LEAD PRECONCENTRATION ONTO C-18 MINICOLUMN IN CONTINUOUS-FLOW AND ITSDETERMINATION IN BIOLOGICAL AND VEGETABLE SAMPLES BY FLAME ATOMIC-ABSORPTION SPECTROMETRY

A procedure for the preconcentration and determination of lead in vege table and biological samples was developed in the continuous mode coup led to a flame atomic absorption spectrometer. Lead is quantitatively preconcentrated in acetic buffer as its diethyldithiocarbamate chelate onto a C-18 minicolumn, placed in the loop of a proportional injector , eluted by a stream of methyl isobutyl ketone and introduced directly into the nebuliser. A detection limit of 3 mu g l(-1) is obtained usi ng a time-based technique for 2 min preconcentration and an RSD of 3.8 % was readily achieved for three measurements of 25 mu g Pb l(-1). The sample throughput is 24 h(-1). Using preconcentration times of 10 min an enrichment factor of 189 can be obtained. The continuous flow syst em was used for some reference sample analysis and the obtained result s reveal that the methodology can be easily applied for vegetable and biological sample analysis.