🌿 Eight metals in aqua regia extracts of soil — FAAS and ETAAS, PN-ISO 11047

Environment PN-ISO 11047

Overview

WHAT THIS STANDARD DESCRIBES. The scope from the PKN catalogue card: "Podano oznaczanie kadmu, chromu, kobaltu, miedzi, ołowiu, manganu, niklu i cynku, w ekstraktach gleby kwasami (wodą królewską wg PN-ISO 11466), metodami płomieniowej AAS i kuwety grafitowej AAS (elektrotermiczną)" [The determination of cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc in acid extracts of soil (aqua regia according to PN-ISO 11466) by flame AAS and graphite furnace AAS (electrothermal) is given]. The standard was published on 6 November 2001 in a Polish-language version, has 24 pages, is maintained by KT 191 Soil Chemistry and implements ISO 11047:1998 with the degree [IDT], i.e. as an identical text. The card has no "Replaces" field, nor does it have a "Withdrawn" header or a "Withdrawal date" row (checked on 23.09.2026).

TWO STANDARDS MAKE UP ONE DETERMINATION — AND THEY MUST BE READ TOGETHER. This standard describes only the MEASUREMENT in the finished extract; the extraction itself is carried out according to PN-ISO 11466, to which the card refers directly. A laboratory that has only one of them in its scope performs half of the procedure — and this can be seen in the accreditation scopes, where the two standards usually stand in the same row. **The result of the determination depends on the extraction at least as much as on the measurement**: aqua regia does not dissolve silicates, so what is obtained is the content "available in aqua regia", not the total content of the element in the soil. The report must name both standards, because a number in mg/kg alone, without stating the extraction method, means nothing.

EIGHT METALS IN THE STANDARD, SIX IN THE SCOPES — A MEASUREMENT THAT SHOWS IT. The title of the standard lists eight elements. In accreditation scopes the laboratories citing this standard usually list six: cadmium, chromium, copper, nickel, lead and zinc. **Cobalt appears at two laboratories, manganese at three** — out of seventeen citing the standard (reading of 23.09.2026). The reason is practical, not technical: the regulations on the assessment of soil contamination list precisely these six among the heavy metals, while cobalt and manganese have no limit values in them. **The standard therefore describes more than is accredited in practice** — and a reader of a scope who sees a citation of PN-ISO 11047 cannot infer from it that the laboratory determines all eight metals.

TWO TECHNIQUES IN ONE STANDARD — AND THE CHOICE IS THE LABORATORY'S. The standard allows flame atomic absorption spectrometry (FAAS) and electrothermal spectrometry with a graphite furnace (ETAAS). The difference concerns the measuring range: FAAS is sufficient for copper, zinc, manganese and chromium, whose contents in soils reach hundreds of mg/kg, while ETAAS is needed for cadmium and lead at low contents. This can be seen directly in the scopes — the same laboratory gives different lower limits for different elements under this standard, for example cadmium from 0.80 mg/kg and zinc from 5.00 mg/kg. **A citation of the standard without stating the technique therefore does not say how low the laboratory goes.**

SCALE OF CITATIONS (reading of 23.09.2026, copy of the database of accreditation scopes). Matching by the BEGINNING of the notation, i.e. the way the "Laboratories" tab searches: 22 entries at 16 laboratories; across all forms of the core "11047" — 23 at 17. Seven forms of notation, the balance of occurrences agrees: "PN-ISO 11047:2001" 16 times, "PN-ISO 11047:2001 Metoda A" [Method A] 2, "PN-ISO 11047: 2001" with a space after the colon 1, "PN-ISO 11047:2001 met. A" 1 and — this is the cause of the difference between the two numbers — **"P N-ISO 11047 4) I-01/1 5)" with a spaced-out PN element**, at AB 868.

THIS IS THE SEVENTH SAMPLE OF THE SAME PHENOMENON IN THIS DATABASE. Laboratory AB 868 wrote the standard with a split "P N" and with footnote references woven into the designation; no prefix will cover this, so for this standard it is invisible to the search engine. The scale of the phenomenon in this database: **194 laboratories have in their scope a standard under which the search engine will not find them**. Incidentally, this shows where some of these notations come from — not from carelessness, but from copying the text from the scope table together with the footnote numbers, which stand in superscript in the PDF and after conversion end up in one string with the designation.

TWO NOTATIONS WITH "METODA A" — WHAT WE DO NOT KNOW. Two laboratories add "Metoda A" [Method A] to the designation, one "met. A". The standard describes two techniques (FAAS and ETAAS) and we do not have its text, so WE DO NOT STATE which of them the designation "A" corresponds to — that would be guessing. We record only the fact: three laboratories out of seventeen mark a variant of the method in their scope, and fourteen do not.

Method principle

The soil sample is extracted with aqua regia according to PN-ISO 11466 — the mixture of concentrated hydrochloric and nitric(V) acids dissolves the sulphides, oxides, carbonates and organic compounds of the metals, but does NOT dissolve silicates. The resulting extract is diluted and introduced into an atomic absorption spectrometer: into an acetylene–air flame (FAAS) at higher contents or into a graphite furnace (ETAAS) at lower ones. The absorbance is measured at the resonance line appropriate for each element, and the content is read from the calibration curve and converted to the dry mass of the sample. The result is the content AVAILABLE IN AQUA REGIA, not the total content.

Applications

• Testing of soil contamination with heavy metals for the purposes of environmental assessment and administrative proceedings
• Assessment of soils intended for cultivation and checking of reclaimed land
• Testing of ground before construction investments — assessment of the need to replace the soil
• Monitoring of landfills and post-industrial sites

Key parameters

Standard

Standard number

PN-ISO 11047:2001 (wersja polska; wprowadza ISO 11047:1998 [IDT])

Title (PL)

Jakość gleby -- Oznaczanie kadmu, chromu, kobaltu, miedzi, ołowiu, manganu, niklu i cynku w ekstraktach gleby wodą królewską -- Metody płomieniowej i elektrotermicznej absorpcyjnej spektrometrii atomowej

Title (EN)

Soil quality — Determination of cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc in aqua regia extracts of soil — Flame and electrothermal atomic absorption spectrometric methods

Step-by-step procedure

1. Sample preparation

   Air-dry the soil sample, grind it and sieve it through a sieve with 2 mm mesh; weigh out a test portion for digestion.

2. Aqua regia extraction

   Carry out the extraction according to PN-ISO 11466 — this is a SEPARATE standard without which the determination is incomplete.

3. Preparation of the solution

   Filter the extract and make up to a known volume.

4. Choice of technique

   For each element choose FAAS or ETAAS depending on the expected content and the required lower limit of determination.

5. Measurement

   Measure the absorbance at the resonance line of the element; read the content from the calibration curve.

6. Calculation and report

   Convert to the dry mass of the sample. In the report state BOTH standards — extraction and determination — and indicate that the result is the content available in aqua regia, not the total content of the element in the soil.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Aqua regia is strongly corrosive and releases nitrosyl vapours — carry out the digestion in a properly functioning fume hood, wearing chemically resistant gloves and a face shield
• Microwave digestion: open the pressure vessels only after they have cooled down, in accordance with the instrument's instructions
• Cadmium and lead standard solutions are toxic — collect the waste separately as hazardous

Frequently asked questions