Um método espectrofotométrico novo e altamente sensível foi desenvolvido para a determinação do inseticida cipermetrina em níveis de partes por milhão. O método é baseado na hidrólise alcalina de cipermetrina ao íon cianeto, o qual reage posteriormente com iodeto de potássio e leuco cristal violeta. A absorção máxima do corante cristal violeta formado é medida em 595 nm em meio ácido. A lei de Beer é obedecida no intervalo de concentração de 3,0 a 17 μg, em um volume final da solução de 25 mL (0,12-0,68 ppm). A absortividade molar e sensibilidade de Sandell encontradas foram 3,3×10 5 L mol -1 cm -1 e 0,054 μg cm -2 , respectivamente. O desvio padrão e desvio padrão relativo foram ± 0,001 e 0,22%, respectivamente. O método é simples, sensível e livre de interferências de outros pesticidas e íons. Outros inseticidas piretróides não interferem no método proposto. O método tem sido aplicado satisfatoriamente para a determinação de cipermetrina em amostras ambientais e biológicas.A new and highly sensitive spectrophotometric method was developed for the determination of parts per million levels of widely used cypermethrin insecticide. The method is based on alkaline hydrolysis of cypermethrin to cyanide ion, which further reacts with potassium iodide and leuco crystal violet. The absorption maxima of the crystal violet dye formed was measured at 595 nm in acidic medium. Beer's law obeys over the concentration range of 3.0 to 17 μg in a final solution volume of 25 mL (0.12-0.68 ppm). The molar absorptivity and Sandell's sensitivity were found to be 3.3×10 5 L mol -1 cm -1 and 0.054 μg cm -2 , respectively. The standard deviation and relative standard deviation were found to be ± 0.001 and 0.22%, respectively. The method is simple, sensitive and free from interferences of other pesticides and diverse ions. Other pyrethroid insecticides do not interfere in the proposed method. The method has been satisfactorily applied to the determination of cypermethrin in environmental and biological samples.

A new and highly sensitive spectophotometric method is developed for the determination of parts per million levels of widely used organophosphorus pesticide monocrotophos. The method is based on alkaline hydrolysis of monocrotophos to N-methylacetoacetamide followed by coupling with diazotized p-amino acetophenone in alkaline medium. The absorption maxima of the reddish-violet coloured compound formed is measured at 560 nm. Beer's law is obeyed over the concentration range of 1.2 to 6.8 mg in a final solution volume of 25 mL. The molar absorptivity and Sandell's sensitivity were found to be 7.11 0 5 (±100) L mole -1 cm -1 and 0.008 mg cm -2 , respectively. The standard deviation and relative standard deviation were found to be ± 0.005 and 2.05%, respectively. The method is simple, sensitive and free from interferences of other pesticides and diverse ions. The method has been satisfactorily applied to the determination of monocrotophos in environmental, agricultural and biological samples.