Effect of sample dilution on matrix effects in pesticide analysis of several matrices by liquid chromatography-high-resolution mass spectrometry.

This study used two LC columns of different adsorbents and liquid chromatography-electrospray ionization-high-resolution mass spectrometry to study the relationship between matrix effects (ME), the LC separations, and elution patterns of pesticides and those of matrix components. Using calibration standards of 381 pesticides at three dilution levels of 1×, 1/10×, and 1/100×, 108 samples were prepared in solvent and five different sample matrices for the study. Results obtained from principal component analysis and slope ratios of calibration curves provided measurements of the ME and showed the 1/100× sample dilution could minimize suppression ME for most pesticides analyzed. Should a pesticide coeluting with matrix components have a peak intensity of 25 times or higher, the suppression for that pesticide would persist even at 1/100× dilution. The number of pesticides had enhancement ME increased with increasing dilution from 1× to 1/100×, with those early eluting, hydrophilic pesticides affected the most.