Synchronous second-derivative fluorimetric determination of carbaryl and 1-naphthol using solid-phase extraction

Carbaryl and its main metabolite, 1-naphthol, were determined simultaneously using a synchronous second-derivative fluorimetric method. The presence of cetyltrimethylammonium bromide resulted in a four-fold increase in the fluorescence intensity of 1-naphthol together with a large bathochromic shift of the emission spectrum, ca. 100 nm. The synchronous second-derivative spectra of carbaryl and 1-naphthol in the mixture in the presence of CTAB were completely separated by changing the synchronous wavelength interval: with 63 nm the second-derivative spectra of carbaryl were recorded, while with 163 nm those of 1-naphthol appeared. The intensities in the spectra were proportional to the concentration of carbaryl and 1-naphthol. The calibration graphs were linear up to at least 1 x 10(-6) M, and both the correlation factors and detection limits were 0.997, 2.61 x 10(-8) M for carbaryl and 0.999, 2.87 x 10(-8) M for 1-naphthol. Carbaryl and 1-naphthol were completely recovered with a Sep Pak Plus C18 cartridge from some environmental water samples with an adjusted pH of below 6.5, and were successfully determined by the proposed method.