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 butachlor immunoassay 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 in a percentage ratio of 85 : 15, respectively. For the second scheme, the detection of butachlor in butachlor in rice-containing products is shown at 80-132% of the added analyte. A comparison of sample preparation methods allows us to recommend: (a) extraction of butachlor with hexane and re-dissolution of the dry residue in a buffer with 15% methanol or (b) preparation of a methanol extract followed by 6-fold dilution with a buffer solution.