Overview
ISO 20280:2007 - "Soil quality - Determination of arsenic, antimony and selenium in aqua regia soil extracts with electrothermal or hydride‑generation atomic absorption spectrometry" - specifies laboratory methods to measure As, Sb and Se in soil extracts prepared with aqua regia (ISO 11466). The standard covers two instrumental approaches: electrothermal atomic absorption spectrometry (ETAAS) and hydride‑generation atomic absorption spectrometry (HGAAS), including calibration, sample preparation, reagents and measurement conditions.
Key topics and requirements
- Scope and principle: Extraction of trace elements from soil using aqua regia (ISO 11466) followed by determination by ETAAS or HGAAS.
- Methods:
- Method A (ETAAS) - discrete sample introduction into a graphite tube with stepwise temperature programme; background correction (preferably Zeeman) recommended.
- Method B (HGAAS) - chemical pre‑reduction of species and hydride formation (NaBH4) with transport to a heated quartz cell (≈900 °C) for decomposition and measurement.
- Reagents and modifiers: aqua regia, concentrated/diluted HCl and HNO3, palladium/magnesium nitrate modifier for ETAAS, pre‑reduction solution (ascorbic acid + KI) for As and Sb, hydrochloric pre‑reduction for Se, sodium borohydride for hydride generation.
- Calibration and measurement: preparation of stock and working standards (1 000, 100 and 1 mg/l examples), plotting calibration graphs and options for standard additions. Measurement wavelengths specified: As 193.7 nm, Sb 217.6 nm, Se 196.0 nm.
- Quality and safety: use of high‑purity reagents and Grade 2 water (ISO 3696); strict safety handling for concentrated acids, toxic element solutions and waste disposal.
Applications and users
ISO 20280:2007 is designed for:
- Environmental and soil testing laboratories performing trace metal analysis.
- Regulatory agencies and consultants monitoring soil contamination and remediation projects.
- Research groups studying geochemistry, pollution pathways or soil quality.
Practical uses include baseline soil surveys, contamination assessment, compliance testing and support for remediation decisions where accurate determination of arsenic, antimony and selenium is required.
Related standards
- ISO 11466 - Extraction of trace elements soluble in aqua regia (referenced for sample extraction).
- ISO 11464, ISO 11465 - Sample pretreatment and dry matter determination for soil quality.
- ISO 3696 - Water for analytical laboratory use (Grade 2).
Safety note: ISO 20280 emphasizes handling toxic elements and concentrated acids with appropriate laboratory controls and waste‑management procedures.