🌿 Available copper in mineral soil — colorimetry with "dwukupral" or flame AAS at 324.8 nm, PN-R-04017

Environment PN-R-04017

Overview

WHAT THE STANDARD COVERS. The scope from the PKN catalogue card, quoted in full: "Two kinds of methods are described: a colorimetric method with dwukupral and an atomic absorption spectrometry method. The colorimetric method consists in spectrophotometric measurement of the intensity of the yellow colour of the copper compound formed by the reaction of copper with dwukupral in an alcoholic solution in an acidic medium. The second method consists in selective absorption, by copper atoms, of radiation of wavelength 324.8 nm emitted by a copper cathode lamp." ("Dwukupral" is the reagent name as given on the card.) The card does not say what the soil extract is prepared with, nor whether the assessment table is in this standard — the second source quotes the table for copper with the note "PKN, 1992".

STATUS (state of the card on 28 September 2026). The card carries the heading "Withdrawn" and the row "Date of withdrawal: 15-11-2012". There are no "Superseded by" and "Supersedes" fields. Edition: published 30-06-1992, 4 pages, PKN technical committee KT 90 (Soil Cultivation and Horticulture), ICS 13.080.10. The PKN search (29 September 2026) for "przyswajalnej" (available, feminine form) shows only this standard, and for "przyswajalnego" only standards of the same series (PN-R-04016 … PN-R-04025 of 1992–1997 and two amendments to them) — a successor WE HAVE NOT ESTABLISHED. A regulation citing this standard as a test method WE HAVE NOT ESTABLISHED.

EXTRACT AND TECHNIQUE — ACCORDING TO A PUBLICATION OF THE NATIONAL AGRICULTURAL CHEMISTRY STATION. W. Lipiński, "Zasobność gleb Polski w mikroelementy" (Micronutrient status of Polish soils), Studia i Raporty IUNG-PIB 34(8), 2013: in the agricultural chemistry stations copper in mineral soils is determined after extraction with 1 mol/dm³ hydrochloric acid, by AAS; in 1965–1983 it was extracted according to Westerhoff with 0.43 N nitric acid and determined colorimetrically. The common 1 mol/dm³ HCl solution for copper, zinc, manganese and iron was introduced in 1986. "Available" means here: passing into this extract — not the total copper content of the soil.

CONTENT ASSESSMENT — THE TABLE FROM THE STANDARD. KSChR publication, Table 4 ("Source: PKN, 1992"), mg of copper per kg of soil: very light — low below 0.9, medium 0.9–2.5, high above 2.5; light — below 1.6, 1.6–4.9, above 4.9; medium — below 2.3, 2.3–6.7, above 6.7; heavy — below 5.0, 5.0–15.0, above 15.0. In 2009–2012, according to this assessment, 34 % of the soils tested by the stations had a low content, 57 % a medium and 9 % a high content (Table 9 of the publication). In 2013 the author writes (p. 122): "The currently applicable limit values used to evaluate soils for their micronutrient content are presented in Tables 1–7 (…)" (our translation); whether the stations apply them today — WE HAVE NOT ESTABLISHED. For organic soils the same publication gives a different extract (0.5 mol/dm³ HCl) and different limits: low below 6.0, medium 6.0–12.0, high above 12.0 mg/kg.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17 September 2026, read on 28 September 2026). All records of number R-04017: 16 entries at 16 laboratories — the same ones that cite the standards on available zinc, manganese and iron. Forms: "PN-R-04017:1992" — 10 laboratories; "PN-92/R-04017" — 6 (AB 317, AB 333, AB 759, AB 789, AB 798, AB 921). The "Laboratories" tab searches for records BEGINNING with "PN-R-04017" and will show 10 laboratories; it will not show the six with the form "PN-92/R-04017". All record the same technique: flame atomic absorption spectrometry (FAAS). None records the colorimetric method with dwukupral. AB 317 covers "mineral and organic soils" with this standard and cites its own instruction next to it (IB.19 of 4 April 2017). Current scopes on the PCA website (read on 29 September 2026): all 16 entries stand in the valid issues with the same range as in the copy, and none is suspended.

CLAUSES OF THE STANDARD IN THE SCOPES — A TRACE OF THE TWO METHODS. Laboratories using FAAS cite clauses 1, 2 and 4 (AB 312, AB 317, AB 921) or clause 4 alone (AB 1172), and exclude clause 3 (AB 759; AB 787 — "clauses 3 and 4.8"). In line with the order on the card this looks like a division: clause 3 — the colorimetric method, clause 4 — AAS; we did not have the text of the standard, so this is a conclusion from the records, not a quotation. Exception: AB 930 cites "clauses 1, 2, 3" with the FAAS technique. AB 333 excludes "clause 3.5" — just as in the standards on zinc, manganese and iron. What clauses 3.5 and 4.8 contain — WE HAVE NOT ESTABLISHED.

RANGES AND CLASS LIMITS — A PLACE FOR A RESULT THAT CANNOT BE CLASSIFIED. Ten laboratories start their range above 0.9 mg/kg — the low-content limit in very light soil: AB 284, AB 312, AB 317, AB 759, AB 779, AB 787, AB 1172, AB 1186 (from 1.0), AB 921 (from 1.2) and AB 930 (from 3.0); AB 930 also above the limits for light (1.6) and medium (2.3) soil. At 0.9 mg/kg or lower start AB 333 (0.75), AB 798 and AB 823 (0.5), AB 789 (0.6), AB 277 (0.8) and AB 827 (0.9). At the top, AB 277 and AB 1172 end their range at 10.0 mg/kg — below 15.0 mg/kg, the high-content limit in heavy soil; AB 921 ends at 16. A result outside the range for such a soil does not decide the class.

WHAT WE DO NOT GIVE. We did not have the text of the standard — PKN sells it (4 pages). We do not give the sample mass, the extraction conditions, the composition of the dwukupral solution and the wavelength of the colorimetric measurement, the calibration curve, the formula or the precision.

Method principle

According to the card of the standard, copper is determined by one of two methods: colorimetrically — measuring with a spectrophotometer the yellow colour of the copper compound with dwukupral in an alcoholic solution in an acidic medium — or by atomic absorption spectrometry, in which copper atoms absorb 324.8 nm radiation from a copper cathode lamp. According to the KSChR publication (2013), in the agricultural chemistry stations the mineral-soil extract is prepared with 1 mol/dm³ hydrochloric acid and copper is determined by AAS. The result in mg/kg is assessed with a table of classes for four soil texture categories. We DO NOT GIVE the extraction conditions — we did not have the text of the standard.

Applications

• Assessment of the available-copper status of mineral soils for fertiliser advice — in accreditation scopes exclusively agricultural soil-testing stations (16 laboratories), all by AAS
• Assessment according to the table of classes: the limits depend on the soil texture category (from 0.9 to 15.0 mg/kg)
• Not for organic soils: the KSChR publication gives for them a 0.5 mol/dm³ HCl extract and limits of 6.0 and 12.0 mg/kg; AB 317 also covers organic soils with this standard

Key parameters

Standard

Standard number

PN-R-04017:1992 (wersja polska)

Title (PL)

Analiza chemiczno-rolnicza gleby — Oznaczanie zawartości przyswajalnej miedzi

Title (EN)

Agricultural chemical analysis of soil — Determination of available copper content

Step-by-step procedure

1. Status of the document

   PKN card: standard withdrawn on 15-11-2012, no successor indicated (state of the card on 28 September 2026). In the report the full designation with the year and the method are given: PN-R-04017:1992, AAS or colorimetric.

2. Extract

   Mineral soil is extracted with 1 mol/dm³ hydrochloric acid (according to the KSChR publication). Sample mass and conditions NOT GIVEN.

3. Measurement — AAS variant

   Copper is determined in the extract by atomic absorption spectrometry at 324.8 nm, with a copper cathode lamp.

4. Measurement — colorimetric variant

   Copper is converted into the yellow compound with dwukupral in alcoholic solution in an acidic medium, and the colour intensity is measured with a spectrophotometer. No laboratory records this variant in its accreditation scope.

5. Result and assessment

   The copper content in mg/kg is assessed with the table for the soil texture category. A result below the range of a laboratory starting at 1.0 mg/kg does not decide the class of very light soil (limit 0.9 mg/kg).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Hydrochloric acid is corrosive — work with gloves and goggles, in a fume cupboard; its safety data sheet applies
• The colorimetric method requires an alcoholic solution — flammable; the safety data sheets of the reagents used apply
• TECHNICAL NOTE: the content class depends on the soil texture category — the report must state the category; without it the result in mg/kg gives no assessment

Frequently asked questions