Multiresidue analysis of phenylurea herbicides in crops by HPLC with Diode Array detector

A method is proposed for the simultaneousanalysis of 13 pesticides (phenylurea class)in several different crops (vegetables, cereals, fruits, etc). An aliquotof chopped sample is blended with methanol. The resulting aqueous methanol extract is filtered and cleaned up by meansof a double solid phase system. For the first system a C18 reversed phase cartridge was used, while a non-specific material such as graphitized carbon black (Carbopack B) was used for the second system. This is followed by separation and quantificationof thephenylureas using reversed phase gradient elution high performance liquid chromatography with UV detection at 242 nm. The performanceof this method was evaluated by fortifying nine crops with pesticides at 0.05-0.20 ppm. No matrixinterference was observed and the recoveryof the residues variedin the range 76-100%. Using a diode array detector a good security is reached for the identificationof substances.In general, the method appears to be fast and able to detect routinely at the 0.01 ppm level.