HPLC-MS/MS Determination of Residual Amounts of Chlormequat and Mepiquat in Grains with Solid Phase Extraction

Sample of grains was extracted with methanol-H2O(1+1) solution ultrasonically. The extract was purified by passing through the Strata-X-C SPE column and eluting with mixture of methanol and 0.2 mol·L-1 ammonium acetate solution (1+1). The eluate was evaporated rotationally to near dryness, and made up its volume to 1 mL with acetonitrile-H2O(2+3) solution. Aglient ZORBAX RX-SIL (3.0 mm×100 mm, 1.8 μm) chromatographic column was used for separation, using a mixture of acetronitrile and 10 mmol·L-1 ammonium acetate solution (containing 0.1% of formic acid ) mixed in ratio of 20 to 80 as mobile phase for elution (flow rate: 0.3mL·min-1). ESI with positive ionization mode and multiple reactions monitoring mode were used in the MS/MS analysis. Linear relationships between values of peak area and mass concentration of chlormequat and mepiquat were found in the same range of 0.2-10 μg·L-1, with detection limits (3S/N) of 0.02 and 0.05 μg·kg-1 respectively. Test for recovery was made by standard addition method, giving values of recovery and RSD′s (n=5) in the ranges of 80.1%-104.7% and 2.5%-9.3% respectively.