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Comparison of gas and high performance liquid chromatography with selective detection for determination of triazine herbicides and their degradation products extracted ultrasonically from soil

GC and HPLC with selective detectors were compared for simultaneous determination of triazine herbicides simazine, atrazine, propazine, terbuthylazine, cyanazine, ametryn, prometryn, and atraton, and of their dealkylated degradation products in soil. The compounds were ultrasonically extracted from spiked agricultural soil samples (organic matter content <5 %) with a 2:1 acetone:n-hexane mixture. High efficiency of GC capillary column and high selectivity of the thermionic sensitive detector (TSD) and ion trap detector (ITD), made it possible to directly analyse uncleaned soil extracts and determine all 12 compounds in one run. In reversed-phase HPLC with diode-array detector (DAD), the co-elution of soil matrix components interfered with the determination of methylthiotriazines and terbuthylazine. The recovery of triazine compounds, determined by GC-TSD, from a silty sand soil (organic matter content 1.82 %, pH 6.22) spiked at levels 15-600 ng/g, were 70-90 % (RSD 9-19 %), except for deisopropylatraton (38 %). GC-TSD analysis with detection limits of 5-15 ng/g for chloro- and methylthiotriazines and 30 ng/g for methoxytriazines was more sensitive than GC-MS(ITD). GC analysis with electron capture detection was sensitive for some chlorotriazines, but a reliable compound quantification in complex chromatograms of uncleaned soil of extracts was not possible. For all compounds save didealkylatrazine, HPLC-DAD was at least two times less sensitive than GC-TSD. Soil/sediment organic matter, clay and silt content, and pH were identified as matrix characteristics which might affect ultrasonic extraction recovery of a particular compound.

Triazine herbicides; soil ultrasonic extraction; chromatographic analysis; selective detection

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