Integrating preconcentration, tetrahydroborate immobilization, elution and chemical vapor generation onto a cellulose surface for the determination of cadmium with atomic fluorescence spectrometry

A cellulose fibre packed micro-column was used for sorption preconcentration of ultra-trace cadmium and successive coating of a thin layer of sodium tetrahydroborate solution. The retained cadmium was stripped with hydrochloric acid and in- situ vapor generation on the cellulose surface was initiated by reaction with the coated layer of reducing reagent. The vapor was detected by atomic fluorescence spectrometry (AFS). The integration of preconcentration, reducing reagent immobilization, elution and in- situ vapor generation onto the cellulose surface significantly simplifies the entire operation, where a single syringe pump suffices fluids delivery, providing sufficient stability and long-term reliability indicated by an intra-day RSD <5%. In addition, the detection limit and precision were significantly improved with respect to those obtained by a conventional elution approach. With a sampling volume of 1.0 mL, a quantitative retention of cadmium was obtained within a linear range of 0.01-1.0 mg L-1, along with an enrichment factor of 19.5 and a sampling frequency of 12 h(-1). A precision of 1.9% at 0.2 mg L-1 was obtained and a detection limit of 3 ng L-1 was derived. The procedure was validated by analyzing certified reference materials of Riverine Water (SLRS-4), and Trace Elements in Water (GBW 08608), in addition to spiking recovery in a coastal sea water.