🌿 Determination of mercury in digests of sewage sludge, treated biowaste and soil obtained with aqua regia (EN 16174) or nitric acid (EN 16173) — mono- and divalent mercury is reduced with tin(II) chloride (recommended) or sodium borohydride to elemental mercury, stripped with a carrier gas in a closed system into the spectrometer cell and its absorbance measured at 253.7 nm against a calibration curve; lower working range limit 0.03 mg/kg dry matter, PN-EN 16175-1

Environment PN-EN 16175-1

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of SIST EN 16175-1:2017 (English text of EN 16175-1:2016): from the European foreword through the introduction with Table 1 and Clauses 1–5 to 6.2 (atomic absorption spectrometer) on page 7. Outside the sample remain the rest of the apparatus, procedure, calibration, calculation, precision, test report and Annex A with the validation results.

ACCORDING TO THE TEXT OF EN 16175-1:2016. The standard was prepared by CEN/TC 444 “Test methods for environmental characterization of solid matrices”, whose secretariat is held by NEN; national implementation was due by April 2017 at the latest; the document supersedes CEN/TS 16175-1:2013, and the previous edition was prepared under mandate M/330 of the European Commission (standards on sampling and analysis for sludge, treated biowaste and soil). EN 16175 “Sludge, treated biowaste and soil — Determination of mercury” has two parts: 1 — CV-AAS, 2 — cold-vapour atomic fluorescence spectrometry (CV-AFS). Table 1 (validation, results in Annex A): sludge — municipal sludge, biowaste — compost, soil — soil; a warning on laboratory practice and the user’s responsibility for safety; tests should be carried out by trained staff. Scope (1): determination of mercury in aqua regia or nitric acid digests of sludge, treated biowaste and soil obtained according to EN 16173 or EN 16174, by CV-AAS; lower working range limit 0.03 mg/kg (dry matter basis). References (2): EN 15934, EN 16173, EN 16174, EN ISO 3696. Principle (3): mono- and divalent mercury is reduced to the elemental form by tin(II) chloride or sodium borohydride in acid medium, stripped from the solution in a closed system, and the mercury vapour as an atomic gas passes through a cell in the light path of the spectrometer; absorbance is measured at 253.7 nm and concentrations calculated from a calibration curve; according to a note, the solution matrix is dominated by the digestion acids, and tin(II) chloride is recommended because sodium borohydride reduces many elements present in soil, sludge and waste extracts to the elemental state, which may cause matrix problems in particular circumstances — though it can still be used; the range 1–10 µg/l in the digest, corresponding to 0.03–0.3 µg/g for a 3.0 g sample, is determined directly, higher concentrations after dilution, and sensitivity can be increased by amalgamation. Interferences (4): samples are digested with strong oxidizing acids, so there are no interferences from organic substances absorbing in the UV in the gas phase nor from mercury compounds not fully reducible by tin(II) chloride alone; interferences from other elements depend on their concentrations — exceeding the values in Table 2 may cause negative bias: Cu(II) 500 mg/l, Ni(II) 500 mg/l, Ag(I) 1 mg/l in the test solution; heavy metals interfere less with tin(II) chloride than with borohydride, and in flow systems interferences may be smaller than in Table 2. Reagents (5): adequate purity for trace and ultra-trace determinations — mercury and interfering substances in reagents and water should be negligible compared with the lowest concentration determined; water of grade 2; carrier gas argon or nitrogen ≥ 99.99 %; HCl 12 mol/l and HNO3 15 mol/l — each from a single batch throughout; diluted HNO3 (10 ml in 1000 ml); HNO3 2 mol/l for rinsing glassware; diluted aqua regia (21 ml HCl and 7 ml HNO3 in 1000 ml); tin(II) chloride 100 g/l (10 g SnCl2·2H2O in 30 ml HCl, to 100 ml; the blank can be reduced by purging with nitrogen for 30 min; prepared on the day of use; in flow systems e.g. 0.5 g/100 ml); sodium borohydride 30 g/l in NaOH solution (in flow systems e.g. 3 g/l, fresh); mercury stock solution (1000 ± 2) mg/l (stable at least one year); standard solutions 100 mg/l (one month), 1 mg/l (7 days) and 100 µg/l (on the day of use), each with 10 ml HNO3 in 100 ml. Apparatus (6): glassware cleaned for trace determinations, e.g. at least 6 h in HNO3 2 mol/l (replaced weekly), then rinsed with water; atomic absorption spectrometer with a cold-vapour generation system and a quartz or glass cell, preferably with an electrodeless discharge lamp (greater, more stable intensity) or a hollow cathode lamp; background correction is recommended.

STATUS (as of 03.10.2026). The PKN search (query “PN-EN 16175-1”, 03.10.2026) returns one result: PN-EN 16175-1:2017-02 (English version, “Wprowadza: EN 16175-1:2016 [IDT]”) without a withdrawal note. In the iTeh catalogue (read on 03.10.2026) EN 16175-1:2016 has the status “Published”, stage 90.93 (decision to confirm the standard).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 03.10.2026). The number 16175-1 appears in 7 records at 3 laboratories: AB 213 (2), AB 216, AB 680 (4). In the current PCA documents (read on 03.10.2026, issues from 05.11.2025 to 17.04.2026) the number appears in 7 rows — 4 at AB 680, 2 at AB 213 and 1 at AB 216; in each of the three documents the number of page markers equals the number of PDF pages, without repetitions; a search of all 1291 PCA documents downloaded from BIP on 03.10.2026 found no laboratories outside the database copy (17 laboratories in the register have no link to a scope document on BIP). Form “PN-EN 16175-1:2017-02” at all — at AB 213 together with PN-EN 16174:2012 (aqua regia digestion), at AB 216 together with PN-EN ISO 54321:2021-07. None of these items is suspended. The “Laboratories” tab (query “PN-EN 16175-1”) shows all 3 laboratories — checked with a tab query on the labcoda.pl production server on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Characteristic at all: mercury content, CVAAS method. AB 680: soil (0.013–3.3) mg/kg; soil improvers, sewage sludge and wastes with codes 19 05 03 and 19 05 99 — each (0.013–33) mg/kg. AB 213: compost, biomass, stabilised material, sewage sludge (0.05–25.0) mg/kg; plant growing aids — soil improvers and growing media (0.05–3.0) mg/kg. AB 216: sewage sludge (0.1–50) mg/kg.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. At the solution: the standard concerns digests obtained according to EN 16173 or EN 16174 (1) — it does not itself describe digestion. At the range: the lower working range limit is 0.03 mg/kg dry matter (1) — the lower limit of AB 680 (0.013 mg/kg) lies below it; 1–10 µg/l (0.03–0.3 mg/kg with 3 g) is determined directly, higher after dilution (3). At the matrix: the scope is sludge, treated biowaste and soil (1) — waste (AB 680) is not in it. At the reductant: tin(II) chloride is recommended, because sodium borohydride reduces many other elements (3, 4). At interferences: Cu and Ni above 500 mg/l, Ag above 1 mg/l in the solution give low results (4, Table 2). At reagents: one batch of HCl and HNO3, tin(II) chloride and the most diluted standard on the day of use (5). At glassware: at least 6 h in 2 mol/l HNO3 (6.1).

WHAT WE DO NOT GIVE. We did not read the procedure, calibration, calculation, precision data or validation results (Annex A). We do not give permissible mercury contents in sludge, compost or soil.

Method principle

In the digest of sludge, biowaste or soil obtained with aqua regia or nitric acid, mono- and divalent mercury is reduced in acid medium with tin(II) chloride (recommended) or sodium borohydride to elemental mercury. A carrier gas (argon or nitrogen) strips the mercury vapour in a closed system into a quartz or glass cell in the light path of an atomic absorption spectrometer; the absorbance at 253.7 nm is converted to concentration using a calibration curve, and the result is given in mg/kg dry matter.

Applications

• Mercury in sewage sludge, treated biowaste and soil after digestion according to EN 16173 or EN 16174 — from 0.03 mg/kg dm (1)
• Validation: municipal sludge, compost, soil (Table 1)
• Soil, sewage sludge, compost, stabilised material, soil improvers, growing media and waste — items in the accreditation scopes of 3 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN 16175-1:2017-02

Title (PL)

Osady ściekowe, uzdatnione bioodpady oraz gleba — Oznaczanie zawartości rtęci — Część 1: Atomowa spektrometria absorpcyjna, technika zimnych par (CV-AAS)

Title (EN)

Sludge, treated biowaste and soil — Determination of mercury — Part 1: Cold-vapour atomic absorption spectrometry (CV-AAS)

Step-by-step procedure

1. Sample solution

   Digestion according to EN 16173 (HNO3) or EN 16174 (aqua regia), dry matter according to EN 15934 (1, 2). PN-EN 16175-1:2017-02 without a withdrawal note (03.10.2026).

2. Reagents and standards

   Tin(II) chloride and 100 µg/l standard fresh on the day of use; glassware after HNO3 bath (5, 6.1).

3. Reduction and stripping

   SnCl2 (or NaBH4) in acid medium, carrier gas in a closed system (3).

4. Measurement

   Absorbance at 253.7 nm; 1–10 µg/l directly, higher after dilution (3).

5. Result

   From the calibration curve, in mg/kg dry matter; check of Cu, Ni, Ag interferences (3, 4).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard does not address all safety issues — the user establishes safety practices; tests by trained staff (introduction)
• Mercury and its vapour are toxic — closed system, ventilation

Frequently asked questions