Solvolysis kinetic study and direct spectrofluorimetric analysis of the fungicide benomyl in natural waters
MACEDONIAN JOURNAL OF CHEMISTRY AND CHEMICAL ENGINEERING(2014)
摘要
A direct spectrofluorimetric method for the quantitative analysis of benomyl in natural waters is described here. Benomyl is an unstable, fluorescent fungicide that mainly decomposes into carbendazim and n-butyl-isocyanate in organic and aqueous solutions. The kinetics of benomyl solvolysis reactions were investigated in organic solvents (methanol and acetonitrile) and in aqueous solvent systems, including beta-cyclodextrin (beta-CD), sodium dodecyl sulphate (SDS), dodecyltrimethylammonium chloride (DTAC), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium hydroxide (CTAOH), Brij-700, Triton X-100 and water, at different pH and/or NaOH concentrations. The benomyl fluorescence signal was found to be quasi-completely stable in 10(-2) M NaOH aqueous solution, various alkaline (10(-2) M NaOH) organised media, beta-CD neutral solution and Triton X-100 aqueous solutions of different pH. Based on these results, a direct spectrofluorimetric analytical method was developed for the determination of benomyl in 10(-2) M NaOH aqueous solution and Triton X-100 solutions (pH7 and 10(-2) M NaOH), with wide linear dynamic range (LDR) values of two to three orders of magnitude, very low limit of detection (LOD) and limit of quantification (LOQ) values of 0.002-0.5 ng/ml and 0.007-2.0 ng/ml, respectively, and small relative standard deviation (RSD) values of 0.2-1.7%, according to the medium. This direct spectrofluorimetric method was applied to the evaluation of benomyl residues in natural waters, with satisfactory recovery values recorded (87-94%).
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关键词
benomyl,solvolysis kinetics,solvent effects,direct fluorescence analytical method,water analysis
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