Collision-induced dissociation of ions within the orifice-skimmer region of an electrospray mass spectrometer

An equation was derived to describe the variation of the gas number density within the region between the orifice and the skimmer of an electrospray i onization mass spectrometer. The equation was used to develop a semiquantit ative model to predict the value of orifice voltages that lead to ion fragm entation within this region. This model made it possible to predict the typ es of solvent adducts observed for analytes at various orifice voltages. In addition, it is shown that a small number of high-energy collisions is equ ally effective for collision-induced dissociation as compared to a large nu mber of low-energy collisions. Finally, this model is tested with different background electrolyte solutions and a different electrospray mass spectro meter. It is demonstrated that controlled fragmentation studies can be perf ormed on single-quadrupole mass spectrometers, and the proposed model gives a reasonable description of the fragmentation process in both spectrometer s.