Development of multi residue analysis of herbicides in cereal grain by ultra performance liquid chromatography electrospray ionization mass spectrometry.
A rapid and sensitive method was developed for the determination of 50 herbicides in cereal grain by ultra performance liquid chromatography electrospray ionization mass spectrometry (UPLC ESI MS) Using acetonitrile effectively extracted 22 kinds of triazine and other basic herbicides, and using 90:10 v/v acetonitrile phosphate buffer (pH 7.5) effectively extracted other 28 herbicides. Chromatographic separation was achieved using gradient elution with acetonitrile water as a mobile phase for 22 triazine and phenylurea herbicides and with 5mM ammonium acetate aqueous solution containing 0.1% formic acid acetonitrile as a mobile phase for other 28 herbicides. Using matrix matched standard calibration curve effectively reduced the indirect matrix effects, ensured accurate quantification for these herbicides. The response was linear over two orders of magnitude with a correlation coefficients (r(2) higher than 0.992. The limits of quantification for the herbicides varied from 0.2 to 25.6 mg kg( 1) The intra and inter day precisions (relative standard deviation, RSD) were 2.2 9.3% and 5.7 17.1% respectively. The recovery varied from 61.6% to 110% with the RSD of 1.6 11.8% Analyzing soybean, corn and wheat samples from 17 counties evaluated this method. The developed and validated method has high sensitivity, satisfactory recovery and precision, can ensure the multi class multi residue analysis at low mg kg( 1) level for the most herbicides in cereal grain.
Food chemistry