Electrospray mass spectroscopy of macromolecule degradation in the electrospray

As previously shown, by electrospraying dilute polystyrene (PS) solutions gas phase macroions can be produced. Degradation of the PS in the electrospray was tested by collecting the electrosprayed PS and measuring its number‐average molecular weight osmotically. About 10% degradation was observed when using negative voltages, but the degradation was considerably reduced when the electrospray occurred in the presence of SF 6 gas. No degradation was apparent in the case of positive sprays. A quantitative analysis of the results was made difficult by a small less of PS in the nitrogen gas stream and by diffusion of lighter ions to the vertical wall of the spray chamber. The latter effect did not occur at the highest spray voltage used, −24 kV.