🌿 Digestion of soil, treated biowaste, sludge and waste prior to element determination — 0.2–0.5 g of dried and ground (below 250 µm) sample is digested with 6 ml HCl, 2 ml HNO3 and 4 ml HBF4 in a heating block for 2 h at (105 ± 5) °C (method A) or in a closed microwave vessel up to (175 ± 5) °C for 10 min (B1), or with an HCl, HNO3 and HF mixture with a power programme (B2); the decomposition is considered effectively total; 30 elements from Al to Zn, PN-EN 13656

Environment PN-EN 13656

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of SIST EN 13656:2020 (English text of EN 13656:2020): from the contents through the European foreword, the introduction with Table 1 and warnings and Clauses 1–7 to 8.4.1 (method B1, with the warning about too fast temperature increase) on page 10. Outside the sample remain the rest of method B1, method B2 (8.4.2), the test report (9), Annex A (normative, calibration of the power adjustment), Annexes B and C (repeatability and reproducibility data) and the bibliography.

ACCORDING TO THE TEXT OF EN 13656:2020. The standard was prepared by CEN/TC 444 “Environmental characterization of solid matrices”, whose secretariat is held by NEN; national implementation was due by May 2021 at the latest; the document superseded EN 13656:2002, adding HBF4 (preferred over HF for safety reasons), a heating block procedure and a temperature-controlled microwave procedure, and removing microwave digestion in semi-open vessels. According to the introduction, the methods provide multi-element digestion of soil, treated biowaste, sludge and waste; elements extractable by this procedure can in many instances be described as “total”, although this is sample dependent, but they cannot be regarded as available for leaching, as the procedure is too vigorous to represent natural processes. Table 1 — validation: with HCl:HNO3:HBF4 and with HCl:HNO3:HF — city waste incineration ash (BCR176/BCR176R), ink waste sludge (organic matrix), electronic industry sludge (“metallic” matrix); only with HBF4 — sediment; only with HF — coal fly ash, steel slag, copper slag, city waste incineration fly ash and bottom ash, sewage sludge (BCR 146R). Warnings: most reagents are extremely corrosive and very toxic, in addition to high temperature and pressure; laboratory-grade microwave equipment with isolated, corrosion-resistant safety devices is essential — domestic ovens should not be used, as acid vapours may compromise the safety devices and the magnetron may not shut off when the door is open; all procedures should be performed in a fume hood or closed force-ventilated equipment; with strong oxidisers explosive intermediates are possible, especially in samples with high organic content; pressurized vessels are not opened before cooling; tests are carried out by trained staff informed of the risks of HBF4 and HF. Scope (1): three methods for digesting soil, treated biowaste, sludge and waste with HCl, HNO3 and HBF4 or HCl, HNO3 and HF; digestion with these acids is effectively considered a total decomposition of the sample; elements: Al, Sb, As, Ba, Be, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Hg, Mo, Ni, P, K, Se, Ag, Na, Sr, S, Te, Tl, Sn, Ti, V and Zn; other elements — after the user has verified applicability. References (2): EN 15002, EN 15934, EN 16179. Terms (3): digestion, dry residue (105 °C), dry matter fraction, laboratory sample, sample, test portion, test sample. Principle (4): method A — heating block, HCl, HNO3 and HBF4, (105 ± 5) °C for 2 h; method B1 — temperature-controlled microwave to (175 ± 5) °C in a closed vessel, HCl, HNO3 and HBF4; method B2 — power-controlled microwave in a closed vessel, HCl, HNO3 and HF; then filtration or centrifugation; according to a note, temperature-controlled microwave digestion can also be used with HF after verification; for safety reasons HBF4 is strongly recommended over the much more hazardous HF. Interferences (5): the sample container can be a source of errors (e.g. elemental mercury penetrates polyethylene walls very rapidly, glass contributes Na, K, Al); grinding risks contamination, and elevated temperature losses of volatile elements (special care with Hg, As, Pb); filtration must not introduce contaminants; the whole test portion must contact the acids; some elements may precipitate as low-soluble chlorides, fluorides or sulphates; in microwaves the manufacturer’s upper test portion mass applies, reactive, volatile, carbonate or carbon-based materials may vent the vessel with loss of analytes, and the vessel is opened only after cooling. Reagents (6): acids of analytical grade or with verified content of the elements to be determined; a blank throughout the procedure; deionized water; HBF4 about 6 mol/l (38–48 %); HF about 23 mol/l (40–45 %); boric acid solid and solution about 4 %; HCl about 12 mol/l (35–37 %); HNO3 about 15 mol/l (65–70 %). Apparatus (7): glassware and plastics suitably cleaned; method A — 50 ml polypropylene tubes with polyethylene screw caps (tested for element release), heating block (105 ± 5) °C; method B — pressure vessels typically 100 ml, withstanding at least 3000 kPa, of modified PTFE with a safety relief system; temperature-controlled microwave system (control accuracy ± 5 °C, power adjustment within 2 s, sensors ± 2 °C, periodic check — re-calibration if deviation > 2 °C) or power-controlled (± 10 W, typically 600–1200 W, calibration according to Annex A), corrosion-resistant, ventilated, with temperature or pressure control; household instruments are not suitable; 0.45 µm filters; 50 or 100 ml flasks; balance 1 mg. Procedure (8): pretreatment of soil, sludge and biowaste according to EN 16179, waste according to EN 15002; dry matter according to EN 15934; pretreatment should include drying and grain size reduction below 250 µm (liquid samples — homogenization by high-speed mixer or sonication); representative test portion complying with the manufacturer’s specifications — a larger one is divided, digested separately and the digests combined; a blank in parallel, with acceptance limits defined by the laboratory. Method A (8.3): 0.2–0.5 g to 0.001 g; organic carbon at most 0.15 g per 8 ml HCl/HNO3, and per additional 0.1 g — 1 ml more HNO3; moistening with a few drops of water; (6.0 ± 0.1) ml HCl, (2.0 ± 0.1) ml HNO3, (4.0 ± 0.1) ml HBF4; standing until effervescence almost ceases; loosely capped tube in the block, slow heating to (105 ± 5) °C and 120 min; after cooling made up with water; a suspension may be centrifuged or filtered, but particles indicate incomplete digestion, which is stated in the report. Method B1 (8.4.1): the same masses and acid volumes in a microwave vessel; with a vigorous reaction, wait before capping; all carousel positions are filled (empty ones with acid mixture only) so that energy absorption is the same; the method is operationally defined; heating at about 10–15 °C/min to (175 ± 5) °C and (10 ± 1) min at that temperature, cooling; warning — a too high temperature increase may cause a vigorous exothermic reaction, pressure rise and valve blow-off with loss of analytes.

STATUS (as of 03.10.2026). The PKN search (query “PN-EN 13656”, 03.10.2026) shows PN-EN 13656:2021-05 (English version, “Wprowadza: EN 13656:2020 [IDT]”) without a withdrawal note, and the withdrawn PN-EN 13656:2006 (Polish version, replaced by PN-EN 13656:2021-05; it concerned microwave-assisted digestion of waste with HF, HNO3 and HCl) and PN-EN 13656:2003 (English version). In the iTeh catalogue (read on 03.10.2026) EN 13656:2020 has the status “Published”, stage 90.60 (close of systematic review enquiry).

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 13656 appears in 6 records at 3 laboratories: AB 550, AB 688 (4), AB 713. In the current PCA documents (read on 03.10.2026, issues from 30.03.2026 to 22.09.2026) the number appears in 6 rows — 4 at AB 688 and one at each of the others; 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). In all items PN-EN 13656 stands together with other documents: with PN-EN 13657:2006 and PN-EN ISO 11885:2009 (AB 688; in one item also with PN-EN 196-2:2013-11 clause 4.5.2), with PN-EN ISO 17294-2:2024-04 (AB 713) and without year with PN-EN ISO 11885, PN-ISO 11466 and PN-EN 13657 (AB 550); form “PN-EN 13656:2021-05” (AB 688, AB 713) or “PN-EN 13656” (AB 550). None of these items is suspended (the word “zawieszony” in the AB 550 document refers to suspended particulate matter). The “Laboratories” tab (query “PN-EN 13656”) 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). AB 688 (ICP-OES): hard coal — elements and oxides in ash (including Si/SiO2, Al/Al2O3, Fe/Fe2O3, Ca/CaO, Mg/MgO, Na/Na2O, K/K2O, P, Ti, As, B, Ba, Cd, Co, Cr, Cu, Mo, Mn, Ni, Pb, Sn, Sr, V); wastes with codes 17 01 01, 17 01 02, 17 01 03, 17 01 07, 17 05 04, 20 02 01 — oxides and major elements; wastes with codes from groups 10 01 and 19 09 and ashes, slags, ash–slag mixtures, ashes with desulphurisation products and fluidised-bed sands — oxides, major and trace elements; aggregates — oxides and major elements. AB 713 (ICP-MS): hard coal — V, Cr, Ni (0.500–250) mg/kg, Cu, Zn, Mn, Co, As, Sb, Cd (0.025–2.50) mg/kg, Hg and Tl (0.025–1.00) mg/kg, Pb. AB 550 (ICP-OES): soil, ground — element content, item in a flexible accreditation scope.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. At interpretation: the result is an effectively total content, not the fraction available for leaching (introduction, 1). At the elements: the list covers 30 elements, others only after verification (1) — silicon and boron (AB 688) are not on it. At the matrix: the scope is soil, biowaste, sludge and waste, validation according to Table 1 — hard coal and aggregates (AB 688, AB 713) are not listed, Table 1 includes coal fly ash. At the sample: drying and grinding below 250 µm, care with volatile Hg, As, Pb (5.1, 8.1). At organic matter: at most 0.15 g of organic carbon per 8 ml HCl/HNO3, more — additional HNO3 (8.3). At suspension: particles after digestion indicate incomplete decomposition and must be reported (8.3). At microwaves: full carousel, controlled heating rate, opening after cooling (5.2, 8.4.1). At acids: HBF4 instead of HF for safety reasons (4).

WHAT WE DO NOT GIVE. We did not read method B2, the power calibration (Annex A) or the precision data (Annexes B and C). We do not give the technique for determining the elements after digestion — the standard does not specify it.

Method principle

A dried and ground (< 250 µm) test portion of 0.2–0.5 g is digested with 6 ml HCl, 2 ml HNO3 and 4 ml HBF4 — in a heating block for 2 h at (105 ± 5) °C (A) or in a closed microwave vessel heated at 10–15 °C/min to (175 ± 5) °C and held 10 min (B1) — or with an HCl, HNO3 and HF mixture in a power-controlled microwave (B2). The solution is made up with water, centrifuged or filtered if necessary and passed on for element determination by any suitable technique; the decomposition is considered effectively total.

Applications

• Soil, treated biowaste, sludge and waste — digestion for determination of 30 elements (Al, Sb, As, Ba, Be, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Hg, Mo, Ni, P, K, Se, Ag, Na, Sr, S, Te, Tl, Sn, Ti, V, Zn) (1)
• Validated matrices: incineration ashes and slags, industrial sludges, sediment, coal fly ash, metallurgical slags, sewage sludge (Table 1)
• Hard coal, ashes, slags, construction waste, aggregates and soil — items in the accreditation scopes of 3 laboratories in PCA (always together with the standard of the determination technique)

Key parameters

Standard

Standard number

PN-EN 13656:2021-05

Title (PL)

Gleba, uzdatnione bioodpady, osady ściekowe oraz odpady — Roztwarzanie mieszaniną kwasów chlorowodorowego (HCl), azotowego(V) (HNO3) oraz tetrafluoroborowego (HBF4) lub hydrofluorowego (HF) do dalszego oznaczania pierwiastków

Title (EN)

Soil, treated biowaste, sludge and waste — Digestion with a hydrochloric (HCl), nitric (HNO3) and tetrafluoroboric (HBF4) or hydrofluoric (HF) acid mixture for subsequent determination of elements

Step-by-step procedure

1. Sample preparation

   EN 16179 (soil, sludge, biowaste) or EN 15002 (waste); drying, < 250 µm; dry matter according to EN 15934 (8.1). PN-EN 13656:2021-05 without a withdrawal note (03.10.2026).

2. Test portion and acids

   0.2–0.5 g, moistening with water, 6 ml HCl, 2 ml HNO3, 4 ml HBF4; wait until effervescence ceases (8.3, 8.4.1).

3. Digestion

   A: block 105 °C, 120 min; B1: microwave 10–15 °C/min to 175 °C, 10 min, full carousel (8.3, 8.4.1).

4. Measurement solution

   Cooling, making up with water, centrifugation or filtration if needed; particles = incomplete digestion, noted in the report (8.3).

5. Blank

   In parallel, same acids without sample; acceptance limits defined by the laboratory (8.2).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Most reagents are extremely corrosive and very toxic; in addition high temperature and pressure (introduction, warning)
• Laboratory microwave systems only — domestic ovens may not shut off the magnetron with the door open (introduction)
• Work in a fume hood; explosive intermediates possible with organic samples; open vessels after cooling (introduction, 5.2)
• HBF4 instead of the much more hazardous HF; staff trained in the hazards of both acids (4, introduction)

Frequently asked questions