Determination of lead in tap water by ICP-AES with flow-injection on-line adsorption preconcentration using a knotted reactor and ultrasonic nebulization

A flow injection inductively coupled plasma atomic emission spectrometry method for the determination of lead in tap water is described. The method employs on-line preconcentration in a knotted reactor and ultrasonic nebulization. Lead-diethyldithiocarbamate complex at pH 9.5 was loaded onto the knotted reactor at a flow rate of 10 ml per minute for 60 seconds, and the complex was eluted with 4.0 mol per litre hydrochloric acid. The total enhancement factor with respect to pneumatic nebulization was 140 (14.8 for ultrasonic nebulization and 9.5 for the knotted reactor). The relative standard deviation for 10 replicate determinations of a standard solution of lead (20 ug per litre) was 2.7 per cent. The calibration graph was linear from levels close to the detection limit up to at least 100 ng per ml. The detection limit obtained for the preconcentration of a 10 ml aqueous solution was 0.2 ug per litre. The method was successfully applied to the analysis of lead in tap water samples.