Direct screening and confirmation of benzene, toluene, ethylbenzene and xylenes in water.

A novel, straightforward sample screening method for benzene, toluene, ethylbenzene and xylene isomers (BTEX) in water is proposed. The method is based on the direct coupling of a headspace (HS) sampler with a mass spectrometer by using a chromatographic column heated to 200 degrees C as an interface. Samples are acidified and subjected to the headspace generation process, the resulting volatile fraction being directly introduced into the source of the mass spectrometer. The large number of samples to be analyzed and the wide range of m/z ratios scanned (75-110) suggest the use of chemometric approaches based on pattern recognition techniques (PRT). For sample classification purposes, the detection limit of the method (overall response 4.0 ng/ml BTEX) was selected as the cut-off level. The method proved highly reliable as no false negatives were obtained at the legally established concentration levels. Positive water samples were confirmed by using the same instrumental setup as in the screening method, but by heating the chromatographic column at 40-200 degrees C to separate the analytes.