On-line dissolution of borate melt for simultaneous matrix isolation, concentration and flame atomic absorption determination of lead in phosphate rock

A previously developed on-line flow injection system for solid sample dissolution is described for matrix isolation, concentration and determination of lead in phosphate rock borate melt with flame atomic absorption spectroscopy (FAAS) detection. The flow system can handle slurries and allow solid sample digestion, simultaneous matrix isolation and analyte concentration. Various flow parameters were optimized including, sample size, flow rate, pH and buffer composition. Compared with direct determination by FAAS, the proposed method resulted in almost total elimination of matrix effect and a 15-fold increase in detectability. Ten samples per hour can be processed and analyzed for lead with a detection limit of 0.13 mug g(-1) using simple equipment and a flame atomic absorption spectrometer. The analytical results obtained by the proposed method compared favorably with those obtained by mixed-acid digestion of the phosphate rock and graphite furnace atomic absorption spectroscopy (GFAAS). (C) 2001 Elsevier Science B.V. All rights reserved.