Determination of trace amounts of carbaryl in water by solid-phase laser-induced fluorescence

A quick and very sensitive method is proposed for the determination of the insecticide carbaryl, following transformation in 1-naphthol, using solid-phase fluorescence excited by a pulsed nitrogen laser and detected with a charge-coupled device. Carbaryl is hydrolized in an alkaline medium resulting in 1-naphthol. This hydrolysis product is fixed on QAE Sephadex A-25 gel at pH 11.20. The fluorescence of the gel, packed in a 1 mm silica cell, was measured directly using a solid-surface attachment. The detection limit obtained was 1.8 ng. A recovery study was carried out on several types of water samples to check the efficiency of the method. The results obtained are compared with data published in a previous paper where the LS-50 spectrofluorimeter was used. The detection and quantification limits are improved here by an order of magnitude.