Investigations of mixed-gas plasmas using a sheathing device for ICP-MS.

摘要

The effects of the addition of a sheathing gas (Ar, N2, H 2) to form a mixed-gas plasma for ICP-MS were investigated by examining 14 analyte ion profiles (27Al+, 51V +, 52Cr+, 55Mn +, 56Fe+, 58Ni +, 59Co+, 63Cu +, 64Zn+, 75As +, 98Mo+, 114Cd +, 121Sb+, 208Pb +) and the profiles of 3 background species (m/z = 44, m/z = 54, m/z = 78). Profiles of the standard Ar plasma were compared with blank and blank-subtracted sample profiles acquired with the sheathing device present. Similar to other mixed-gas studies, the sensitivity of all analyte ions was reduced in these mixed-gas plasmas. Improvements in the detection limits of some analyte ions were obtained, many being specific to the sheathing gas used. The most significant improvement in detection limit was obtained using a N2 sheath, improving the 56Fe+ detection limit by a factor of 3. Mass discrimination effects were also slightly reduced by each of the sheathing gases. The profiles of N2 sheathed plasmas provided evidence that the sheathing gas does not mix with the nebulizer gas flow. The profiles of the H2 sheathed plasmas showed an elongation of the normal analytical zone.