Trace lead measurement and online removal of matrix interference in geosamples by ion-exchange coupled with flow injection and hydride generation atomic fluorescence spectrometry.

A flow injection method has been developed for the direct determination of free available Pb(II). The method is based on the chemical sorption of Pb(II), from pH7 solutions, on a column packed of chelating resin. The retained complex was afterwards eluted with hydrochloric acid followed by hydride generation with reduction by tetrahydroborate. The preconcentration system proposed in this paper allows the elimination of great part of the saline content in the sample. A thorough scrutiny was made for chemical variables and FI parameters. With a sampling volume of 10.5 mL, quantitative retention of Pb (II) was obtained, along with an enrichment factor of 40 and a sampling frequency of 15 h(-1). The detection limit, defined as 3 times the blank standard deviation (3sigma), was 0.0031 ngml(-1). The precision was characterized by an RSD value of 3.78% (at the 4 ng.ml(-1) level, n = 11). The developed method has been applied to the determination of trace Pb in three standard reference materials. Accuracy was assessed through comparing the results with the accepted values.