Determination of low-level pesticide residues in soft drinks and sports drinks by liquid chromatography with tandem mass spectrometry: Collaborative study

Abstract

A collaborative study was conducted on a method for the measurement of 11 low-level pesticide residues in soft drinks and sports drinks by liquid chromatography with tandem mass spectrometry. The pesticide residues determined in this study were alachlor, atrazine, butachlor, isoproturon, malaoxon, monocrotophos, methyl paraoxon, phorate, phorate sulfone, phorate sulfoxide, and 2,4-dichlorophenoxyacetic acid (2,4-D). Blind fortification solutions containing 3 different levels of pesticide residues were provided to 9 collaborating laboratories to create test samples at concentrations of 0, 0.1, and 0.5 μg/L with a 10-fold concentration for phorate In a total of 6 matrixes (2 colas, 1 diet cola, 1 clear lemon-lime soft drink, 1 orange soft drink, and 1 sports drink). Good qualitative performance of the method was demonstrated for all pesticide residues. Reproducibility relative standard deviation (RSDR) ranged from 7 to 151% for alachlor, atrazine, butachlor, isoproturon, malaoxon, monocrotophos, methyl paraoxon, phorate, phorate sulfone, phorate sulfoxide, and 2,4-D at the 0.1 μg/L level (1.0 μg/L for phorate). At 0.5 μg/L (5.0 μg/L for phorate), RSDR ranged from 9 to 57% for alachlor, atrazine, butachlor isoproturon, malaoxon, monocrotophos, methyl paraoxon, phorate, phorate sulfone, phorate sulfoxide, and 2,4-D in all matrixes. Repeatability relative standard deviation (RSD r), applicable to the diet cola and sports drink, ranged from 0 to 124% for the 11 pesticide residues at the 0.1 μg/L level (1.0 μg/L for phorate). At 0.5 μg/L (5.0 μg/L for phorate), RSDr ranged from 4 to 26%. Recoveries for the 11 pesticide residues in all matrixes ranged from 84 to 300% at the 0.1 μg/L level (1.0 μg/L for phorate) and from 66 to 127% at the 0.5 μg/L (5.0 μg/L for phorate) level. Coefficients of determination (r2) of the matrix-matched calibration curves were ≥0.95. It is recommended that the method be accepted by AOAC as Official First Action with a limit of quantification of 0.5 μg/L for alachlor, atrazine, butachlor, isoproturon, malaoxon, methyl paraoxon, monocrotophos, phorate sulfone, phorate sulfoxide, and 2,4-D and 5.0 μg/L for phorate.