Interpretation of electrospray/ion trap mass spectra of bile acids and other surfactants.

Electrospray spectra of various bile acids and other surfactants were obtained using an ion trap instrument. Bile acids and bile acid derivatives such as 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) self associate to form micelles in a stepwise process. Their spectra show a distinct pattern of aggregation, with ions evenly separated in the m/z space. A new parameter, n/z, can be used to characterize such ions, where n is the number of molecules and z is the charge of the aggregate. The values of z were determined using multi-stage mass spectrometry (MS(n)) and high resolution in the ion trap. Copyright 2000 John Wiley & Sons, Ltd.