Column solid phase extraction and determination of ultra-trace Au, Pd and Pt in environmental and geological samples

A new sorbent based on cysteine modified silica gel (SiG-cys) was prepared and studied for preconcentration and separation of noble metals Au(III), Pd(II), Pt(II), Pt(IV). Its extraction efficiency was examined by batch and column solid phase extraction procedures. Laboratory experiments performed showed that sorbent is characterized with high selectivity, permiting quantitative sorption (93-97%) of noble metals Au, Pd and Pt from acidic media 0.1-2 mol L-1 HCl and unsignificant sorption (less than 2%) for common base metals like Cu, Fe, Mn and Zn. The analytes retained on the sorbent are effectively eluted with 0.1 mol L-1 thiourea in 0.1 mol L-1 HCl and measured by ETAAS or ICP OES under optimal instrumental parameters. The sorbent showed high mechanical and chemical stability and extraction efficiency was not changed after 500 cycles of sorption/desorption. The sorbent was successfully applied in analyticals procedures for preconcentration and determination of Au, Pd and Pt in geological and soil samples. Detection limits (3 sigma criteria) achieved, depending on the instrumental methods used are: ETAAS (0.005 mu g L-1 for Au in river and sea water, 0.002 mu g g(-1) for Au in copper ore and copper concentrate); ICP OES (0.03 mu g L-1 for Pd and 0.06 mu g L-1 for Pt in river and sea water, 0.006 mu g g(-1) for Pd in copper ore and copper concentrate and 0.002 mu g g(-1) for soluble Pt in soil). The accuracy of the procedures developed was confirmed by added/found method for sea and river water; by the analysis of national certified materials (copper ore and copper concentrate for Au and Pd) and by determination of the sum of soluble Pt(II) Pt(IV) in spiked soil samples. (C) 2011 Elsevier B.V. All rights reserved.