Overview
ISO 23161:2018 - "Soil quality - Determination of selected organotin compounds - Gas‑chromatographic method" - defines a validated gas‑chromatographic procedure for identifying and quantifying selected organotin compounds (OTCs) in soils. The standard is also applicable to sediments, sludges and wastes (soil‑like materials). It covers sample pretreatment, extraction, in‑situ derivatization, clean‑up, chromatographic separation and detection. The typical limit of quantification (LOQ) for each compound is about 10 µg/kg, while the working range depends on the detection technique and sample mass.
Key topics and technical requirements
- Target analytes: mono‑, di‑ and tri‑substituted organotin cations and selected peralkylated compounds - e.g. MBT (monobutyltin), DBT (dibutyltin), TBT (tributyltin), MOT, DOT, TPhT, TCyT and TTBT (tetrabutyltin).
- Sample pretreatment:
- Freeze‑drying and grinding recommended for organotin cations to achieve homogeneity.
- TTBT (peralkylated) must be determined on field‑moist samples to avoid evaporation losses.
- Other validated pretreatment methods may be used if suitability is demonstrated.
- Extraction / derivatization:
- Two alternative extraction approaches, both followed by in‑situ derivatization with a tetraethylborate reagent and simultaneous extraction into hexane:
- Acidic treatment (acetic acid).
- Alkaline treatment (methanolic KOH) - recommended for matrices with high organic/biological content.
- Organotin cations are determined after derivatization (converted to neutral derivatives); peralkylated TTBT is measured directly.
- Clean‑up and analysis:
- Silica gel and aluminium oxide clean‑up options are provided.
- Gas‑chromatographic separation and detection (including GC‑MS identification guidance) are specified; instrumental conditions and validation data are included in informative annexes.
- Quality control:
- Calibration, internal standards, recovery checks and expression of results are defined.
- Tests must be performed by qualified personnel using appropriate laboratory safety practices.
Practical applications and users
- Environmental testing laboratories conducting routine or investigative analyses for organotin contamination in soils, sediments and wastes.
- Remediation consultants and contaminated‑land specialists assessing historic TBT/organotin pollution from antifouling paints, industrial discharges or landfill leachate.
- Regulatory agencies setting compliance monitoring, risk assessment and site‑characterization programs.
- Research laboratories studying organotin fate, transport and ecotoxicology in soils and sediments.
Related standards
- ISO 22892 - Guidelines for identification of target compounds by GC and MS (referenced for GC‑MS identification).
- ISO 3696 - Water for analytical laboratory use.
- ISO 11465 - Determination of dry matter and water content.
- ISO 16720 - Pretreatment by freeze‑drying for subsequent analysis.
Keywords: ISO 23161, organotin compounds, soil quality, gas chromatography, GC‑MS, TBT, TTBT, derivatization, sample pretreatment, limit of quantification.