Spectrophotometric determination of decamethrin and its residues in insecticidal formulations and in water.

Three spectrophotometric methods were developed for the microdetermination of decamethrin in insecticidal formulations and in water. The methods are based on the hydrolysis of decamethrin with methanolic KOH to 3-phenoxybenzaldehyde; condensation of the hydrolysis product with 2,4-dinitrophenylhydrazine (2,4-DNPH), 4-nitrophenyl-hydrazine (4-NPH), or 2,4,6-trinitrophenylhydrazine (2,4,6-TNPH) under alkaline conditions; and measurement of the condensates at the absorption maxima of 444, 535, and 480 nm, respectively. The relationship between absorbance and concentration was linear in the ranges of 0.1-5.0 micrograms/mL, 0.5-7.0 micrograms/mL and 0.1-5.5 micrograms/mL for 2,4-DNPH, 4-NPH, and 2,4,6-TNPH, respectively. The methods are sufficiently sensitive and can be used to detect decamethrin at concentrations as low as 0.1 microgram/mL.