Development of an on-line solvent extraction system for electrothermal atomic absorption spectrometry utilizing a new gravitational phase separator. Determination of cadmium in natural waters and urine samples

A novel flow injection (FI) on-line solvent extraction preconcentration/separation system coupled to electrothermal atomic absorption spectrometry (ETAAS), which can tolerate high aqueous to organic flow rate ratios, was developed. The organic extract was effectively separated from a large volume of aqueous phase in a newly designed gravitational phase separator. The performance of the system was illustrated for ultra-trace cadmium determination using ammonium diethyldithiophosphate (DDPA) as chelating agent and isobutyl methyl ketone (IBMK) as extractant. The ETAAS determination and solvent extraction are successfully synchronized through a parallel-operated sequence. The obtained enrichment factor was 24.6 with a sampling frequency of 30 h(-1). The detection limit was 2.8 ng l(-1) and the precision (RSD at 0.2 mg l(-1) Cd) was 3.2%. The proposed method was evaluated by analyzing certified reference materials and applied to the analysis of natural waters and urine samples.