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LabCoda / Knowledge Base / Heavy metals in soil (ICP-OES)

🌿 Heavy metals in soil (ICP-OES)

Environmental PN-EN ISO 11885

In short

Multi-element determination of heavy metals (Pb, Cd, Cr, Cu, Zn, Ni, As, Hg) in soil after acid digestion, by ICP-OES method. The test is performed according to PN-EN ISO 11885:2009; Linear range: 3–5 orders of magnitude. The procedure comprises 6 steps (about 1 days 1 h 43 min–1 days 1 h 45 min in total); it is used for: Assessment of soil contamination with heavy metals (2016 Polish regulation), Testing soils on post-industrial sites (brownfields), Environmental monitoring around industrial plants.

At a glance

  • Standard: PN-EN ISO 11885:2009
  • Category: Environmental
  • Procedure steps: 6
  • Total time of stages: 1 days 1 h 43 min–1 days 1 h 45 min
  • Determined elements: Pb, Cd, Cr, Cu, Zn, Ni, As, Hg, Co, Mn, Fe, V, Ba + others
  • Detection limit: 0.01–1 mg/kg d.m. (element-dependent)
  • Linear range: 3–5 orders of magnitude

Overview

Determination of heavy metals in soil is a key element of soil environment assessment. Metals such as lead, cadmium, chromium, copper, zinc, nickel, arsenic, and mercury accumulate in soil and do not biodegrade, posing a long-term threat to ecosystems, groundwater, and human health.

The 2016 Polish regulation on soil quality standards specifies permissible metal concentrations depending on soil group (I — residential areas, IV — industrial). E.g., lead: 100 mg/kg (gr. I) to 600 mg/kg (gr. IV), cadmium: 1 mg/kg (gr. I) to 15 mg/kg (gr. IV).

The method involves soil sample digestion with acid mixture (HNO₃ + HCl, i.e., aqua regia, or HNO₃ + HF + HClO₄) in microwave digester, followed by multi-element analysis of the solution by ICP-OES. In one analytical cycle, 20–30 elements are determined simultaneously.

THE STANDARD DESCRIBES MEASUREMENT IN SOLUTION, NOT EXTRACTION FROM SOIL — SUPPLEMENT (23.09.2026). The entry concerns metals in SOIL, while PN-EN ISO 11885, cited for it, bears the title "Jakość WODY — Oznaczanie wybranych pierwiastków metodą optycznej spektrometrii emisyjnej z plazmą indukcyjnie sprzężoną (ICP-OES)" [WATER quality — Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES)]. It is not, however, an inappropriate document: the standard describes the MEASUREMENT TECHNIQUE in solution and is cited for soil — out of 114 entries concerning metals in soil or ground it has 11 citations. THE DEFECT LIES IN INCOMPLETENESS, NOT IN THE SUBJECT: it describes how to measure the elements in a ready solution, not how to obtain that solution from the soil. WHAT LABORATORIES CITE FOR METALS IN SOIL (measurement on the scopes, 23.09.2026): PN-ISO 11047 — 14 citations, and it is a standard DIRECTLY on metals in soil extracts; PN-EN 12457 and PN-EN ISO 11885 — 11 each; PN-R-04016 and PN-R-04017 — 10 each; PN-ISO 11466 (aqua regia extraction) — 5. THAT IS WHY I REPEAT HERE A SENTENCE FROM THE ENTRY ON PN-ISO 11047, BECAUSE IT FITS WORD FOR WORD: A RESULT IN mg/kg WITHOUT THE METHOD OF EXTRACTION STATED MEANS NOTHING. The same soil sample subjected to aqua regia extraction and to extraction with a weaker reagent will give results that differ many times over, and both numbers will be correct for their own method.

Method principle

The soil sample is digested in closed PTFE vessels in a microwave digester with acid mixture (aqua regia: 3 vol. HCl + 1 vol. HNO₃ according to ISO 11466, or mixture with HF for complete dissolution of silicates). The digest is diluted with ultrapure water and analyzed on ICP-OES spectrometer. Argon plasma (6000–10000 K) atomizes and excites elements, which emit radiation at characteristic wavelengths. Detection on a CCD polychromator enables simultaneous measurement of many elements.

Applications

Key parameters

ParameterValue
Determined elementsPb, Cd, Cr, Cu, Zn, Ni, As, Hg, Co, Mn, Fe, V, Ba + others
Detection limit0.01–1 mg/kg d.m. (element-dependent)
Linear range3–5 orders of magnitude
Precision (CV)3–10%
DigestionAqua regia, 180°C, 30 min (microwave)

Standard

Standard number
PN-EN ISO 11885:2009
Title (PL)
Jakość wody — Oznaczanie wybranych pierwiastków metodą optycznej spektrometrii emisyjnej z plazmą indukcyjnie sprzężoną (ICP-OES)
Title (EN)
Water quality — Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES)

Step-by-step procedure

  1. Sample preparation

    Dry soil at 40°C. Sieve through 2 mm sieve, then grind <2 mm fraction to <0.25 mm. Weigh 0.5 g.

    ⏱ Time: 24 h • 🌡 Temperature: 40°C

  2. Microwave digestion

    Add 9 mL HCl + 3 mL HNO₃ (aqua regia). Program: ramp to 180°C/15 min, hold 20 min.

    ⏱ Time: 45 min • 🌡 Temperature: 180°C

  3. Filtration and dilution

    After cooling, transfer quantitatively to 50 mL flask. Fill to mark with ultrapure water. Filter (0.45 µm).

    ⏱ Time: 15 min

  4. ICP-OES calibration

    Prepare standards: 0, 0.1, 0.5, 1, 5, 10, 50 mg/L in 5% HNO₃. Calibrate instrument.

    ⏱ Time: 30 min

  5. Sample measurement

    Measure samples with blank and CRM every 10 samples. Check spike recovery (90–110%).

    ⏱ Time: 3–5 min/sample

  6. Calculations

    Convert concentrations to mg/kg dry mass of soil. Account for dilution and moisture.

    ⏱ Time: 10 min

Required equipment and apparatus

EquipmentExampleIndicative price
ICP-OES spectrometerThermo iCAP 7400, Agilent 5800, PerkinElmer Avio 220350,000–700,000 PLN
Microwave digesterAnton Paar Multiwave 5000, CEM Mars 6, Milestone Ethos UP150,000–300,000 PLN
AutosamplerThermo ASX-560, Agilent SPS 425,000–60,000 PLN
Analytical balanceMettler Toledo ME204, 0.1 mg accuracy5,000–15,000 PLN
PTFE digestion vessels100 mL vessels, set of 6–12 pcs.500–2,000 PLN/pc.

Reagents, media and consumables

ReagentCASDetails
Nitric acid 65% suprapur7697-37-2Trace analysis grade
Hydrochloric acid 30% suprapur7647-01-0Aqua regia component
Multi-element standard solutions—ICP Multi-Element Standard IV, 1000 mg/L, certified CRM
Argon 5.07440-37-1Plasma gas, 99.999% purity
Ultrapure water—Resistivity >18.2 MΩ·cm

Health and safety (OHS)

Frequently asked questions

Which standard describes this test?

The test is performed according to PN-EN ISO 11885:2009 — “Water quality — Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES)”.

How does this method work?

The soil sample is digested in closed PTFE vessels in a microwave digester with acid mixture (aqua regia: 3 vol. HCl + 1 vol.

What is the measuring range and accuracy?

Determined elements: Pb, Cd, Cr, Cu, Zn, Ni, As, Hg, Co, Mn, Fe, V, Ba + others; Detection limit: 0.01–1 mg/kg d.m. (element-dependent); Linear range: 3–5 orders of magnitude; Precision (CV): 3–10%.

How long does the test take?

The times given for the individual stages add up to approximately 1 days 1 h 43 min–1 days 1 h 45 min. The procedure comprises 6 steps.

What equipment is required?

ICP-OES spectrometer, Microwave digester, Autosampler, Analytical balance, PTFE digestion vessels. Indicative cost of the core instrument (ICP-OES spectrometer): 350,000–700,000 PLN.

Where is this test used?

Assessment of soil contamination with heavy metals (2016 Polish regulation); Testing soils on post-industrial sites (brownfields); Environmental monitoring around industrial plants; Agricultural soil quality assessment; Control of sewage sludge used in agriculture; Soil remediation — effectiveness verification.

What safety precautions apply?

Aqua regia — highly corrosive, releases chlorine. Work in fume hood.; HF (if used) — extremely dangerous, causes deep burns and hypocalcemia; Microwave digester — pressure up to 40 bar, follow safety procedures; Acid-resistant gloves, apron, safety goggles mandatory; Acid waste with metals — collect separately.

Which laboratory can perform this test?

The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 11885.

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