Analysis of information sources in references of the Wikipedia article "Electrospray ionization" in English language version.
An evaluation of the electric field on the drop surface at the point when it just ceases to be spherical (yet carries the total ion charge z) indicates that small PEG ions may be formed by ion evaporation. The break observed in the charge distribution may perhaps mean that the shift from the Dole to the ion evaporation mechanism arises at m(unintelligible)104[clarification needed], though this inference is highly hypothetical.
For most published data examined, zmax is between 65% and 110% of zR, providing strong support in favor of Dole's charged residue mechanism, at least for masses from 3.3 kD up to 1.4 MD. Other large but less compact ions from proteins and linear chains of polyethylene glycols (PEGs) have zmax values considerably larger than zR, apparently implying that they also formas charged residues, though from non-spherical drops held together by the polymer backbone.
The data do show a nearly discontinuous jump in the observed m/z for a mass somewhere between 20,000 and 50,000, and it is tempting to conclude that this is due to a corresponding transition where the ionization mechanism shifts from one type to the other. This would correspond to a critical value of z in the vicinity of 50, with a corresponding electric field of 2.6 V/nm. Of course, this is entirely hypothetical, and there is yet no compelling evidence of any kind indicating that an ion with as many as 30 charges can be formed by field evaporation.
