ONLINE SORBENT EXTRACTION, PRECONCENTRATION AND DETERMINATION OF LEADBY ATOMIC-ABSORPTION SPECTROMETRY

A method for the quantitative preconcentration of lead based on an exi sting batch process was developed for implementation in a flow system including a flame AAS detector. Lead can be quantitatively preconcentr ated as pyrrolidinedithiocarbamate or dithizonate on an activated carb on minicolumn. The chelates are eluted in methyl isobutyl ketone and i ntroduced directly into the nebuliser-burner. An enrichment factor of 50 is typically obtained for a preconcentration time of 2 min (lead ca n be determined at concentrations between 15 and 400 ng/ml), which res ults in a throughput of ca. 25 samples per hr. The sensitivity achieve d with the two reagents is similar, but the selectivity provided by AP DC exceeds that of dithizone. Based on the results obtained in the det ermination of lead in reference materials (minerals and skim milk), th e proposed APDC method is applicable to real samples.