Critical evaluation of internal standardization in ICP tandem mass spectrometry and feasibility of the oxygen reaction for boron determination in plants
The feasibility of internal standardization and the oxygen reaction in ICP-MS was studied for accurate determination of boron. Lithium, Be and Rh were systematically evaluated as internal standards (I.S.) for B determination in plants by ICP-MS/MS using a single quadrupole mode and MS/MS mode with O2 into a cell, where B and internal standard signal intensities were processed either after both or only one of them reacted. Carbon is a source of spectral and matrix interferences in B determination by ICP-MS. The use of instrumental strategies such as tandem mass spectrometry (MS/MS) concomitantly with internal standardization demands further investigation about the I.S. behaviour regarding the gas phase reaction with oxygen. The behaviours of B and Be, as well as their oxides, were quite similar in an octopole reaction system containing O2. The coexistence of spectral and non-spectral interferences was evidenced by increasing carbon concentrations in samples and checking positive errors caused for 11B+. Recoveries for B determination in plant certified reference materials without I.S. ranged from 98 to 145% and with Be as an internal standard ranged from 98 to 108%. Beryllium presented favourable characteristics as an internal standard for B due to its mass closeness, similar ionization energy, and reactivity with oxygen.