Selenium measurement in sulphides by hydride generation high-resolution inductively coupled plasma mass spectrometry

Selenium concentrations of transition metal sulphides, albeit low, may he an important tool in exploration for economic ore deposits. These low concentrations necessitate the use of hydride generation for sample introduction, a very sensitive means of pre-concentration that results in low interference. However, transition metals interfere with the production of selenium hydride so that their removal from solutions made from dissolution of transition metal sulphides is necessary for hydride generation of selenium to be effective. We have devised a two step process for the determination of Se concentrations in small samples (c. 50 mg) of sulphide minerals wherein dissolved transition metals are removed by precipitation as metal hydroxides under alkaline conditions (pH c. 12) to prevent sorption of Se, followed by further metal removal by chelating resin. Determinations made by hydride generation inductively coupled plasma mass spectrometry on the CCU-1c certified reference material (copper concentrate) and concentration standards showed quantitative recoveries (100 +/- 5%) of Sc. Using this technique we find that sulphide minerals from the Horne volcanic-hosted massive sulphide deposit give high Sc concentrations ranging from 250 to 750 mu g g(-1). Average precision expressed as relative standard deviation, is 10% and the detection limit is 4 mu g g(-1) of Se in a sulphide mineral. The procedure offers a method for Se determination of sulphides that is operationally simpler than many other methods.