ANALYSIS OF HIGH-PURITY REAGENTS USING AUTOMATIC ONLINE COLUMN PRECONCENTRATION-SEPARATION AND ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A fully automatic flow-injection on-line column preconcentration and separation procedure for electrothermal atomic absorption spectrometry is described for the determination of cadmium and lead in high-purity reagents. A microcolumn with 9 muL of solid sorbent, introduction of air prior to elution, and use of methanol as the eluent made it possible to elute the sorbed analyte quantitatively with only 80 muL of solvent. The total eluate volume was transferred into the graphite tube which was pre-heated to 80-degrees-C using a flow rate of 0.08 mL min-1 which allowed the solvent to evaporate in part during eluate introduction. The efficiency of the total procedure was 0.63 and 0.65, and the enrichment factor was 62 and 64 for cadmium and lead, respectively, compared with the direct introduction of 30 muL of an aqueous solution. The sample throughput was 13 h-1 for a sample loading time of 60 s and the detection limits (3 sigma) were 0.7 and 4.5 ng L-1 for cadmium and lead, respectively. The relative standard deviation of the entire procedure in the optimum working range was typically around 3% (n = 6). A number of high purity (suprapure) and analytical grade (pro analysi) reagents were analyzed, and spiking experiments resulted in recoveries of 97-104%.