📊 Cations in Water and Waste Water — Ion Chromatography (IC)

Physicochemistry PN-EN ISO 14911

Overview

STATUS (as of 03.11.2026). PN-EN ISO 14911:2002 — Polish version, published on 21.03.2002, implements EN ISO 14911:1999 and ISO 14911:1998 [IDT]; the PKN catalogue card has no note of withdrawal. ISO 14911:1998 (first edition) has the stage “confirmed after review” (90.93) in the ISO catalogue. The standard covers cations only — dissolved anions (bromide, chloride, fluoride, nitrate, nitrite, phosphate, sulfate) are determined according to PN-EN ISO 10304-1 (a separate method in the Knowledge Base), and bromate according to PN-EN ISO 15061.

SCOPE (clause 1, Table 1). The dissolved cations Li⁺, Na⁺, NH₄⁺, K⁺, Mn²⁺, Ca²⁺, Mg²⁺, Sr²⁺ and Ba²⁺ in water (e.g. drinking water, surface water) and in waste water; the applicability to waste water is proved in each case. Typical working ranges with a 10 µl loop: lithium 0.01–1 mg/l; sodium, ammonium and potassium 0.1–10 mg/l; manganese, calcium, magnesium and strontium 0.5–50 mg/l; barium 1–100 mg/l. The range is limited by the ion-exchange capacity of the separator column — if necessary the sample is diluted, and for lower concentrations a 100 µl loop is used.

PRINCIPLE (clause 4). The cations are separated by liquid chromatography on a low-capacity cation exchanger; the mobile phase is usually an aqueous solution of mono- and dibasic acids. They are detected by conductivity: the detector is often combined with a suppressor device (e.g. an anion exchanger), which reduces the conductivity of the eluent and transforms the separated cations into their corresponding bases; without suppression, the difference between the ion equivalent conductivities is measured directly after the column — it should be as high as possible, and the temperature of the detector cell stable within ± 0.1 °C. The concentration is determined by calibration of the overall procedure, in particular cases by the method of standard addition.

ESSENTIAL MINIMUM REQUIREMENTS (clauses 5 and 8). Resolution of any pair of peaks not below R = 1.3, and interfering cations must not interfere with the cations of interest at concentrations of 0.1 mg/l Li⁺, 1 mg/l Na⁺ and NH₄⁺, 2 mg/l K⁺, Mn²⁺, Ca²⁺ and Mg²⁺, 5 mg/l Sr²⁺ and 10 mg/l Ba²⁺. Conductivity detection with or without a suppressor device; calibration in the linear (ISO 8466-1) or second-order (ISO 8466-2) working range; a validity check of the calibration function, replicate determinations if necessary.

INTERFERENCES (clause 3). Organic compounds such as amino acids and aliphatic amines can interfere with the determination. Without a strong complexing agent in the mobile phase (e.g. pyridine-2,6-dicarboxylic acid, PDA) and without suppression, cross-interferences from other cations (Zn²⁺, Ni²⁺, Cd²⁺) can occur; cross-sensitivities (e.g. from manganese) depend on the selectivity of the column — if the requirements of clause 8 cannot be met, the sample is diluted. With large differences in concentration the determinations of NH₄⁺ and Na⁺ interfere with each other. Solids and organic compounds (mineral oils, detergents, humic acids), which shorten the lifetime of the column, are eliminated from the sample.

ELUENTS AND SOLUTIONS (clause 6). Water with a conductivity below 0.01 mS/m and without particles larger than 0.45 µm. The eluent composition is chosen according to the column manufacturer’s instructions; the standard gives examples — with suppression: hydrochloric acid 0.04 mol/l with DL-2,3-diaminopropionic acid monohydrochloride (DAP) 0.004 mol/l (storage at 4–6 °C, renewed every 7 days) or methanesulfonic acid 0.02 mol/l (every 3 days); without suppression: nitric, tartaric or oxalic acid, usually at 0.001–0.01 mol/l, e.g. tartaric acid 0.004 mol/l with PDA 0.001 mol/l (pH 2.8) or nitric acid 0.02 mol/l (both renewed every 3 days). The eluents are degassed and stored in the dark. Stock solutions of 1000 mg/l of each cation are prepared from nitrates (ammonium — from ammonium chloride) with the addition of nitric acid in polyethylene flasks; they are stable for 6 months at 4–6 °C, and for manganese, calcium and magnesium the titre is adjusted (ISO 6333, ISO 7980 or ISO 6058 and ISO 6059). From them a mixed standard solution is prepared (stable for a week at 2–6 °C) and, on the day of use, 5–10 calibration solutions.

REGULATIONS. Waste water: PN-EN ISO 14911 is one of the reference methods for ammonium nitrogen, barium, potassium and sodium (Dz.U. 2019 item 1311, Annex 12 items 6, 10, 48 and 55). Monitoring of surface and groundwater bodies: a method for calcium, magnesium and ammonium nitrogen (Dz.U. 2021 item 1576, Annex 8 points 3.3.6, 3.3.7 and 3.5.1). Water intended for human consumption: parametric values, among others, for ammonium ion 0.50 mg/l and sodium 200 mg/l (Dz.U. 2026 item 748, Annex 1 part C); the regulation does not specify a method.

SECOND SOURCE. The textbook “Chemia wody” [Water chemistry] (Wrocław University of Science and Technology 2024, section 4.17.1) describes the determination of lithium, sodium, potassium, ammonium, calcium and magnesium in waters and waste water according to PN-EN ISO 14911: samples in containers not washed with acids or alkaline detergents, filtration through a 0.45 µm membrane filter discarding the first portion of the filtrate, storage at 4–6 °C, calibration with ready-made standard solutions.

WHAT WE DO NOT GIVE HERE. The publicly available text of the standard ends with clause 8 (quality requirements for the separator column). Sample pretreatment (clause 9), the procedure (clause 10), the calculation of the result and precision data are outside it — which is why we do not give sample volumes, retention times, limits of detection or precision data.

Method principle

The cations are separated by liquid chromatography on a low-capacity cation exchanger, and the mobile phase is usually an aqueous solution of mono- and dibasic acids. The separated cations are measured with a conductivity detector — with a suppressor device, which reduces the conductivity of the eluent and transforms the cations into their corresponding bases, or without suppression, when the difference between the ion equivalent conductivities is measured after the column. The concentration is determined by calibration of the overall procedure, in particular cases by the method of standard addition.

Applications

• Water, e.g. drinking and surface water, and waste water — lithium, sodium, ammonium, potassium, manganese, calcium, magnesium, strontium and barium; the applicability to waste water is proved in each case (clause 1)
• Waste water — one of the reference methods for ammonium nitrogen, barium, potassium and sodium (Dz.U. 2019 item 1311, Annex 12 items 6, 10, 48, 55)
• Monitoring of surface and groundwater — calcium, magnesium, ammonium nitrogen (Dz.U. 2021 item 1576, Annex 8 points 3.3.6, 3.3.7, 3.5.1)
• Water intended for human consumption — among others ammonium ion (0.50 mg/l) and sodium (200 mg/l) (Dz.U. 2026 item 748, Annex 1 part C)

Key parameters

Standard

Standard number

PN-EN ISO 14911:2002

Title (PL)

Jakość wody — Oznaczanie Li⁺, Na⁺, NH₄⁺, K⁺, Mn²⁺, Ca²⁺, Mg²⁺, Sr²⁺ i Ba²⁺ za pomocą chromatografii jonowej — Metoda dla wód i ścieków

Title (EN)

Water quality — Determination of dissolved Li⁺, Na⁺, NH₄⁺, K⁺, Mn²⁺, Ca²⁺, Mg²⁺, Sr²⁺ and Ba²⁺ using ion chromatography — Method for water and waste water

Step-by-step procedure

1. Sampling and sample pretreatment

   Take the sample according to ISO 5667-1, ISO 5667-2 and ISO 5667-3 (normative references); eliminate solids and organic compounds from the sample, because they shorten the lifetime of the column (3.5) — details in clause 9, which is outside the available text.

2. Eluent

   Choose the eluent for the column and detector according to the column manufacturer’s instructions — with suppression e.g. methanesulfonic acid 0.02 mol/l, without suppression e.g. nitric acid 0.02 mol/l; degas it, avoid renewed gas pick-up and store it in the dark (6.16).

3. Standard solutions

   From the 1000 mg/l stock solutions prepare a mixed standard solution (Table 3), and from it, on the day of use, 5–10 calibration solutions in 100 ml polyethylene flasks with 0.1 ml of nitric acid 1 mol/l (6.18, 6.19).

4. Calibration

   Establish the linear (ISO 8466-1) or second-order (ISO 8466-2) working range; in particular cases use the method of standard addition (clauses 4, 5).

5. Column check

   The resolution of any pair of peaks must be at least 1.3, and interfering cations must not interfere with the cations of interest at the concentrations of clause 8; if the requirements are not met, dilute the sample (3.3, clause 8).

6. Measurement

   Introduce the sample through the sample loop (e.g. 10 µl, for lower concentrations 100 µl), measure the conductivity and read the concentrations from the calibration function of the overall procedure (clauses 1, 4).

7. Quality control

   Check the validity of the calibration function; if necessary carry out replicate determinations (clause 5).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Hydrochloric acid 7.7 mol/l, methanesulfonic acid and nitric acid used for eluents are prepared according to their safety data sheets

Frequently asked questions