HPLC determination of oxadiazon in commercial pesticide formulations

Abstract

Um procedimento simples, rápido e preciso de cromatografia líquida de alta eficiência (HPLC) foi desenvolvido para a determinação de oxadiazona em formulações concentradas de pesticidas emulsificáveis. 20 µL de amostra, diluída em acetronitrila, foram injetados em uma coluna Kromasil C18 (250 × 4,6 mm, 5 µm), usando acetonitrila:água (80:20) como fase móvel, numa velocidade de fluxo de 1 mL min -1 . Oxadiazona foi determinada por medidas de absorbância a 292 nm. Obteve-se, usando-se o procedimento desenvolvido, um limite teórico de detecção de 0,02 µg mL -1 , um limite de quantificação de 0,047 µg mL -1 , correspondendo a 0,02 e 0,07% m/v na amostra original e desvio padrão relativo de 0,08%, para três análises em replicata de amostras contendo 25% m/v de oxadiazona. A precisão do método foi evidenciada pelas porcentagens de recuperação de 98% a 99% para amostras contendo 0,015 a 0,085 mg de oxadiazona, assim como pela comparação entre os resultados encontrados pelo procedimento recomendado e pela espectrofotometria de infravermelho com transformada de Fourier (FTIR), para amostras reais de produtos formulados.A simple, fast and precise high performance liquid chromatographic (HPLC) procedure has been developed for the determination of oxadiazon in emulsifiable concentrated pesticide formulations. 20 µL of diluted sample in acetonitrile were injected in a Kromasil C18 (250 × 4.6 mm, 5 µm) column, using acetonitrile:water (80:20) as mobile phase at 1 mL min -1 flow rate and oxadiazon determined by absorbance measurement at 292 nm. A theoretical limit of detection of 0.02 µg mL -1 , a limit of quantification of 0.047 µg mL -1 , corresponding to a 0.02 and 0.07% m/v in the original sample, and a relative standard deviation of 0.08% for three replicate analysis of samples containing 25% m/v. Oxadiazon were achieved using the developed procedure. The accuracy of the whole method was evidenced by recovery percentages from 98% to 99% for samples spiked with 0.015 to 0.085 mg oxadiazon as well as by the good comparability between results found by the recommended procedure and by Fourier Transform Infrared (FTIR) spectrophotometry for actual samples of formulated products.Keywords: oxadiazon, high performance liquid chromatography, UV-Vis detection, pesticide formulations IntroductionOxadiazon, 5-tert-butyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2(3H)-one, is a selective pre-emergence herbicide used for the control of annual grasses and many broadleaf weeds in turf and landscape ornamentals. The relatively low toxicity by ingestion and by dermal route of this herbicide is one of the reasons for its widespread use. Methods based on gas chromatography with flame ionization, 3,4 electron capture, 4 mass spectrometry 5 and nitrogen-phosphorous 4 detection, have been proposed for the determination of oxadiazon residues at trace levels after different clean-up and preconcentration steps, being used the aforementioned procedures in various types of matrices such as river and tap waters, foods and mussels.High pres...