A serious problem in analyzing pesticide residues in foods by gas chromatography/mass spectrometry (GC/MS) is the matrix enhancement e ect. e matrix e ect of pesticides in 5 types of representative samples preprocessed by the Positive List System was measured at 100 ppb. e mean matrix e ect value of pesticides in potato, spinach, orange, brown rice, and soybean sample was 129%, 191%, 171%, 225%, and 146%, respectively. Continuing research showed that the sample solutions contained high amounts of some matrix components, such as tocopherols, sterols, and monoacylglycerols. In order to investigate which component causes the matrix e ect, each matrix solution was prepared at 1-1000 ppm (monoacylglycerols: 1-500 ppm), and the pesticide mixture was forti ed to 100 ppb. e matrix e ect depended on the concentration of the matrix solution, and we concluded that monoacylglycerols were the most attributable components to the matrix e ect.
The matrix effect is often observed when trace levels of pesticides in agricultural products are analyzed by GC/MS. In this study, we created a gold-plated ion source that included an ion source body, a draw-out plate lens, and an interface socket. When agricultural products fortified with a pesticide at 100 ppb were tested by GC/MS equipped with a gold-plated ion source, the matrix effect was reduced. The rates of decrease in the matrix effect value in samples of potato, spinach, orange brown rice, and soybean were 2.3%, 14%, 20%, 38%, and 15%, respectively. The rate of decrease was especially significant in the sample of brown rice. This result showed that the gold-plated ion source effectively reduced the interaction between the food matrix and the ion source.
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