Spectrophotometric determination of lead with N-hydroxy-N,N '-diphenylbenzamidine and diphenylcarbazone in airborne dust particulates and soil

A simple, selective and sensitive method for the spectrophotometric determi nation of lead in airborne dust particulate and soil samples is described. The method is based on the selective extraction of lead at pH 10.0 +/- 0.2 with N-hydroxy-N,N'-diphenylbenzamidine (HDPBA). The yellow Pb-II-HDPBA com plex shows maximum absorbance at 410 nm with a molar absorptivity of 1.6 x 10(4) l mol(-1) cm(-1). The sensitivity of the method is further increased by the addition of a methanolic solution of diphenylcarbazone (DPCZO) to th e extract. The pink Pb-II-HDPBA/DPCZO complex has a molar absorptivity of 7 .2 x 10(4) l mol(-1) cm(-1) at lambda(max) = 525 nm. The detection limit of the method is 4 ng ml(-1) in the organic phase and the Sandell's sensitivi ty of the method is 0.0015 mu g cm(-2). The relative standard deviation for 10 replicate measurements of Pb at a level of 1.0 mu g ml(-1) is 1.5%. The method has been successfully applied to the determination of Pb-II in airb orne dust particulates and soil samples.