Abstract
Improvement of the commercially available fenitrothion-ELISA kit for soil residue analysis was examined. Recovery trials were conducted with 5 soils spiked at 0.5 μg/g soil. Interference of soil matrix was not adequately removed by the addition of synthetic zeolite in extraction, although it reduced Ca2+ concentration. Ultrafiltration at 9 kDa after dilution of the soil extracts gave enough results to compare with those obtained by gas chromatography. It was suggested that overestimation in ELISA was caused by high-molecular-weight humus-like compounds in soil extracts.
