Up-front CID

The effect of inducing fragmentation by collisional activation can also be achieved through collision with solvent molecules in the API ion source. Various implementations of this procedure are called up-front CID, cone voltage fragmentation and poor man s MS-MS. Results obtained this way are comparable to true MS-MS product ion spectra. The strict interpretation of the results in terms of precursor-product ion relationships is lost, but this limitation does not negate the utility of the method when a true tandem instrument is not available. 

Mild up-front CID reduces the abundance of background ions, a distinct advantage for LC/MS or CE/MS where the contribution of background ions to the baseline noise in the total ion current trace is a serious problem. ... 

Removal of the last solvent molecule(s) from a sample ion by up-front CID may not be possible without unintended fragmentation of a labile sample ion. 

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