engleski

Simultaneous determination of chloro-, methylthio- and methoxytriazines in soil

A high resolution gas chromatographic method with nitrogen selective (GC-TSD), electron capture (GC-ECD) or ion selective (GC-ITD) detection was evaluated for simultaneous determination of eight chlorotriazine (atrazine, simazine, terbuthylazine, propazine, cyanazine, deethylatrazine, deisopropylatrazine, deethyldeisopropylatrazine), two methylthiotriazine (ametryn, prometryn), and two methoxytriazine (atraton and deisopropylatraton) herbicides or herbicide metabolites in soil extracts. The compounds were ultrasonically extracted from 5 g of spiked agricultural soil samples with a 2:1 acetone:n-hexane mixture. The extracts were analysed on a 60 m x 0.25 mm i.d. SPB-5 capillary column which enabled good separation of all analytes. The recoveries from spiked soil samples were determined by nitrogen selective detector providing interference-free detection of triazines in soil extracts. At compound mass fractions of about 100 ng/g the recoveries ranged from 85% for simazine to 103% for atrazine. The reproducibility of the determination of chlorotriazine compounds in spiked soil samples, as shown by relative standard deviation, was better than 20%, and that of methylthio- and methoxytriazines ranged from 8 to 26%. The TSD detection limits of triazine compounds in soil ranged from 5 ng/g for chlorotriazines (save didealkylated atrazine with a detection limit of 15 ng/g) to 60 ng/g for deisopropylatraton. The ECD chromatograms of soil extracts were far more complex than TSD chromatograms indicating that an additional clean-up step should be included in the preconcentration procedure. A sufficiently high peak resolution enabled a reliable ECD determination of atrazine, didealkylated atrazine and cyanazine. The ECD sensitivity for two latter compounds in the soil extracts was about 10 times higher than the sensitivity of TSD. However, quantitation of other chloro- and methylthiotriazines encountered problems due to the co-elution of interfering compounds present in the soil extract. ECD did not detect methoxytriazine compounds. Comparison of GC-TSD with GC-ITD determination of triazine compounds in soil extracts indicated superior sensitivity of the TSD.

Chlorotriazine; methoxytriazine; methylthiotriazine; soil; extraction; gas chromatographic method

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