🔬 Selenium in Water (ICP-OES)

Physicochemistry PN-EN ISO 11885

Overview

STATUS (as of 03.11.2026). PN-EN ISO 11885:2009 — English version (Polish title in the PKN catalogue), published on 23.07.2009, implements EN ISO 11885:2009 and ISO 11885:2007 [IDT]; it replaced PN-EN ISO 11885:2001 (Polish version). The PKN catalogue card has no note of withdrawal. ISO 11885:2007 (second edition) has the stage “confirmed after review” (90.93) in the ISO catalogue. The description agrees with the description of the same standard in the method “Metals in water — ICP-OES”.

SCOPE (clause 1). A method for the determination of dissolved elements, elements bound to particles and their total content in different types of water (e.g. ground, surface, raw, drinking water and waste water) for 35 elements — selenium is one of them; the standard does not cover mercury. Taking interferences into account, the same elements can be determined in digests of water, sewage sludge and sediments (e.g. according to ISO 15587-1 or ISO 15587-2). The method is suitable for waste water with particulate matter below 2 g/l; extension to other matrices requires the user to demonstrate that the additional interferences have been considered and corrected.

PRINCIPLE (clause 4). The method is based on measuring the emission of light by an optical spectroscopic technique. The sample is nebulised and the aerosol produced is transported to the plasma torch, where excitation occurs; the radio-frequency inductively coupled plasma produces characteristic emission spectra, which are dispersed by a grating spectrometer, and the line intensities are monitored by the detector (detectors). The signals are processed and the measurement is controlled by a computer system; variable background contributions in the determination of trace elements are compensated by a suitable background correction technique.

SELENIUM LINE (clause 5, Table 1). Recommended wavelengths, achievable limits of quantification for radial and axial viewing of the plasma and the most important spectral interferences are given in Table 1 of the standard — values from the interlaboratory trial (Annex B); the actual limits depend on the instrument, detector, sample introduction system and matrix. The selenium row is outside the available text of the standard. For comparison: method EPA 200.7 (rev. 4.4, Table 1) gives for selenium the line 196.090 nm and an estimated instrument detection limit of 75 µg/l.

LIMITS OF DETECTION AND QUANTIFICATION (3.10–3.11). The limit of detection is 3 s₀ and the limit of quantification is 3 limits of detection (9 s₀), where s₀ is the standard deviation of the results of at least 3 measurements of a reagent blank solution.

REGULATIONS. Drinking water: the parametric value for selenium is 20 µg/l, and 30 µg/l in regions where geological conditions could lead to high levels of selenium in groundwater (Dz.U. 2026 item 748, Annex 1 part B item 28); the method must have a limit of quantification of no more than 30 % of the parametric value and a measurement uncertainty of no more than 40 % (Annex 4 part B). The regulation applies from 24.06.2026; the previous one (Dz.U. 2017 item 2294) gave 10 µg/l. Waste water: the maximum permissible value for selenium in industrial waste water is 1 mg Se/l (Dz.U. 2019 item 1311, Annex 4 Table II item 34), and the reference methods for selenium are atomic absorption spectrometry with electrothermal atomisation (PN-EN ISO 15586), ICP-OES (PN-EN ISO 11885) and ICP-MS (PN-EN ISO 17294-2) — ICP-OES is particularly recommended when a larger number of elements is determined in one sample (Annex 12 item 51 and explanatory note 4).

WHAT WE DO NOT GIVE HERE. The publicly available text of the standard covers clauses 1–5 (up to the beginning of Table 1, without the selenium row). Interferences (clause 6), reagents (clause 7), apparatus (clause 8), sampling and preservation (clause 9), procedure (clause 10), expression of results (clause 11), special digestion methods (Annex A) and precision data (Annex B) are outside it — which is why we do not give volumes, concentrations of solutions, digestion conditions or the frequency of checks. The hydride generation technique is not part of this standard.

Method principle

Selenium is determined by measuring the intensity of its emission lines in the spectrum of a radio-frequency inductively coupled plasma. The sample is nebulised, the aerosol reaches the plasma torch, and the spectrum is dispersed by a grating spectrometer and measured by the detector (detectors) with background correction. The concentration is determined by calibration with standard solutions; the achievable limit of quantification depends on the selected line and on the viewing of the plasma (radial or axial) according to Table 1 of the standard.

Applications

• Water intended for human consumption — parametric value 20 µg/l, 30 µg/l in regions with geologically high selenium levels in groundwater (Dz.U. 2026 item 748, Annex 1 part B item 28)
• Waste water — one of the three reference methods for selenium (Dz.U. 2019 item 1311, Annex 12 item 51)
• Ground, surface and raw water — dissolved, particulate and total selenium (clause 1)
• Digests of water, sewage sludge and sediments (e.g. ISO 15587-1, ISO 15587-2)

Key parameters

Standard

Standard number

PN-EN ISO 11885:2009

Title (PL)

Jakość wody — Oznaczanie wybranych pierwiastków metodą optycznej spektrometrii emisyjnej z plazmą wzbudzoną indukcyjnie (ICP-OES)

Title (EN)

Water quality — Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES)

Step-by-step procedure

1. Sampling and preservation

   According to ISO 5667-1 and ISO 5667-3 (normative references) and clause 9 of the standard, which is outside the available text.

2. Choice of form

   Dissolved, particulate or total selenium; total content — determination in the unfiltered sample after digestion or the sum of the dissolved and particulate fractions (3.26).

3. Digestion — when needed

   E.g. according to ISO 15587-1 (aqua regia) or ISO 15587-2 (nitric acid); special digestion methods — informative Annex A (outside the available text).

4. Choice of line and instrument set-up

   Choose the selenium line and consider the spectral interferences according to Table 1 of the standard; the viewing mode of the plasma (radial or axial) affects the achievable limit of quantification.

5. Calibration

   Calibration solutions and calibration blank; the calibration is checked with an independently prepared calibration check solution, and the instrument drift with an instrument performance check solution (3.4–3.8).

6. Measurement

   Nebulisation of the test solution, excitation in the plasma, measurement of the intensity of the selenium line with background correction (clause 4).

7. Limits of detection and quantification

   From the standard deviation s₀ of the results of at least 3 measurements of the reagent blank: limit of detection 3 s₀, limit of quantification 9 s₀ (3.10–3.11).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard states that the tests are to be carried out by suitably trained staff, and that safety practices and compliance with national regulations are the responsibility of the user
• Acids for digestion and solutions of toxic elements are handled according to their safety data sheets

Frequently asked questions