Determination of Ultra-Trace Amounts of Lead in River Water by Flow Injection Analysis Coupled with Computer-Controlled Auto-Pretreatment System Using Solid Phase Extraction Procedure

Flow injection analysis (FIA) system coupled with a computer-controlled auto-pretreatment (Auto-Pret) system (MGC Auto-Pret 018S) was newly developed for the determination of ultra-trace amounts of Pb(II) in aqueous samples. The solid phase material, Analig Pb-01 (GL Sciences), was packed in a mini-column (2 mm i.d. x 40 mm length), which was installed in the Auto-Pret system. In the mini-column, ultra-trace amounts of Pb(II) were selectively adsorbed and concentrated on Analig Pb-01, and Pb(II) adsorbed was eluted with an eluent (3 M KCl). After the eluent passed through the column, the sample zone of Pb(II) in the effluent was retained in the loop of a sample injection valve in the FIA system; then it was introduced in a carrier stream (CS), which was merged with a reagent solution (RS) containing 4-(2-Pyridylazo)resorcinol (PAR) as a coloration reagent (pH 10.2). The absorbance of the colored Pb(II) chelate with PAR was measured at 530 nm, and recorded as a peak with a chart recorder. The concentration efficiency of lead by the proposed FIA system coupled with the Auto-Pret system was 3 with a 5-mL sample and 15 with a 20-mL sample. The limit of detection (LOD) corresponding to 3 σ of reagent blanks was 0.5 x 10 M using a 20-mL sample, and the lower limit of quantification (LOQ) was 1.0 x 10 M. The proposed technique was applied to the determination of trace Pb(II) in a river water sample; 4.3 x 10 M Pb(II) was determined; the result of recovery tests were 99% to 101%. The proposed FIA system coupled with the Auto-Pret system will be suitable for measuring the regulated values of waste waters (0.1 mg/L), environmental waters (0.01 mg/L) and WHO Guidelines of lead in drinking water (0.01 mg/L).