Application of high‐performance liquid chromatography/atmospheric pressure ionization mass spectrometry for the analysis of non‐volatile compounds

The combination of a high‐performance liquid chromatograph and a magnetic type mass spectrometer with an atmospheric ionization source has been applied for analyses of thermolabile compounds, i.e. antibiotics, amino acids and glycosphingolipids. Chromatography was performed on a 4 mm i.d. x 150 mm column packed with 5 μm ODS at a flow rate of 1 ml min −1 . The liquid chromatography/atmospheric pressure ionization (LC/API) magnetic‐type mass spectrometer provides not only an abundant pseudo‐molecular ion but also fragment ions which give a structural information resulting from collision‐induced dissociation at the differential pumping region of the liquid chromatograph/mass spectrometer interface. The isomers of kanamycins could be differentiated from each other on the basis of their mass spectra obtained at the relatively higher drift voltage applied. LC/API mass spectra of leucine and isoleucine were very similar, but it was easy to differentiate one from another by checking the existence of the ions at m / z 43 or m / z 57 in their mass spectra. The LC/API mass spectra of glucosylceramides showed [MH] + ions of good abundance and significant fragment ions useful for chemical characterization at a proper drift voltage setting in a controlled and reproducible manner.