Rapid determination of carbaryl and 1-naphthol at ppt levels in environmental water samples by automated on-line SPE-LC-DAD-FD

A fully automated method, based on on-line solid phase extraction (SPE) then liquid chromatography with diode-array and fluorescence detection, has been developed for the trace-level determination of carbaryl and 1-naphthol, its primary transformation product, in environmental water samples. By means of rapid enrichment on a 30 mm x 4 mm i.d. 10-mu m ODS pre-column, using a 10-mL water sample, before LC determination both compounds were recovered satisfactorily from different environmental water samples spiked at various concentrations (0.05-10 mu g L-1). Average recoveries were between 93 and 102% with coefficients of variation between 1 and 4%; detection limits as low as 10 and 50 ng L-1 (ppt) were estimated for carbaryl and 1-naphthol, respectively. With this small sample volume, sample throughput was up to 30 samples per day. A carbaryl degradation study was performed by spiking a surface-water sample at 2 mu g L-1. After 15 days 80% of the carbaryl was degraded and the presence of 1-naphthol was confirmed by means of its UV spectrum.