Combined use of collision cell technique and methanol addition for the analysis of arsenic in a high-chloride-containing sample by ICP-MS

Abstract

Feasibility of collision cell (CC) technique with the aid of a methanol modifier for the trace determination of arsenic (As) in a high-chloride-containing sample using ICP-MS was assessed to eliminate the analytical bias induced by polyatomic interference from (ArCl+)-Ar-40-Cl-35 without decreasing As-75(+) intensity, thereby lowering the limit of detection (LOD). The signal intensity of 2% HCl measured at 75 m/z was suppressed entirely by introducing He gas into the CC at a flow rate of at least 3 mL min(-1). Results from the calibration experiments revealed that excess He gas in the CC could also decrease the As-75(+) intensity. Therefore, an optimized He flow rate should be employed, which seemed to be 3 mL min(-1) in this study. To obtain greater sensitivity in the As analysis, the effect of methanol added to the sample solution in varying concentrations (0 to 5% v/v) was assessed. In accordance with previous studies, 3% methanol addition improved As sensitivity by a factor of 2.5 to 3. Also, the methanol addition seemed to decrease the formation of (ArCl+)-Ar-40-Cl-35. Overall, the combined use of both strategies with optimized conditions achieved a lower LOD value of 3 ng L-1 with a high accuracy. (C) 2015 Elsevier BM All rights reserved.