A new system for lipid analysis by liquid chromatography-mass spectrometry

Abstract

A simple system for interfacing liquid chromatography with mass spectrometry for the analysis of lipids is described. The system is based on the moving chain transport principle and employs an endless stainless steel belt of perforated construction that gives it superior surface properties and capacity to entrain solvent. The entire column eluent is collected on the belt which transports it into an evaporator where the solvent is removed. The solute, which remains as a residue on the belt, is transported into a reactor where it is converted to hydrocarbons by reaction with hydrogen at 400–450 C. The hydrocarbons, which are characteristic of the structures of the parent compounds, are swept into an outlet tube where ca. 15% are drawn into the ion source of a mass spectrometer operating in the chemical ionization mode using methane as the reagent gas. The spectrum is recorded on an oscillographic recorder for identification purposes. Detection and quantitative analysis is performed by single ion monitoring of the most intense ion using a conventional analog recorder. The system is demonstrated by application to a standard mixture of tripalmitin, cholesteryl palmitate, and cholesterol separated on a 3.2×250 mm silica column, and exhibited a sensitivity of ca. 1 nanogram per component injected on the column.