Development of a kinetic spectrophotometric method for insecticide diflubenzuron determination in water and baby food samples

A kinetic spectrophotometric method for determining residues of insecticide diflubenzuron 1(4-chlorphenyl)-3-(2,6-diflubenzoyl)urea (DFB) has been developed and validated. Kinetic method was based on the inhibitory effect of DFB on the oxidation reaction of sulfa nilic acid (SA) by hydrogen peroxide in the presence of Co2+ ions in a phosphate buffer, which was monitored at 370 nm. DFB can be measured in the concentration interval 0.102 - 3.40 mu g mL(-1) and 3.40 - 23.80 mu g mL(-1). The detection and quantification limits of the method were calculated according to the 3 sigma criteria and found to be 0.077 mu g mL(-1) and 0.254 mu g Ml(-1), respectively. The relative standard deviations for five replicate determinations of 0.102, 1.70 and 3.40 mu g mL(-1) DFB were 2.08, 1.22 and 1.21 %, respectively, for the first concentration interval, and the recovery percentage values were from 94.12 to 97.35 %. HPLC method was used as a parallel method to verify results of the kinetic method. The kinetic method was successfully applied to determine diflubenzuron concentrations in spiked water and baby food samples after solid phase extraction of the samples. The F and t values at 95% confidence level are lower than the theoretical ones, confirming agreement of the developed and the HPLC method.