Development of solid extraction unit for determining multiple herbicides in maize

A multiclass method for the determination of five selected sulfonylurea, diphenylether, and sul fonanilide herbicides commonly used in maize growing has been developed. In this study, the method development for the analysis was performed using a solids extraction unit for analyte extraction from maize. A procedure using solid phase extraction system for clean up the methanolic extract, and a liquid chromatography-tandem mass spectrometry (MS/MS) was developed for the final determination. The extraction parameters that were studied included temperature, duration of the static extraction, sample amount, solvent volume, and flow rate. Maximum yield was obtained by extraction with 25 mL of pure methanol at 50 degreesC and a flow rate of 1 mL min(-1). After extraction, herbicides present in methanolic phase were isolated and cleaned up by solid phase extraction using a reversed-phase C-18 cartridge and Carbograph-1 cartridge. The herbicides were chromatographically separated using reversed-phase HPLC and selectively analyzed by MS/ MS using a positive ionization-turbo ion spray (PI-TISP) interlace in multiple reaction monitoring (MRM) mode.