A new purification method based on a thiol silica column for high precision antimony isotope measurements

Abstract

In this study, a new purification procedure for high precision Sb isotopic analysis was developed by using a thiol silica gel column and is applied to determine Sb isotope composition in natural water samples affected by mining activities. In our proposed procedure, Sb(V) was firstly pre-reduced with 0.5% (w/v) KI–ascorbic acid mixed solution and then Sb(III) in the solution could be separated and purified simply by elution with hydrochloric acid. With the developed procedure, the recovery of antimony was greater than 95.2% and blank values were <0.1 ng. An Apex Ω desolvating sample introduction system was used to improve the sensitivity during Sb isotopic measurement by MC-ICP-MS, and the instrumental mass discrimination was corrected using the sample–standard bracketing (SSB) method combined with the In doping technique. Isobaric effects, matrix effects, and concentration effects were all investigated in detail. ¹²³Sb/¹²¹Sb ratios could be measured with a precision of 0.04‰ (2SD). To verify the reliability of the new method, both matrix containing mixed interference elements and a simulated matrix prepared by Sb standard reference material BHVO-2 doping with Spex Sb standard solution were determined. No measurable Sb isotope fractionation was observed with the developed thiol silica gel column procedure. Finally, natural water samples collected from Lengshuijiang were analysed, and significant Sb isotope variations (−0.20 to 0.27‰) were observed, which suggests that Sb isotopes may provide a promising tool to study antimony migration and pollution.