Annlytrca Chrmrca Acta, 229 (1990) 227-238 Elsevler Science Publishers B.V., Amsterdam - Pnnted m The Netherlands 227 Effects of concentrated matrices on the determination of trace levels of platinum and gold in aqueous samples using solvent extraction-Zeeman effect graphite furnace atomic absorption spectrometry and inductively coupled plasma-mass spectrometry SCOTT A. WOOD * and DIMITRI VLASSOPOULOS Department of GeoIogrcaZScrences and the Mmeral ExpIoratron Research Insirtute, M&U U‘nrversrty, 3450 Unrversrty St, MontreaL Quebec H3A 2A 7 (Canada) ALFONSO MUCCI Department of Geologrcal Scrences, M&N Unrversrty, 3450 Unrversriy St, Montreal, Quebec H3A 2A7 (Canada) (Received 1st March 1989) SUMMARY .Two methods of determmmg trace levels of platinum and gold m aqueous sofutlons with high contents of total dissolved sohds were mvestlgated The first mvolves preconcentratlon and separation of the precious metals from the mterfenng matnx by solvent extraction, followed by graphte furnace atormc absorption spectrometry (GFAAS) wtth Zeeman effect background correctlon The direct determmatlon of Pt and Au m soluttons of h@ lomc strength by GFAAS 1s not desirable because of interference between elements m the matnx and the analyte, increased lmpreclston of analysis, greatly increased background absorbance Ieadmg to Increased detectton hnuts and rapld detenoratlon of the grapfute tube AfI the extraction methods for gold examined m this study resulted m decreased lmpreclston, increased senslttvlty and Iower background absorbance compared with direct measurements on the aqueous solution. AIL tecfmlques also exfublted good recovenes (> 89%) and reproduclblhtles (relative standard devlatton < 10%) The highest sensttlvtttes for gold extractton from dtstdled water were obtained for dlbutyl sulfide (DBS)-toluene and the Iowest for cyanide-dlbutyl ketone. The degree of extraction of Au was, however, dependent on the composltlon of the solution, indicating that standard and sample matrices should be closely matched even when employmg solvent extraction. Solvent extraction was generally less successful for Pt. In order to obtain an acceptable lmpreclslon m the Pt extractions, It was found that the use of SnCl, as a Iabdzmg agent 1s essenttal for most of the techmques mvesttgated The second method was direct measurement by mductlvely coupled plasma mass spectrometry (ICP-MS) ICP-MS offers the advantages of a very low detection hnut (100 ng 1-l or better) wtthout preconcentratton and a large dynarmc range However, severe matnx effects can occur m concentrated solutions Whereas htgh concentrations m sorutton of both sodmm perchlorate and sodium chlonde decrease the sensltlvlty, the presence of sulfide and natural organic (fulvtc) acid increase the sensitivity for Pt and Au by a factor of up to 4 Sulfate, on the other hand, decreases the sensltlvlty of ICP-MS for Pt The method of standard additions or isotope ddutlon IS recommended for routine use to circumvent this problem, especially when the nature of the matrix IS unknown or cannot be easily matched m the standards. Recently described experiments designed to required the determination of these elements at measure the solubdities of gold and platinum m the 0.1-100 pg 1-l level m the presence of high aqueous fluids of geological interest [1,2] have concentrations of total dissolved solids. Further, 0003-2670/90/$03 50 0 1990 Elsevler Science Publishers B V