Comparison of normal and low-flow torches for inductively coupled plasma mass spectrometry using optimized operating conditions

Abstract

Simplex optimization has been used in order to optimize inductively coupled plasma (ICP) operating conditions for ICP mass spectrometry (namely nebulizer, auxiliary and coolant gas flows and forward power), using a standard and a low-flow torch. The signal intensity for In⁺ at m/z 115 was used as the criterion of merit. Analyte signals were lower by a factor of approximately 3 for the low-flow torch compared with the standard torch. The Ba²⁺:Ba⁺ ratio was greater by a factor of 7 for the low-flow compared with the standard torch, while the BaO⁺:Ba⁺ ratios were low for both torches. The ArO⁺:In⁺ and ArN⁺:In⁺ ratios were higher for the low-flow torch, and the ArAr⁺:In⁺ ratios were low for both torches. A relatively flat mass response curve was obtained using the low-flow torch, indicating that mass discrimination effects were less pronounced for ions extracted from the plasma formed using this torch. Plasma stability was better with the low-flow torch compared with the standard torch when introducing volatile organic solvents.