INFLUENCE OF COEXISTING ANALYTES IN ATMOSPHERIC-PRESSURE IONIZATION MASS-SPECTROMETRY

The sensitivity of atmospheric pressure ionization mass spectrometry to an analyte, in the presence of another analyte with higher proton affinity, was studied by using an EXTREL API-MS/MS system. A simple rate equation analysis was used to model the ion-molecule chemistry occurring in the ionization source. The experimental results obtained for the detection of dimethyl methyl phosphonate, in the presence of varying concentrations of diisopropyl methyl phosphonate, agree with the rate equation analysis. The analysis also indicates that a higher density plasma is better suited for the detection of trace quantities of analytes, in the presence of higher concentrations of other analytes.