engleski

Determination of triazine herbicides and their metabolites in soil

A high-resolution multimethod is presented for simultaneous determination of triazine herbicides simazine, atrazine, propazine, terbuthylazine, cyanazine, ametryn, prometryn, atraton, and dealkylated atrazine and atraton metabolites in agricultural soils. The method involves sonicated extraction of compounds from soil with a 2:1 acetone:n-hexane mixture, and their quantification by reversed-phase high-performance liquid chromatography coupled to diode-array detector (HPLC-DAD) or/and by capillary gas chromatography with nitrogen-phosphorus (GC-NPD) and mass selective (GC-MS) detection. For HPLC-DAD analysis the soil extract was evaporated and the dry residue was redissolved in 0.5 ml of water. The analysis was performed on a 25 cm x 0.4 cm RP-ODS column using gradient elution with phosphate buffer (pH=5) and acetonitrile as the mobile phase. Propazine and ametryn were eluted together, so ametryn was chosen for further HPLC-DAD work. Quantitation of terbuthylazine and prometryn encountered problems due to the co-elution of interfering compounds in the soil extract. GC analysis of concentrated acetone/n-hexane soil extracts on 60 m x 0.25 mm SPB-5 or Rtx-5 columns provided good separation and interference-free determination of all triazines. The HPLC and GC methods showed good linearity and produced consistent results for triazine compounds extraction efficiency over the compound mass fractions in soil ranging from 15 (GC) or 21 (HPLC) to several hundred ng/g. For chlorotriazines the recoveries ranged from 73 to 95% (RSD 7-19%), for methylthiotriazines from 54 to 84% (RSD 12-26%), and of methoxytriazines from 38 to 71% (8-19%). Detection limits of triazine compounds in soil achieved by HPLC-DAD analysis ranged from 10 ng/g for chlorotriazines to 60 ng/g for methoxytriazines. Compared to HPLC-DAD the GC-NPD method demonstrated higher or at least comparable detection sensitivity: 5-15 ng/g for chlorotriazines, 10-15 ng/g for methylthiotriazines and 30-60 ng/g for methoxytriazines. GC-MS (ion trap detector) detection limits ranged between 10 and 20 ng g-1 except for deisopropylatraton (60 ng/g) and didealkylated atrazine (100 ng/g).

Triazine herbicides; soil; ultrasonic extraction; gas chromatography; high performance liquid chromatography

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