Analysis of the squalestatins by on‐line packed capillary liquid chromatography combined with electrospray mass spectrometry

Abstract A mixture of four squalestatins was separated anil characterized by gradient packed capillary liquid chromatography combined with electrospray collision‐induced dissociation mass spectrometry (ESI/CID/MS). Negative‐ion ESI was found to afford spectra typified by strong pseudo‐molecular ions but providing little structural information. Structural information was obtained using an ion‐focusing RF‐only octapole lens to provide conditions for CID. The new method showed improvements in sensitivity when compared to existing thermospray and dynamic liquid secondary‐ion mass spectrometry methods.