Ten years of liquid chromatography-mass spectrometry

Thermospray-LC-MS analysis of various groups of polyphenols in tea. I. Catechins, flavonol O-glycosides and flavone C-glycosides

This paper describes the application of thermospray-HPLC-MS (buffer ionization mode, single-stage MS, positive ion detection) to the analysis of flavanols (catechins), flavonol O-glycosides, flavone C-glycosides as well as caffeine, theobromine, theogallin and theanine from tea. All compounds are detected as pseudo-molecular ions [M+H]+. Other molecular ion species are adducts with sodium, potassium, ammonium and solvent clusters. The catechin gallates and the flavonol glycosides are fragmented. The fragmentation is temperature dependent. The glycoside bond is labile and consequently the flavonol glycosides have the protonated aglycone as this base peak. The ester bonds in the catechin gallates are more stable and the fragmentation is limited. The fragment pattern contributes to the structural information. LC-thermospray-MS is a good analytical tool for identifying the polyphenols mentioned above both in tea and other foodstuffs, especially in method development and structural elucidation.

Determination of polycyclic aromatic hydrocarbons by high-performance liquid chromatography-particle beam-mass spectrometry

In this article, we report a high-performance liquid chromatography-particle beam-mass spectrometric (HPLC-PB-MS) method for the determination of polycyclic aromatic hydrocarbons (PAHs). The PB interface consists of a concentric ultrasonic nebulizer with temperature-controlled desolvation chamber and a three-stage momentum separator. The HPLCPB-MS method showed greater sensitivity for PAHs with molecular weights above 178 than for those PAHs with molecular weights below 178. The percent relative standard deviations for the determination of 0.5 ng chrysene, 1.0 ng dibenzo[a,h]anthracene, 1.0 ng benzo[g,h,i]perylene, and 2.5 ng coronene were 20%, 2.5%, 13.7%, and 6%, respectively. The detection limits at signal/noise = 3 were 0.2 ng for chrysene, 1.0 ng for dibenzo[a,h]anthracene, 0.5 ng for benzo[g,h,i]perylene, and 1.5 ng for coronene.

Use of particle beam liquid chromatography-electron impact mass spectrometry for structure elucidation of oxodipine and three of its metabolites

In order to test the analytical capabilities of the particle beam liquid chromatograph-mass spectrometer interface in structural identification in drug metabolism, a liquid chromatographic-mass spectrometric (LC MS) method using this new technique was developed for oxodipine and some of its expected metabolites. After two extraction steps at pH 9 and 1.5, the separation of the compounds, which have a wide polarity range, was carried out by an isocratic high-performance liquid chromatographic method with a 25-cm cyano-bonded column. The compounds were eluted with hexane-methanol-methylene chloride (76:12:12). Mass spectra were recorded after electron impact ionization (75 eV) with a source temperature of 150 degrees C. Under these conditions, comparison of the spectra with those obtained after gas chromatography or with a direct introduction probe showed identical fragmentation patterns when a sufficient amount of product was injected for LC-MS analysis.