reaction conditions, sample preservation, calibration or precision data of ISO 18412. For orientation, we describe the principle of the reaction according to EPA Method 7196A — a different document, marked in the text.
Method principle
The determination is photometric (title and scope of the standard); the principle of the reaction of ISO 18412 is not covered by the publicly available text.
In EPA Method 7196A (second source, a different document), chromium(VI) is determined colorimetrically by reaction with diphenylcarbazide in acid solution: a red-violet product is formed, and its absorbance is measured photometrically at 540 nm.
Applications
- Drinking water — chromium(VI) from 2 µg/l to 50 µg/l (scope of the standard)
- Weakly polluted ground and surface waters without interfering reducing agents (scope of the standard)
- Monitoring of surface water and groundwater — indicator 3.6.5 “Hexavalent chromium” (Journal of Laws 2021, item 1576, Annex 8)
- New determinations — according to PN-EN ISO 18724:2026-04, which also covers flow techniques and IC-PCR
Key parameters
| Parameter | Value |
|---|---|
| Range | 2–50 µg/l of chromium(VI); higher concentrations after dilution of the sample (scope of the standard) |
| Matrices | drinking water; weakly polluted ground and surface waters without reducing agents; not waste water (PKN catalogue card) |
| Estuarine water and seawater | not tested — validation by the user (scope of ISO 18412) |
| Status | withdrawn on 07.04.2026; successor — PN-EN ISO 18724:2026-04 (English version) |
| Parametric value (drinking water) | chromium 25 µg/l, until 12.01.2036 50 µg/l (Journal of Laws 2026, item 748, Annex 1 Part B item 15) |
Standard
- Standard number
- PN-EN ISO 18412:2007
- Title (PL)
- Jakość wody — Oznaczanie chromu(VI) — Metoda fotometryczna dla wód słabo zanieczyszczonych
- Title (EN)
- Water quality — Determination of chromium(VI) — Photometric method for weakly contaminated water
Step-by-step procedure
-
Assessment of the sample
Check that the sample is within the scope of the standard: drinking water or weakly polluted ground or surface water without interfering reducing agents; estuarine water and seawater — only after own validation (scope of the standard).
-
Dilution
Dilute samples with a chromium(VI) concentration above 50 µg/l before analysis (scope of the standard).
-
Determination
Sampling and sample pretreatment, procedure, evaluation and expression of results — according to clauses 7–10 of the standard, outside the publicly available text.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Apparatus | the requirements are given in clause 6 of the standard — outside the publicly available text; the determination is photometric (title of the standard) | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Reagents | — | composition and preparation are given in clause 5 of the standard — outside the publicly available text |
Health and safety (OHS)
- Chromium(VI) compounds and reagents are handled according to the safety data sheets
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 18412:2007 — “Water quality — Determination of chromium(VI) — Photometric method for weakly contaminated water”.
How does this method work?
The determination is photometric (title and scope of the standard); the principle of the reaction of ISO 18412 is not covered by the publicly available text. In EPA Method 7196A (second source, a different document), chromium(VI) is determined colorimetrically by reaction with diphenylcarbazide in acid solution: a red-violet product is formed, and its absorbance is measured photometrically at 540 nm.
What is the measuring range and accuracy?
Range: 2–50 µg/l of chromium(VI); higher concentrations after dilution of the sample (scope of the standard); Matrices: drinking water; weakly polluted ground and surface waters without reducing agents; not waste water (PKN catalogue card); Estuarine water and seawater: not tested — validation by the user (scope of ISO 18412); Status: withdrawn on 07.04.2026; successor — PN-EN ISO 18724:2026-04 (English version).
How long does the test take?
The procedure comprises 3 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Apparatus.
Where is this test used?
Drinking water — chromium(VI) from 2 µg/l to 50 µg/l (scope of the standard); Weakly polluted ground and surface waters without interfering reducing agents (scope of the standard); Monitoring of surface water and groundwater — indicator 3.6.5 “Hexavalent chromium” (Journal of Laws 2021, item 1576, Annex 8); New determinations — according to PN-EN ISO 18724:2026-04, which also covers flow techniques and IC-PCR.
What safety precautions apply?
Chromium(VI) compounds and reagents are handled according to the safety data sheets.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 18412.