🌿 Determination of total cyanide and easily liberatable cyanide in soil by continuous-flow analysis (CFA) with automated distillation — the soil is extracted with 2.5 mol/l NaOH for 16 h and the extract diluted 100-fold; for total cyanide the complexes are decomposed in the flow by a UV-B lamp after adding a pH 3.8 buffer, for easily liberatable cyanide zinc sulfate precipitates the iron cyanides; HCN distilled at 125 °C reacts with chloramine-T, pyridine-4-carboxylic acid and 1,3-dimethylbarbituric acid, and the dye is measured at 606 nm; complex cyanides — by difference; soils with contents above 1 mg/kg dry matter, PN-EN ISO 17380

Environment PN-EN ISO 17380

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in two iTeh samples. SIST EN ISO 17380:2013 (English text): the European part (title page of EN ISO 17380 of June 2013, EN foreword, endorsement notice), title page of ISO 17380:2013, contents, ISO foreword and introduction — the sample ends before Clause 1. ISO 17380:2013 (French text, “Qualité du sol — Détermination des cyanures totaux et des cyanures aisément libérables — Méthode d’analyse en flux continu”): Clauses 1–4, Clause 5 up to 5.3.3.1 (potassium thiocyanate control solution) — the sample ends on page 5. We do not read Clauses 6–12 or Annexes A–C; we know their titles from the contents.

ACCORDING TO THE TEXT OF ISO 17380:2013. The second edition of 15.06.2013 was prepared by ISO/TC 190 “Soil quality”, Subcommittee SC 3 “Chemical methods and soil characteristics”; it cancels and replaces the first edition ISO 17380:2004, technically revised. Contents: 1 Scope, 2 Normative references, 3 Terms and definitions, 4 Principle (4.1 pretreatment of soil samples, 4.2 total cyanide, 4.3 easily liberatable cyanide), 5 Reagents, 6 Apparatus (laboratory glassware and equipment, continuous flow analysis system, shaking machine), 7 Sampling, sample preparation and extraction, 8 Working range, 9 Procedure (9.2 checking the analysis system, 9.3 calibration graph, 9.4 measurement of samples, 9.5 cleaning the system), 10 Calculation of cyanide content, 11 Precision, 12 Test report, Annex A (informative) “Recovery and repeatability”, Annex B (informative) on the continuous-flow automatic distillation apparatus, Annex C (informative) “Alternative distillation buffer (pH = 3.8)”, bibliography. Introduction: cyanides may be present in soil as cyanide ions and as complex cyanides; they are determined as easily liberatable or total cyanide, and complex cyanides are calculated by subtracting easily liberatable from total cyanide. Flow methods automate wet chemistry and suit large series of water or soil extracts; in CFA the sample is dosed into a flow system where it reacts with reagents, and the product is measured in a flow photometer. ISO 11262 describes a manual photometric and titrimetric method for total cyanide in soil — results may differ slightly, but the differences are not considered very significant; the easily liberatable cyanide test was removed from ISO 11262 because its validation data were very poor. For water ISO 14403-1 and ISO 14403-2 apply; the analytical procedure of ISO 14403-2 is identical to that of ISO 17380. Scope (1): photometric determination of total and easily liberatable cyanide in soil by continuous flow analysis with automated distillation; all types of soil with cyanide content, expressed as cyanide ions, above 1 mg/kg dry matter; note: sulfide above 40 mg/kg dry matter interferes — the symptoms are split peaks and slow decay of the detector signal, and the only remedy is dilution of the extract. References (2): ISO 3696 (water for analysis), ISO 9297 (chloride by the Mohr method), ISO 11262 (total cyanide in soil), ISO 11465 (dry matter and water by gravimetry), ISO 14507:2003 (pretreatment of samples for organic contaminants). Definitions (3): total cyanide — the sum of easily liberatable cyanide and cyanide bound in metal cyanides, excluding thiocyanate ions and with only partial decomposition of cobalt, gold and platinum complexes; easily liberatable cyanide — the sum of easily liberatable cyanide ions and cyanide bound in simple metal cyanides (as CN) under the conditions of this method — it includes the weakly bound complexes tetracyanonickelate(II) and dicyanomercurate(II) and up to 5 % of strongly bound hexacyanoferrates; organic compounds (e.g. acetonitrile) are not determined; in gold-production wastes it is called weak-acid-dissociable cyanide; complex cyanides — the difference between total and easily liberatable cyanide. Principle (4): the soil sample is extracted with 2.5 mol/l NaOH for 16 h and the extract diluted 100-fold (to 0.025 mol/l NaOH). Total cyanide: the complexes are decomposed in the flow after adding a buffer of initial pH 3.8, by a UV-B lamp in a borosilicate glass coil, which absorbs radiation below 290 nm and prevents photolysis of thiocyanates to cyanide; HCN is separated by in-line distillation at a heating-block temperature of 125 ± 2 °C; cyanide with chloramine-T gives cyanogen chloride, which with pyridine-4-carboxylic acid and 1,3-dimethylbarbituric acid gives a purple colour measured at 606 nm (with an interference filter 600 ± 10 nm); after mixing the sample with the buffer at 1.0 : 0.42 the final pH is 4.0, and fluctuations of the distillation pH between 3.8 and 5.7 change HCN recovery by only a few percent. Easily liberatable cyanide: without UV irradiation, zinc sulfate is added before distillation, which precipitates iron cyanide complexes as zinc cyanoferrates; then as for total cyanide (zinc sulfate replaces water as a reagent). Reagents (5): analytical grade, water of grade 1 or 2 according to ISO 3696; HCl 37 %, 1 and 0.1 mol/l; NaOH 2.5 mol/l (100 g/l, in a polyethylene bottle), 1 mol/l and 0.025 mol/l; detergent solution (polyoxyethylene lauryl ether, n ≈ 23, 30 g in 100 ml of water — commercially Brij-35); indicator p-dimethylaminobenzylidene rhodanine 0.02 g in 100 ml of acetone (at least a week in the dark at (5 ± 3) °C); silver nitrate 0.01 mol/l (1.689 7 g/l, concentration checked every two weeks with sodium chloride according to ISO 9297, new solution monthly) and 0.001 mol/l (daily); ethanol 20 % (V/V). Distillation buffer pH 3.8: 50 g of citric acid monohydrate in 200 ml of water, 120 ml of 1 mol/l NaOH, to 500 ml — stable 3 months in the dark at (5 ± 3) °C (another buffer for flow-stability problems — Annex C); zinc sulfate 10 g ZnSO4·7H2O in 1000 ml (stable at least a year); photometric buffer pH 5.2 with potassium hydrogen phthalate and detergent; chloramine-T 2.0 g/l (a month in the dark in a refrigerator); colour reagent pH 5.2 — 7.0 g NaOH, 16.8 g 1,3-dimethylbarbituric acid and 13.6 g pyridine-4-carboxylic acid in 1000 ml, stirred 1 h at 30 °C and filtered (3 months, filtered before use); sampler rinsing solution NaOH 0.025 mol/l. Standards (5.3): concentrated solutions stable at least 3 months, diluted at least a week (in the dark, refrigerated); 100 mg/l CN− solution from 0.250 g KCN in 0.025 mol/l NaOH, with concentration determined by titration with silver nitrate against rhodanine (from yellow to yellow-red): ρCN = V1 · c(AgNO3) · M(2CN) / V, M(2CN) = 52 g/mol, V = 10 ml — commercial standards, e.g. K2Zn(CN)4, may be used; 1 mg/l CN− solution (2.5 ml to 250 ml); potassium thiocyanate control solution equivalent to 100 mg/l CN− (0.373 g KSCN dried at 105 °C).

ACCORDING TO THE FOREWORD OF EN ISO 17380:2013. The document was prepared by ISO/TC 190 in collaboration with CEN/TC 345 “Characterization of soils”; CEN approved it on 08.06.2013 without modification from ISO 17380:2013; national standards had to implement it, and conflicting ones to withdraw, by December 2013 at the latest.

STATUS (as of 03.10.2026). In the PKN search (query “17380”, 03.10.2026) PN-EN ISO 17380:2013-08 (English version, “Wprowadza: EN ISO 17380:2013 [IDT], ISO 17380:2013 [IDT]”) carries no withdrawal note, and PN-ISO 17380:2010 (Polish version, introduced ISO 17380:2004) — “Wycofana i zastąpiona przez PN-EN ISO 17380:2013-08 – wersja angielska”; the third result, PKN-CEN/TS 17380:2023-10, concerns intelligent transport systems. Card of PN-EN ISO 17380:2013-08: publication date 28.08.2013, 30 pages, KT 191 Chemii Gleby, no withdrawal note. In the iTeh catalogue (read 03.10.2026) ISO 17380:2013 has the status “Published”, stage 90.93 (International Standard confirmed).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 03.10.2026). The number 17380 appears in 4 records at 3 laboratories: AB 213 (2), AB 313, AB 1095. In the current PCA documents (read 03.10.2026; AB 213 issue no. 28 of 17.04.2026, AB 1095 issue no. 25 of 03.07.2026, AB 313 issue no. 43 of 08.07.2026) the number appears in 4 lines at the same 3 laboratories; in each document the number of page markers equals the number of PDF pages, without repetitions; a search of all PCA documents downloaded from the BIP on 03.10.2026 found no laboratories outside the database copy. Form “PN-EN ISO 17380:2013-08” (AB 213, AB 1095; the letter “M” on the right of the AB 1095 line is in this document a location code — the laboratory in Mysłowice, not a method designation) and “PN-EN ISO 17380:2013” (AB 313). None of these items is suspended. The “Laboratories” tab (query “PN-EN ISO 17380”) shows all 3 laboratories — checked by a tab query on the labcoda.pl production server on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Object: soil (AB 213, AB 313, AB 1095) and building materials: sand, aggregate, slag (AB 213). Characteristic: free and total cyanide content (AB 213), free, total cyanide content (AB 1095), free and bound cyanide content (AB 313); in the database copy AB 213 and AB 1095 also have “bound cyanide content (calculated)”. Ranges: (0.50–100) mg/kg (AB 213 — soil and building materials, AB 313), (1.0–100) mg/kg (AB 1095). Technique: continuous flow analysis (CFA) with spectrophotometric detection at all.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Lower limit: the scope of the standard covers soils with cyanide contents above 1 mg/kg dry matter (1), while AB 213 and AB 313 give a range from 0.50 mg/kg — we have not read Clause 8 “Working range”, so we do not know whether the standard says anything about lower concentrations. Matrix: the standard concerns soil; AB 213 also applies it to sand, aggregate and slag. Names: the standard speaks of easily liberatable cyanide (in the Polish title “łatwo rozkładalne”), while the scopes say “free” — definition 3.2 also includes simple metal cyanides, weak nickel and mercury complexes and up to 5 % of hexacyanoferrates, so it is not only free CN− ions. Bound cyanide: according to 3.3 it is the difference of two measurements of this method, not a separate measurement. Sulfide: above 40 mg/kg d.m. it interferes, the symptom being split peaks; the only remedy is dilution of the extract (1). Thiocyanate: it is not included in total cyanide — which is why the borosilicate glass coil cuts off UV below 290 nm (4.2); the KSCN control solution (5.3.3.1) serves to check this condition. Standards: the concentration of the KCN standard is determined by titration with silver nitrate, whose titre is checked every two weeks (5.1.9, 5.3.2.1).

WHAT WE DO NOT GIVE. The apparatus, extraction procedure and sample amount, working range, calibration, calculation of the content in soil, precision and recovery data (Clauses 6–12, Annexes A–C) are not quoted — they lie outside the samples. We do not give permissible cyanide values for soil from regulations.

Method principle

The soil is extracted with 2.5 mol/l NaOH for 16 h and the extract diluted 100-fold. In the flow system, for total cyanide, a pH 3.8 buffer is added and the complexes are decomposed by a UV-B lamp (borosilicate glass cuts off radiation below 290 nm, protecting thiocyanates); for easily liberatable cyanide, instead of UV, zinc sulfate is added, which precipitates iron cyanides. HCN distilled in-line at 125 °C gives cyanogen chloride with chloramine-T, and this with pyridine-4-carboxylic and 1,3-dimethylbarbituric acid a purple dye measured at 606 nm. Complex cyanides = total − easily liberatable.

Applications

• Total and easily liberatable cyanide in all types of soil with contents above 1 mg/kg dry matter (1)
• Complex cyanides — from the difference of two determinations (3.3)
• Soil and sand, aggregate and slag — items in the accreditation scopes of 3 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN ISO 17380:2013-08

Title (PL)

Jakość gleby — Oznaczanie cyjanków ogólnych oraz cyjanków łatwo rozkładalnych — Metoda z zastosowaniem analizy przepływowej ciągłej

Title (EN)

Soil quality — Determination of total cyanide and easily liberatable cyanide — Continuous-flow analysis method

Step-by-step procedure

1. Extraction

   Soil with 2.5 mol/l NaOH for 16 h; extract diluted 100-fold (4.1; details in Clause 7, outside the sample). PN-EN ISO 17380:2013-08 with no withdrawal note in PKN (03.10.2026).

2. Total cyanide

   In the flow, pH 3.8 buffer, UV-B decomposition in a borosilicate coil, in-line distillation 125 ± 2 °C (4.2).

3. Easily liberatable cyanide

   Without UV, with zinc sulfate before distillation at 125 °C (4.3).

4. Detection

   HCN + chloramine-T → cyanogen chloride → dye with pyridine-4-carboxylic and 1,3-dimethylbarbituric acid, 606 nm (4.2).

5. Result

   Content in mg/kg dry matter (calculation in Clause 10, outside the sample); complex cyanides = total − easily liberatable (3.3).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Potassium cyanide and hydrogen cyanide — highly toxic; work under a fume hood, alkaline solutions, no contact with acids outside the system
• Sodium hydroxide 2.5 mol/l and hydrochloric acid 37 % — corrosive, eye and hand protection

Frequently asked questions