Quantitative analysis of biological and chemical insecticide mixture by capillary electrophoresis

Diazinon has been used widely for eradication of harmful insects. However, due to the induction of insect resistance and considerable toxicity to humans and cattle, its usage has been restricted. In efforts to minimize these untoward side effects, investigators have observed a marked synergistic insecticidal activity when diazinon or its analogues were mixed with β-exotoxin, a bioinsecticide found in Bacillus thuringiensis. This compound is also known as thuringiensin. For developing the lowest effective dose of diazinon to exert the optimal synergistic action, a fast and accurate quantitative analytical method for both compounds is required for this process. Capillary electrophoresis (CE) is a new analytical technique, which provides simple and rapid analysis with high accuracy and high efficient separation. In addition, it can be used to analyze either hydrophilic or hydrophobic compounds by modifying its running buffer. In this study, a quantitative analysis of the mixture of diazinon and β-exotoxin was demonstrated by using CE. In this study micellar electrokinetic capillary chromatographic (MEKC) mode was used because Diazinon has relatively higher hydrophobicity and is easier to be dissolved in MEKC running buffer and is not easily precipitated during the electrophoresis. The running buffer contained 20 mM disodium hydrogen phosphate, 20 mM boric acid, and 100 mM sodium dedocyl sulfate (SDS). The final mixture contained 20% acetonitrile. For quantitative analysis, a fixed amount of tryptophan was used as an internal standard. The standard linear regression equation was generated by using peak area ratio (diazinon to tryptophan) as the y-axis and the concentration of diazinon as the x-axis. From this equation, and similar equations previously established for quantitative analysis of β-exotoxin, the amounts of diazinon and β-exotoxin were calculated. With this method, the ratio of two insecticides can be monitored for making a minimized toxic and maximal effect formulation of combined chemical and biological insecticide.