ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY IN CHOLESTEROL OXIDE DETERMINATION AND CHARACTERIZATION

An atmospheric pressure chemical ionization liquid chromatography/mass spectrometry (APCI-LC/MS) system was evaluated for the analysis of ch olesterol oxidation products (COPs). High performance liquid chromatog raphy separation of these compounds was performed under reversed-phase chromatographic conditions at 1 mL/min how rate. Useful mass spectra for confirmation and quantitation purposes were obtained with positive -ion detection. The influence of several parameters, such as the tempe rature of the heated nebulizer interface, the voltage applied to the o rifice and to the ring electrode on the mass spectra of the analytes, was studied and optimized in order to obtain the best sensitivity. Lin earity, sensitivity and precision of the method were determined operat ing in the selected-ion monitoring mode. Detection limits were in the range 0.2-0.8 ng for all the compounds with linear calibration graphs in the 0.1-10 mg/L concentration range. The method was applied to the quantitative analysis of COPs in lyophilized beef preparations, and re sults were compared with those obtained using LC/UV and LC/MS with par ticle beam interface. (C) 1998 John Wiley & Sons, Ltd.