Developments of micro liquid chromatography—mass spectrometry with gradient elution : Improvements to obtain less thermal decomposition of labile compounds

Abstract

Fused-silica columns (I.D. 0.22 mm) packed with ordinary small particle liquid chromatographic material were used in direct connection to an electron impact ion source. The electrostatic field between the column end and an extraction—focusing plate, located close to the ion source inlet, was used for nebulization of the solvent. The ion source was modified to obtain higher efficiency and to reduce the thermal decomposition of labile compouds. A system for micro flow gradients (less than 2 μl/min) has been developed. The flow of a pumping medium (glycerol) is divided into two parallel streams and the flow distribution is controlled using the temperature depedence of the viscosity. The glycerol flow is changed by two “media converters” to the chromatographic solvents. Applications of micro liquid chromatography—mass spectrometry are shown for a plant allelochemical, dhurrin, obtained from Sorghum leaf extract. Mass spectra of glucose, neral, geranial, chlorsulphuron, myoinositol, 3,5,-dinitrobenzoic acid, amtriptyline, 10-hydroxyamitriptyline and omeprazole after liquid chromatography are shown.