💧 Determination of total and free cyanide in water by flow injection analysis (FIA) — for total cyanide the complexes are decomposed in the flow system by UV-B radiation at pH 3.8 and in a thermal reactor at 85 °C, hydrogen cyanide passes through a hydrophobic membrane into sodium hydroxide solution and gives a red colour with chloramine-T, pyridine-4-carboxylic acid and 1,3-dimethylbarbituric acid; for free cyanide the UV lamp is switched off; range 2–500 µg/l, PN-EN ISO 14403-1

Physicochemistry PN-EN ISO 14403-1

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 14403-1:2012 (English version), in full (our translation): “Methods are specified for the determination of cyanide in various types of water (such as ground, drinking, surface, leachate and waste water) with concentrations from 2 to 500 micrograms/l, expressed as cyanide ions, in the undiluted sample. The range of application can be extended by changing the conditions, e.g. by diluting the original sample or using different injection volumes. The method is described for a mass concentration range from 20 to 200 micrograms/l”. We read the text of the standard in two samples: SIST EN ISO 14403-1:2013 (English text of EN ISO 14403-1:2012) — title pages, European foreword, contents, ISO foreword and introduction; ISO 14403-1:2012 (French version) — from the contents through Clauses 1–5 up to and including 6.21 of Clause 6 (reagents). Outside the samples remain Clauses 7–12 (apparatus, sampling and sample preparation, procedure, calculation, expression of results, test report) and Annexes A–C (examples of flow systems, determination of the real concentration of the potassium cyanide solution, performance data).

ACCORDING TO THE TEXT OF ISO 14403-1:2012 (Clauses 1–5, 6.1–6.21). The standard was prepared by ISO/TC 147 “Water quality”, subcommittee SC 2, in collaboration with CEN/TC 230 (secretariat DIN); CEN approved it on 13 July 2012 without modification; it superseded EN ISO 14403:2002. Part 2 of the same standard describes continuous flow analysis (CFA). Scope (1): ground, drinking and surface water, leachates and waste water, concentrations from 2 µg/l to 500 µg/l as cyanide ions in the undiluted sample; the range is changed by diluting the sample or changing the injection volume; the standard describes a suitable mass concentration range of 20–200 µg/l; seawater can be analysed after adapting reagents and calibration solutions to the salinity, with a possible change in sensitivity. Definitions (3): free cyanide (easily liberatable) is the sum of cyanide ions and cyanide bound in weak metal complexes that release HCN at pH 3.8; total cyanide is free cyanide plus stronger metal cyanide complexes — except complexes of gold, cobalt, platinum, ruthenium and rhodium, which may be recovered only partially. Interferences (4): oxidizing agents such as chlorine decompose most cyanides — if they cannot be excluded, the sample is treated immediately after sampling: a drop is put on potassium iodide/starch paper, and a blue colour means that sodium thiosulfate must be added a few crystals at a time until a drop no longer colours the paper; at the sampling point it shall be investigated whether the sample is stable over the storage time and whether preservation is effective. Sulfide interferes from 20 mg/l: when lead acetate paper shows sulfide, an additional 25 ml of preserved sample (pH > 12) is treated with powdered lead carbonate until a drop no longer blackens the paper, and filtered through a dry filter — with moderation, because excess lead and long contact bind cyanide in the precipitate. Aldehydes and ketones may bind cyanide — addition of ethylenediamine prevents this. Nitrite interferes above 2 mg/l — sulfamic acid in the pH 3.8 buffer removes it; sulfite — above 1 mg/l. Particles larger than 0.1 mm clog the tubing — they are removed by filtration; thiocyanate may cause a slight positive bias, and cyanide impurities in the thiocyanate itself may cause a significant one. Principle (5.1, 5.2): for total cyanide the complexes are decomposed at pH 3.8 by UV-B radiation (emission maximum above 310 nm and not above 400 nm); a coil of FEP or PTFE cuts off radiation below 290 nm so that thiocyanate is not converted into cyanide; decomposition is assisted by hydrolysis in a thermal reactor (85 °C); hydrogen cyanide present at pH 3.8 passes at 30–40 °C through a hydrophobic membrane and is absorbed in sodium hydroxide solution, then reacts with chloramine-T to cyanogen chloride, which gives a red colour with pyridine-4-carboxylic acid and 1,3-dimethylbarbituric acid. For free cyanide the UV-B lamp is switched off and thermal decomposition takes place in a citrate/succinate buffer; to release cyanide from the nickel complex, 50 µl of tetraethylenepentamine solution per 30 ml of sample is added before analysis. Reagents (6): warning — KCN, K2Zn(CN)4, their solutions and wastes are toxic; water of grade 1 according to ISO 3696; hydrochloric acid 1 mol/l; sodium hydroxide 0.4 mol/l (carrier solution), 1.0 mol/l and 0.01 mol/l; tetraethylenepentamine solution — 0.75 g in 250 ml of water, stable for one month (free cyanide only); potassium cyanide solution 1000 mg/l CN — 2500 mg ± 1 mg KCN in NaOH 0.01 mol/l to 1000 ml, with the real concentration established according to Annex B; alternatively commercial potassium tetracyanozincate solution 1000 mg/l ± 2 mg/l, stable for six months at 2–8 °C; cyanide solution 10 mg/l (1 ml of stock solution to 100 ml), stable for one week at 2–8 °C; at least five calibration solutions evenly over the working range — for example 20, 60, 100, 120, 160 and 200 µg/l from an intermediate solution of 1 mg/l, stable for two days at 2–8 °C. Buffer pH 3.8 for gas diffusion: 10.5 g NaOH, 12.0 g Na2EDTA, 15.2 g succinic acid, 27.0 g citric acid monohydrate and 12.5 g sulfamic acid to 500 ml, stable for one week in a refrigerator (1–5 °C) — the citrate/succinate buffer is more effective at pH 3.8 than a pure citrate buffer, citrate and EDTA promote decomposition of hexacyanoferrate, EDTA prevents precipitation of insoluble cyanides in the thermal reactor, and sulfamic acid removes nitrite. Buffer for the final photometric measurement: 7.0 g NaOH in 250 ml, 35.4 g succinic acid, to 500 ml — pH about 4.3, and when mixed with the NaOH 0.4 mol/l carrier it shall give pH 5.2. Chloramine-T solution: 0.14 g in 100 ml of water, stable for one week at 1–5 °C, best prepared daily. Colour reagent: 7.0 g NaOH in about 500 ml of water, 16.8 g ± 0.1 g 1,3-dimethylbarbituric acid and 13.6 g ± 0.1 g pyridine-4-carboxylic acid, to about 975 ml, pH 5.2 if necessary, to 1000 ml, stirring for 1 h at 30 °C, filtration through a fluted filter — stable for one month at 2–5 °C. Thiocyanate solution (to check that thiocyanate is not converted into cyanide): 373 mg ± 1 mg KSCN to 1000 ml in NaOH 0.01 mol/l, corresponding by calculation to 100 mg/l CN; stable for two months in an amber bottle at 1–5 °C.

STATUS (catalogue card as of 03.10.2026). The card of PN-EN ISO 14403-1:2012 (English version, published 30-08-2012, 17 pages, price group J) has no “Withdrawn” header: Health, Environment and Medicine Sector, KT 121 Water Quality — Chemical Testing — Inorganic Substances, ICS 13.060.50, “Introduces: EN ISO 14403-1:2012 [IDT], ISO 14403-1:2012 [IDT]”, “Supersedes: PN-EN ISO 14403:2004 — Polish version”. A Polish language version of this edition is not in the PKN search (term “PN-EN ISO 14403-1”, 03.10.2026) — only the English version exists. In the iTeh catalogue (read 03.10.2026) ISO 14403-1:2012 has the status “Published” and stage 90.93 “International Standard confirmed” — the ISO document was confirmed in the systematic review.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read 03.10.2026). The number 14403-1 appears in 6 records at 6 laboratories: AB 322, AB 438, AB 486, AB 492, AB 537, AB 581 — everywhere as “PN-EN ISO 14403-1:2012”. In the current scopes on the PCA website (read 03.10.2026, issues from 17.11.2025 to 01.10.2026) the notation is the same. The “Laboratories” tab (“PN-EN ISO 14403-1”) shows the same 6 laboratories; checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (PCA items). Water and water intended for human consumption (AB 438, AB 486, AB 492, AB 537, AB 581) and water and waste water (AB 322); technique in all items — flow injection analysis (FIA), in five with spectrophotometric detection. “Total cyanide” is given by AB 438, AB 492 and AB 581, plain “Cyanide concentration” by AB 486 and AB 537, “total and free cyanide” only by AB 322. Ranges: (10–100) µg/l (AB 438, AB 581), (10–90) µg/l (AB 492), (5.0–80) µg/l (AB 486), (5.0–200) µg/l (AB 537) and (0.005–5.0) mg/dm3 (AB 322). All lower limits lie within the range of the standard (from 2 µg/l); the upper limit of AB 322 — 5.0 mg/l, i.e. 5000 µg/l — is ten times higher than 500 µg/l of Clause 1, which the standard allows by diluting the sample or changing the injection volume. None of these six laboratories has Part 2 of this standard (CFA method, entry on PN-EN ISO 14403-2) in its current PCA document — the number 14403-2 does not occur once in their scopes (search in the text of the six documents, 03.10.2026).

WHERE A SEEMINGLY CORRECT RESULT IS EASY. At sampling: chlorine and other oxidants decompose cyanide in the bottle — a sample not tested with iodide/starch paper and not dechlorinated with thiosulfate immediately after sampling cannot be corrected later, and the result is too low without any signal (4.1). At preparation: sulfide interferes from 20 mg/l, and excess lead carbonate and long contact during its removal bind cyanide in the precipitate and lower the result (4.2); aldehydes and ketones bind cyanide. At measurement of total cyanide: UV radiation shorter than 290 nm converts thiocyanate into cyanide — the FEP or PTFE coil and the UV-B lamp (above 310 nm) are part of the method, not optional equipment (5.1); the thiocyanate solution of 6.21 serves to check that this does not happen. For free cyanide: without tetraethylenepentamine cyanide bound in the nickel complex is not released (5.2). At the result: “total cyanide” according to this standard does not fully include complexes of gold, cobalt, platinum, ruthenium and rhodium (3.2) — the result is not the entire amount of cyanide in the sample; the real concentration of the KCN solution is established according to Annex B, not from the 2500 mg weighed portion alone (6.18.1).

WHAT WE DO NOT GIVE. We did not read Clauses 7–12 and Annexes A–C, so we do not give the design of the flow system, injection conditions, measuring wavelength, the method of sample preservation (the standard cites ISO 5667-3), the calculation or precision data. Nor do we give limit values for cyanide in drinking water or waste water, because we did not read the texts of regulations for this entry.

Method principle

In the flow injection system the sample is mixed with a buffer of pH 3.8; for total cyanide the metal cyanide complexes are decomposed by UV-B radiation (above 310 nm, without the component below 290 nm that would convert thiocyanate into cyanide) and heating in a reactor at 85 °C, for free cyanide the lamp is switched off. The released hydrogen cyanide passes at 30–40 °C through a hydrophobic membrane into sodium hydroxide solution, and chloramine-T converts it into cyanogen chloride, which with pyridine-4-carboxylic acid and 1,3-dimethylbarbituric acid gives a red colour measured by a flow photometer.

Applications

• Ground, drinking and surface water, leachates and waste water — total and free cyanide, 2–500 µg/l in the undiluted sample (Clause 1)
• Higher concentrations — after diluting the sample or changing the injection volume; seawater — after adapting the reagents to the salinity (Clause 1)
• Water and water intended for human consumption, water and waste water — in the accreditation scopes of 6 laboratories at PCA

Key parameters

Standard

Standard number

PN-EN ISO 14403-1:2012

Title (PL)

Jakość wody — Oznaczanie cyjanków ogólnych i wolnych przy zastosowaniu analizy przepływowej (FIA i CFA) — Część 1: Metoda wstrzykowej analizy przepływowej (FIA)

Title (EN)

Water quality — Determination of total cyanide and free cyanide using flow analysis (FIA and CFA) — Part 1: Method using flow injection analysis (FIA)

Step-by-step procedure

1. Sampling and preservation

   Immediately after sampling check oxidants with iodide/starch paper and, if necessary, add sodium thiosulfate; check sulfide with lead acetate paper. PN-EN ISO 14403-1:2012 current (PKN catalogue card as of 03.10.2026).

2. Removal of interferences

   Sulfide — lead carbonate on an additional 25 ml of sample of pH > 12 and filtration; nitrite is removed by sulfamic acid in the buffer; filter off particles > 0.1 mm.

3. Reagents and standards

   Buffers, chloramine-T, colour reagent; at least 5 calibration solutions within the working range (e.g. 20–200 µg/l), KCN solution standardized according to Annex B.

4. Measurement

   Total cyanide — with the UV-B lamp and the 85 °C reactor; free cyanide — lamp off, after adding tetraethylenepentamine (50 µl per 30 ml); diffusion of HCN through the membrane, colour reaction, flow photometer. We do not give the details of the procedure (Clause 9).

5. Thiocyanate check

   The thiocyanate solution (by calculation 100 mg/l CN) shows whether the system converts thiocyanate into cyanide (6.21, 4.3).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Potassium cyanide, potassium tetracyanozincate, their solutions and wastes are toxic and shall be disposed of appropriately (warning in Clause 6); on acidification hydrogen cyanide is released
• The standard requires tests to be carried out by suitably trained staff, and safety practices are established by the user (warning at the beginning of the standard)
• Lead carbonate and lead acetate are toxic — treat precipitates from sulfide removal as hazardous waste

Frequently asked questions