The application of collision/reaction cell inductively coupled plasma mass spectrometry to multi-element analysis in variable sample matrices, using He as a non-reactive cell gas

The development of collision and reaction cells for inductively coupled plasma mass spectrometry (ICP-MS) has extended the capability of the technique by allowing the selective attenuation or removal of previously problematic spectral interferences. However, many of the reported applications of collision and reaction cell ICP-MS have required the adoption of operating conditions that are so specific to the selected analyte and/or target interference that the multi-element capability of the instrument has been compromised, or the conditions have been applicable only to a well-defined and consistent sample type. This work demonstrates the application of an ICP-MS, fitted with a collision/reaction cell, to perform multi-element analysis at the single ng ml(-1) level in multiple sample types. A single set of operating conditions was used for all selected analytes across a diverse range of sample matrices. The capability of an octopole-based collision/reaction cell ICP-MS, operated using He as the inert collision gas, was demonstrated for the removal of unidentified polyatomic species arising from variable Cl-, S- and C-based synthetic matrices and round-robin samples comprising a range of clinical matrices. Compared to the standard (no cell gas) mode, the He cell gas mode improved the accuracy of spike recoveries at the 5 ng ml(-1) level for all the measured isotopes of all the transition metals investigated (Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) in the synthetic matrix samples, using the same cell gas and voltage conditions for all analytes in all matrices. Where reference values were available for the clinical samples, analyte recoveries were typically within the range of the expected concentrations, when calibrated using simple (not matched for sample matrix) calibration standards and using operating conditions that were constant for all analytes and all matrices. Additional benefits of using an inert cell gas such as He were the complete absence of newly formed interfering product ion species and freedom from analyte signal reduction through loss by reaction. This is in contrast to the reported generation of new, cell-formed polyatomic ions and the loss of some analytes by reaction, which can occur when highly reactive cell gases are used, and suggests that the use of an inert collision gas may be suitable for the analysis of complex and variable sample matrices, where the identity of any potential interfering species is not known in advance.