ISO 23631:2006 specifies a method for the determination of dalapon, trichloroacetic acid (TCA) and selected haloacetic acids in ground water and drinking water by gas chromatography (GC-ECD and/or GC-MS detection) after liquid-liquid-extraction and derivatization using diazomethane. Depending on the matrix, the method is applicable to a concentration range from 0,5 to 10 micrograms per litre. The validated reporting limit of TCA and dalapon is about 0,05 micrograms per litre. Detection by electron-capture detector (ECD) in general leads to lower detection limits. Detection by mass spectrometry (MS) allows analyte identification.