Answer 7.5

a) Can you tell the difference between EC and CE?

EC means electron capture which generates negative radical ions, while CE stands for charge exchange (more recently termed charge transfer, CT) that forms positive radical ions.

b) What is the role of the gas in EC?

Different from true CI techniques where the reagent gas forms reactive ionic species, the role of the gas in EC is merely to moderate the electrons to thermal velocity which is prerequisite for the EC process.

c) Enumerate the processes of ion formation upon EC and write down the corresponding equations.


d) Can you imagine useful applications of EC?

EC is useful for all analytes having a high electron affinity (EA). Thus, EC offers extremely low detection limits with most environmental pollutants and hazards such as pesticides, chlorophenols, explosives and their residues, polychlorinated biphenyls, dibenzodioxines and dibenzofuranes, for example.