engleski

Comparison of HPLC-DAD, GC-MS and GC-NPD techniques for analyses of triazine compounds in styrene-divinylbenzene extracts of urine

A solid-phase extraction procedure on styrene-divinylbenzene (SDB) followed by high performance liquid chromatographic (HPLC-UV diode array detection) analysis enables an efficient trace enrichment and sensitive determination of triazine herbicides (atrazine, simazine, prometryn, ametryn) and two monodealkylated atrazine metabolites in human urine [1]. The procedure is based on forcing the 5-ml urine sample through the sorbent using the positive air pressure, rinsing the cartridge with 1% aqueous acetonitrile solution in order to eliminate the polar urinary interferences, and elution of retained triazine compounds with acetone. The eluate is evaporated under a stream of nitrogen to the aqueous residue that is diluted with water for HPLC analysis. The main drawback of this procedure is that it does not allow the determination of didealkylated atrazine despite its efficient retention on the SDB sorbent. This metabolite is completely lost during wash out of the cartridge with aqueous acetonitrile solution. To omit the washing out step and to improve the recovery of urinary didealkylated atrazine the procedure was optimised for gas chromatographic analysis with nitrogen selective (GC-NPD) or mass selective (GC-MS) detection. After urine percolation the cartridge is washed out with pure water. To the aqueous residue obtained after evaporation of the acetonic eluate sodium sulphate is added and the concentrated triazine herbicides and the three atrazine metabolites are efficiently reextracted into ethyl acetate. Due to the mass selective detection (ion trap detector) the GC-MS analysis of ethyl acetate extracts enables a sensitive determination of all analysed compounds. The sensitivity of the GC-MS method ranges from 10 ng/ml for atrazine, simazine and deethylatrazine to 25 ng/ml for didealkylated atrazine. However, the GC-NPD analysis is suitable only for determination of chlorotriazines because of a number of urinary interfering peaks overlapping with the peaks of methythiotriazines. The detection limit of atrazine, simazine and atrazine metabolites of 10 ng/ml is comparable with the sensitivity of the HPLC determination. The reextraction of urinary triazines from the aqueous residue after evaporation of the acetonic eluate into n-hexane gives the interference-free GC-NPD chromatograms but it is not efficient for extraction of mono- and didealkylated atrazines. [1] G. Mendaš, V.Drevenkar, L. Zupančič-Kralj, J. Chromatogr. A 918 (2001) 351-359.

Triazine compounds; urine; solid-phase extraction; HPLC-DAD; GC-NPD; GC-MS

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