Development of a Soil Sample-preparation Method for the Immunoassay of Heptachlors Residues before Cultivation

Heptachlor categorized as one of the persistent organic pollutants (POPs) and its metabolite (heptachlor-cis-epoxide) extremely persist in cultivate fields. To prevent the accumulation of heptachlors in squash, the development of analysis methods that are simple, fast and sensitive, and have high-throughput and the possibility of on-site monitoring for the detection of these contaminants in soil before cultivation is required. Because immunoassay is a rapid, simple and powerful method for high-throughput analysis, it is also widely used in environmental analysis. In this study, sample-preparation method of soil for heptachlors immunoassay was investigated. Soil extracts (extraction buffer, 50 % (v/v) methanol-H2O) were purified by a matrix solid-phase dispersion (MSPD) method using graphite carbon/E-HyCu (R). A column containing graphite carbon/E-HyCu (R) and soil extracts was washed with 50 % (v/v) methanol-H2O, then, heptachlors were eluted with acetonitrile. Any interfering substance on ic-ELISA in soil extracts was effectively removed. The results of heptachlors analysis in soil showed a good correlation (R-2 = 0.966) between immunoassay data obtained by the developed MSPD method and GC-MS data. This suggested that the developed MSPD method is useful for heptachlors immunoassay and may contribute to reducing the risk of the accumulation of heptachlors in squash.