Temperature-programmed capillary-HPLC/atmospheric pressure chemical ionization-MS for analysis of fatty acid methyl esters.

A new capillary HPLC method with the atmospheric pressure chemical ionization-MS was developed for the analysis of fatty acid methyl esters and long-chain alcohols. The chromatographic separation was achieved using a Zorbax SB-C18 HPLC column (0.3 x 150 mm, 3.5 mum) with a mobile phase composed of acetonitrile and formic acid and delivered isocratically at a flow rate of 10 muL/min. The column temperature was programmed simply, using a common column oven. Good reproducibility of the temperature profile and retention times were achieved. The temperature programming during the isocratic HPLC run had a similar effect as a solvent gradient; it reduced retention times of later eluting analytes and improved their detection limits. Two atmospheric pressure chemical ionization sources of the MS detector were compared: an enclosed conventional ion source and an in-house made ion source with a glass microchip nebulizer. The enclosed source provided better detectability of saturated fatty acid methyl esters and made it possible to determine the double bond positions using acetonitrile-related adducts, while the open chip-based source provided better analytical figures of merit for unsaturated fatty acid methyl esters. Temperature-programmed capillary HPLC is a promising method for analyzing neutral lipids in lipidomics and other applications. This article is protected by copyright. All rights reserved.