INTER-LABORATORY VALIDATION OF SOLID-PHASE MICROEXTRACTION FOR THE DETERMINATION OF TRIAZINE HERBICIDES AND THEIR DEGRADATION PRODUCTS AT NG 1 LEVEL IN WATER SAMPLES/

The accuracy and precision of solid-phase microextraction (SPME) were validated in an inter-laboratory study including ten laboratories for the analysis of triazine herbicides and their metabolites at ng/l leve l in aqueous samples. The SPME conditions were optimised in order to o btain maximum sensitivity. Especially, salt addition and choice of the SPME fibre coated with Carbowax-divinylbenzene increased the sensitiv ity. The average detection limits were in the range from 4 to 24 ng/l for the triazine herbicides, and 20 and 40 ng/l for desisopropylatrazi ne and desethylatrazine, respectively. The average r(2) values of the calibration curves were above 0.99 for all of the analytes. The statis tical data treatment was performed in accordance with the Internationa l Standardisation Organisation (ISO) standard 5725. Relative repeatabi lity standard deviations between 6 and 14% and relative reproducibilit y standard deviations between 10 and 17% were found. The determined co ncentrations of the reference sample compared well to the ''true'' val ues, thus proving the good accuracy of the method. It is concluded tha t SPME is a reliable technique for the quantitative analysis of water samples containing triazine herbicides in concentrations around the Eu ropean limit of 100 ng/l for individual pesticides in drinking water. (C) 1998 Elsevier Science B.V.