Influence of organic solvents on the results of immunoenzyme determination of herbicide butachlor: selection of sample preparation modes

The influence of organic solvents such as methanol and acetonitrile on the results of immunodetermination of butachlor in samples of rice and rice products was studied. The schemes of enzyme immunoassay using: (a) native antiserum containing specific antibodies to butachlor and antispecies antibodies labeled with horseradish peroxidase, and (b) biotinylated specific antibodies and streptavidin labeled with peroxidase are considered. The close values of IC₁₀ (0.77 and 0.68 ng/ml, respectively) and working range (2.6–165 and 2.4–192 ng/ml, respectively) were established for the two schemes, when analyzing in a mixture of phosphate buffer and methanol 85 : 15%. For the second scheme, the detection of butachlor in samples of rice and food products based on it is shown at a level of 80–132% of the administered amount of the analyte. The comparison of sample preparation methods allows us to recommend the extraction of butachlor with hexane with redissolution of the dry residue in a buffer with 15% methanol, or the preparation of a methanol extract followed by a 6-fold dilution with a buffer solution.