Matrix behavior during sample preparation using metabolomics analysis approach for pesticide residue analysis by GC-MS in agricultural products.

The detailed matrices and their behaviors during pesticide residue analyses were clarified using a metabolomics analysis approach. The matrix profile was investigated using two different extraction solvents, acetone and acetonitrile. Acetone extracted the matrix components with a wide range of log P(O/W) values. Components with log P(O/W) values >10, such as sterols and tocopherols, and components with log P(O/W) values <3.2 were more extracted by acetone than by acetonitrile. In contrast, components with log P(O/W) values in the range from 3.2 to 10 were extracted by both acetone and acetonitrile at the same concentration level. The study also examined the difference in the column cleanup efficiency using a solid phase extraction (SPE). Florisil, silica gel, NH(2), PSA, and GCB were selected as representative columns for pesticide residue analysis, and acetone extraction of brown rice was selected in this experiment. Most of the matrix components were removed by either column, whereas monoacylglycerols, which are the components causing the matrix effect, were not removed by any column. Understanding such a detailed matrix behavior helps to develop a better analytical method for pesticide analysis using GC-MS.

Development of an enzyme-linked immunosorbent assay (ELISA) for residue analysis of the fungicide azoxystrobin in agricultural products.

A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) was developed for residue analysis of azoxystrobin in garden crops, for which the maximum residue limits (MRLs) are 0.5-50 mg/kg in Japan. For hapten synthesis, an ethyl carboxyl group was introduced to the 4-position of the 2-cyanophenoxy group in azoxystrobin, and its cyano group was changed to a methyl group. An anti-azoxystrobin monoclonal antibody was prepared from mice immunized with hapten-keyhole limpet hemocyanin conjugate. The dc-ELISA using prepared antibody showed 50-250-fold higher sensitivity compared to the MRLs. The working range of the dc-ELISA was 10-200 ng/mL. The dc-ELISA showed high specificity to azoxystrobin. When methanol extracts from nine kinds of garden crops spiked with azoxystrobin ranging near the MRLs were analyzed, the determined results by the dc-ELISA agreed well with the results of their controls. In addition, azoxystrobin spiked in garden crops homogenates was satisfactorily extracted by methanol solution and easily analyzed. The recovery rate of dc-ELISA was 96-109% and correlated well with the results obtained by HPLC analysis.