First experimental proof of asymmetric charge transfer in ICP-MS/MS (ICP-QQQ-MS) through isotopically enriched oxygen as cell gas
The quantification of a variety of elements in the field of ICP-MS is restricted by isobaric interferences. The recent development of ICP-MS/MS (“triple quadrupole” configuration) offers a new way to solve the problem of the detection of such elements affected by interferences because the signal caused by either the analyte or the isobaric interference can be shifted to another m/z through reactions with the cell gas (oxygen, ammonia or hydrogen). This system consists of two quadrupoles (Q1 and Q2) with a collision/reaction cell in between. When using the MS/MS mode of this configuration it becomes possible to restrict the ions entering the cell to a defined m/z and therefore get a better insight into the reactions possibly occurring within the collision/reaction cell. While using oxygen as a cell gas analyte ions can undergo oxygen transfer as well as asymmetric charge transfer reactions. As a proof for the latter reaction two types of measurements have been carried out, using both oxygen with natural isotopic composition and isotopically enriched oxygen (97% 18O2) as cell gases.