Overview
ISO 23631:2006 defines a validated analytical method for the determination of dalapon, trichloroacetic acid (TCA) and selected haloacetic acids (HAAs) in groundwater and drinking water. The method uses liquid–liquid extraction (commonly with MTBE), concentration, derivatization with diazomethane to form methyl esters, and analysis by capillary gas chromatography with electron-capture detection (GC‑ECD) and/or gas chromatography–mass spectrometry (GC‑MS). Depending on the sample matrix the method is applicable in the range 0.5–10 µg/L, with a validated reporting limit for TCA and dalapon of about 0.05 µg/L. The standard stresses laboratory safety, particularly the hazards of diazomethane, and requires appropriately trained personnel.
Key Topics
- Analytes covered: Dalapon, trichloroacetic acid (TCA) and selected mono-, di-, tri-haloacetic acids (see Table 1 of the standard).
- Sample preparation: Acidification, liquid–liquid extraction (MTBE), salt addition, filtration if suspended solids interfere, and concentration by evaporation.
- Derivatization: Methylation using diazomethane to produce volatile methyl esters suitable for GC analysis - includes preparation and titration checks for diazomethane.
- Detection options:
- GC‑ECD for superior sensitivity (lower detection limits).
- GC‑MS for compound identification and confirmation.
- Performance characteristics: Applicable concentration range (0.5–10 µg/L); validated reporting limit ~0.05 µg/L for TCA and dalapon. Precision and chromatographic examples are provided in informative annexes.
- Quality control: Use of methylated and non-methylated reference standards, internal standards, multipoint calibration, blank controls, and recovery checks for the combined extraction/derivatization procedure.
- Safety and interference notes: Detailed warnings about diazomethane toxicity/explosivity and potential chromatographic interferences from solvents, stabilizers, or reagents.
Applications
- Routine monitoring of drinking water and groundwater for haloacetic acids and dalapon to support regulatory compliance, public health protection and risk assessments.
- Environmental laboratories implementing validated methods for low‑level organic acid residues.
- Water utilities and consultants performing contaminant screening, treatment performance verification, or source-water assessments.
- Research labs needing a standardized GC-based protocol with options for high-sensitivity detection (ECD) or confirmatory identification (MS).
Who should use it: accredited analytical laboratories, water-quality regulators, utilities, environmental consulting firms and researchers requiring a standardized, reproducible method for HAAs and dalapon in potable and groundwater matrices.
Related standards
- ISO 3696 - Water for analytical laboratory use
- ISO 5667-1, -2, -3 - Water sampling guidance (design, techniques, preservation)
Keywords: ISO 23631:2006, water quality, dalapon, trichloroacetic acid, haloacetic acids, GC‑ECD, GC‑MS, liquid‑liquid extraction, derivatization, diazomethane, drinking water monitoring.