Abstract
A simple and rapid indirect spectrophotometric method for determination of methamidophos in water, soil and vegetable samples has been described. Methamidophos reacts with acid produced from p-dimethylaminobenzaldehyde (p-DMAB) as a result of Cannizaro’s reaction. The resultant adduct undergoes condensation reaction in acidic medium forming a yellow colored product. Absorbance of the colored product was measured at 405 nm and pH 3 against a reagent blank. The Beer’s law range is obeyed in the range 1-30 µg mL-1 with molar absorptivity of 2.8 ×103 L mol-1 cm-1. The limit of detection and quantification were found to be 0.20±0.03 and 0.60±0.04 µg mL-1 respectively. The proposed method was effectively applied for determination of methamidophos in various samples with percent recoveries in the range of 96±0.08 to 102±0.06 %. KEY WORDS: Spectrophotometric, Methamidophos, p-Dimethylaminobenzaldehyde (p-DMAB), Cannizaro’s reaction Bull. Chem. Soc. Ethiop. 2015, 29(2), 311-318DOI: http://dx.doi.org/10.4314/bcse.v29i2.13
Highlights
Methamidophos (O,S-dimethylphosphor-amidothiolate) is a broad spectrum, water soluble, systemic organophosphorus insecticide and acaricide [1]
A number of analytical methods have been reported for determination of methamidophos
The proposed reaction mechanism described in Scheme 1 shows that p-dimethylaminobenzaldehyde molecule undergoes Cannizaro’s reaction in basic medium
Summary
Methamidophos (O,S-dimethylphosphor-amidothiolate) is a broad spectrum, water soluble, systemic organophosphorus insecticide and acaricide [1]. A number of analytical methods have been reported for determination of methamidophos These include gas chromatography-mass spectrometry [5], high performance liquid chromatography [6], adsorptive stripping square wave voltammetry [7], differential pulse stripping voltammetry [8] and acetylcholine enzyme sensor [9]. Some of these methods like GC and HPLC being highly sensitive and specific, need complicated pre-treatment and clean-up steps [10] and are, unsuited for rapid assay of samples. Sodium hydroxide (2.5 mol L-1) and hydrochloric acid (3.0 mol L-1) solutions were prepared by dissolving appropriate amounts in distilled water and diluted to 100 mL with distilled water
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