🌿 Determination of major elements (Al, Ca, Fe, Mg, P, K, Si, Na, Ti) in solid biofuels — digestion in a closed vessel with a mixture of nitric acid, hydrogen peroxide and hydrofluoric acid at 220 °C (oven) or 190 °C (microwave), neutralisation of HF with boric acid, directly on the fuel (part A, 500 mg) or on ash prepared at 550 °C (part B, 50 mg), measurement by ICP-OES, ICP-MS, FAAS or FES, PN-EN ISO 16967

Environment PN-EN ISO 16967

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 16967:2015-06 (English version), in full (our translation): “This standard describes methods for the determination of major elements in solid biofuels, respectively of their ashes, such as Al, Ca, Fe, Mg, P, K, Si, Na, Ti. The determination of other elements such as barium (Ba) and manganese (Mn) is also possible with the methods described in this International Standard. This International Standard includes two parts. Part A describes the direct determination of elements in the fuel. This method is also applicable for sulfur and trace elements. Part B gives a method for the determination of elements in ash obtained at 550 °C”. We read the text of the standard in two iTeh samples: ISO 16967:2015 (English) — from the title page through the foreword, introduction and Clauses 1–8 up to and including 9.1.2 (digestion in parts A and B); SIST EN ISO 16967:2015 (text of EN ISO 16967:2015) — title pages and the European foreword. Outside the samples remain 9.2–9.5 (detection techniques, calibration, analysis of digests, blank test), Clauses 10 (calculations) and 11 (performance characteristics), the test report and Annexes A (conversion factors) and B (precision data).

ACCORDING TO THE TEXT OF ISO 16967:2015 (Clauses 1–8, 9.1.1–9.1.2). The standard was prepared by ISO/TC 238 “Solid biofuels”; CEN approved EN ISO 16967:2015 on 28 February 2015, and it replaced EN 15290:2011. Introduction: the elements described as major elements of solid biofuels are in fact major elements of the ashes; their determination serves to assess ash behaviour in a thermal conversion process or the use of ashes, high values of certain elements indicate fuel contamination or process additives, and high values of several elements together — contamination with sand or soil; the standard describes wet chemical methods. Scope (1): Al, Ca, Fe, Mg, P, K, Si, Na, Ti, also Ba and Mn; part A — directly on the fuel, also applicable to sulfur and trace elements; part B — on ash prepared at 550 °C. Principle (5): digestion in a closed vessel (reagents, temperature, pressure), detection by ICP-OES, ICP-MS, FAAS or FES. Reagents (6): water with negligible content of major elements (normally deionised), nitric acid ≥ 65 % (ρ = 1.41 g/ml), hydrogen peroxide 30 % (ρ = 1.11 g/ml), hydrofluoric acid 40 % (ρ = 1.13 g/ml) — with a warning of health hazard, boric acid 4 %; the accuracy of calibration is checked with certified reference materials, e.g. NBS 1570 (spinach leaves), NBS 1571 (orchard leaves), NBS 1573 (tomato leaves), NBS 1575 (pine needles); when recoveries are poor because of matrix effects, calibration is made with at least two CRMs and other ones are used for verification. Apparatus (7): oven or heating block to at least 220 °C with an accuracy of ± 10 °C, laboratory microwave oven with temperature control, vessels usually of fluoroplastic, balance 1 mg (part A) and 0.1 mg (part B), plastic volumetric flasks. Sample (8): general analysis sample with a nominal top size of 1 mm or less, prepared according to EN 14780 (to be replaced by ISO 14780); moisture according to ISO 18134-3. Part A (9.1.1): 500 mg of sample (to the nearest 1 mg) with 3.0 ml H2O2 (30 %), 8.0 ml HNO3 (65 %) and 1.0 ml HF (40 %) — with expected ash above 10 % 2.0 ml HF; at least 5 min reaction before closing the vessel, because closing too early raises the pressure rapidly, sometimes above the vessel limit; resistance heating — 1 h to 220 °C and 1 h at 220 °C (temperature of the device), microwave — 15 min to 190 °C and 20 min at 190 °C (temperature of the solution); if the relief valve opens, the digest is discarded because silicon may have escaped as gaseous SiF4; fluoropolymer vessels that cannot withstand more than 170 °C may be used with longer heating if results are comparable (e.g. on biomass reference materials); after cooling HF is neutralised with 10 ml H3BO3 (4 %) (with 2.0 ml HF — 20 ml) and heated again: resistance heating rapidly to 180 °C and 15 min, microwave rapidly to 150 °C and 15 min; the digest is transferred to a flask and made up with water depending on the measurement technique. Part B (9.1.2): ash according to ISO 18122, but only in platinum or graphite crucibles (larger ones allowed), without combustion aids and without refilling sample on the ash; the percentage of the prepared ash is compared with the ash determined exactly according to ISO 18122, and with a known ash content the results are converted to the fuel; the ash is homogenised in an agate mortar and re-ignited 30 min at 550 °C, and the portion is weighed immediately; 50 mg of ash (to the nearest 0.1 mg) with 2.0 ml H2O2, 3.0 ml HNO3 and 2.0 ml HF, the same heating programmes and the same rule of discarding after the valve opens; neutralisation with 20 ml H3BO3 and 10 ml water — the water keeps potassium in solution with ashes rich in KCl.

STATUS (card as of 03.10.2026). The card of PN-EN ISO 16967:2015-06 (English version, published 10-06-2015, 26 pages, price group M) has no “Withdrawn” header: Mining Sector, KT 144 Coke and Processed Solid Fuels, ICS 75.160.40, “Introduces: EN ISO 16967:2015 [IDT], ISO 16967:2015 [IDT]”, “Replaces: PN-EN 15290:2011 — English version”. There is no Polish language version in the PKN search engine (term “PN-EN ISO 16967”, 03.10.2026); the results also show PN-EN 16967:2017-08 — a different standard with the same number without “ISO”. In the iTeh catalogue (read on 03.10.2026) ISO 16967:2015 has the status “Published” and stage 90.92 “International Standard to be revised” (completed 29.08.2026) — ISO has decided to revise the standard; there is no new edition yet. Trace elements in biofuels are described in a separate entry on PN-EN ISO 16968 (shown under its Polish name “Oznaczanie pierwiastków śladowych w biopaliwach stałych (PN-EN ISO 16968)”) — AB 300 and AB 688 cite that standard together with this one.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read on 03.10.2026). The number 16967 with the prefix “PN-EN ISO” appears in 10 records at 5 laboratories: AB 300, AB 688, AB 713, AB 949, AB 981. In the current PCA documents (read on 03.10.2026, issues from 29.11.2024 to 09.09.2026) the number appears in 8 items of the same 5 laboratories (AB 300 — 3, AB 688 — 2, the others 1 each). Notation everywhere “PN-EN ISO 16967:2015-06”, with a note of the method: “met. A” or “met. B” (AB 300), “Metoda A” (AB 981). The “Laboratories” tab (“PN-EN ISO 16967”) shows the same 5 laboratories — checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Solid biomass — solid biofuel at all five laboratories. AB 688 — metals and oxides in biomass ash by ICP-OES (e.g. Al (0.030–4.7) %, Ca (0.50–35.0) %, K (0.060–28.0) %, Na (0.002–7.60) %) and silicon in biomass (Si (0.01–45.0) %, SiO2 (0.02–96.3) %) and silicon in ash by calculation. AB 949 — elements in biomass ash with conversion to oxides (e.g. Al (0.002–15.0) %, Ca (0.2–35.0) %). AB 713 — Na, K, P and Ca and their oxides, ICP-OES. AB 981 — potassium (0.10–30) g/kg and sodium (0.080–3.6) g/kg by method A, ICP-OES. AB 300 — aggregates, solid recovered fuel (SRF), biomass and waste with codes from the catalogue: by method B (samples after ashing) Si, Al, Fe, Ca, Mg, Ti, Mn, Na, K, Sr, Ba and As, Sb, P, Rb, Be, Tl, Li, S, Cd, Co, Cr and others, and by method A among others Ba, Ag, Zn, Cd, Co, Cr, Cu, Ni, Pb, V, Sn, Mo from 0.8 mg/kg — together with PN-EN ISO 16968. Aggregates, secondary fuels and waste lie outside the scope of the standard (solid biofuels), and trace elements by method B — outside the description of part B in Clause 1 (the standard assigns trace elements to part A). At AB 949 the footnote on suspension of part of the scope from 09.09.2026 concerns other items.

WHERE A SEEMINGLY CORRECT RESULT IS EASY. In digestion: closing the vessel before 5 min have passed may cause overpressure; when the valve opens, silicon escapes as SiF4 and the Si result is too low with no trace in the solution — the standard requires such a digest to be discarded (9.1.1). Too little HF with fuel of ash above 10 % does not decompose the silicates completely. In neutralisation: ash rich in KCl without the additional 10 ml of water loses potassium from the solution (9.1.2, note 2). With ash (part B): a different temperature, time, air flow, a crucible other than platinum or graphite, combustion aids or refilling the sample change the result — that is why the percentage of the prepared ash is compared with the determination according to ISO 18122; the ash portion is weighed right after ignition. In interpretation: the part B result refers to the ash — comparison with the fuel requires conversion via the ash content.

WHAT WE DO NOT GIVE. We have not read 9.2–9.5, Clauses 10–11 or the annexes, so we do not give the wavelengths and measurement conditions, the calibration, the final volume of the solution, the calculation formulas, the conversion to oxides (Annex A) or precision data. Nor do we say what the revision of ISO 16967 will change — there is no draft of it in the sources read.

Method principle

A sample of biofuel (part A, 500 mg) or of ash prepared at 550 °C (part B, 50 mg) is digested in a closed fluoroplastic vessel with a mixture of hydrogen peroxide, nitric acid and hydrofluoric acid, heated by resistance to 220 °C or by microwave to 190 °C; HF decomposes silicates. After cooling, excess HF is bound with boric acid and heated again, and the solution is made up with water and measured by ICP-OES, ICP-MS, FAAS or FES.

Applications

• Solid biofuels — Al, Ca, Fe, Mg, P, K, Si, Na, Ti, also Ba and Mn (1)
• Part A — directly on the fuel, also sulfur and trace elements; part B — on ash prepared at 550 °C (1)
• Assessment of ash behaviour in the boiler, use of ash, detection of fuel contamination with sand or soil (introduction)
• Solid biomass (at all five laboratories), and at one also aggregates, secondary fuels and waste — in the accreditation scopes of 5 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN ISO 16967:2015-06

Title (PL)

Biopaliwa stałe — Oznaczanie pierwiastków głównych — Al, Ca, Fe, Mg, P, K, Si, Na i Ti

Title (EN)

Solid biofuels — Determination of major elements — Al, Ca, Fe, Mg, P, K, Si, Na and Ti

Step-by-step procedure

1. General analysis sample

   Top size 1 mm or less, preparation according to EN 14780; determine moisture. PN-EN ISO 16967:2015-06 current (PKN card as of 03.10.2026).

2. Part A — digestion of the fuel

   500 mg + 3.0 ml H2O2, 8.0 ml HNO3, 1.0 ml HF (2.0 ml with ash > 10 %); at least 5 min before closing; 220 °C (resistance) or 190 °C (microwave).

3. Part B — ash and digestion

   Ash according to ISO 18122 in a Pt or graphite crucible, without additives; homogenisation, 30 min at 550 °C; 50 mg + 2.0 ml H2O2, 3.0 ml HNO3, 2.0 ml HF.

4. Neutralisation and solution

   Boric acid (10 ml or 20 ml; in part B 20 ml and 10 ml water), reheating; discard the digest if the valve opened; transfer to a flask and make up with water.

5. Measurement

   ICP-OES, ICP-MS, FAAS or FES; check with certified reference materials. We do not give the measurement conditions and calculations (9.2–10).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Hydrofluoric acid can seriously damage health (warning in 6.4) — work with suitable gloves and in a fume hood
• Closing the vessel too early or heating too fast raises the pressure rapidly, sometimes above the vessel limit (9.1.1)
• Hot concentrated acids and hydrogen peroxide — open vessels only after cooling to room temperature

Frequently asked questions