Simultaneous determination of benomyl and morestan residues in waters by synchronous solid-phase spectrofluorimetry.

In this paper a new, sensitive, and simple method for simultaneous determination of pesticides morestan and benomyl at trace levels in waters is reported. Both chemicals, showing native fluorescence in solution at neutral medium, were fixed on C-18 silica gel at pH 1, giving a fluorescent system. The benomyl-morestan-silica gel system, after dry, was packed in a 1-mm silica cell and its synchronous fluorescence spectra were recorded at δλ=80 nm for determination of benomyl and δλ=25 nm for determination of morestan. Measurements of fluorescence were performed at λ1=289 nm and λ2=367 nm for benomyl and morestan analysis, respectively. The applicable concentration ranges were from 0.5 to 15.0 ng·ml(-1) for benomyl and from 0.6 to 15.0 ng·ml(-1) for morestan, with relative standard deviations of 1.2 and 1.5% for benomyl and morestan, respectively, being 0.15 and 0.18 ng·ml(-1) its respective detection limits. The method was applied to the simultaneous determination of residues of both pesticides in water of different provenances.