QUANTITATIVE-ANALYSIS OF TRIGLYCERIDES USING ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY

Atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) w as used for quantitative analysis of triglycerides (TG) separated by r everse-phase high-performance liquid chromatography. APCI-MS was used for analysis of mono-acid TG standards containing deuterated internal standard, of a synthetic mixture of heterogeneous TG, of randomized an d normal soybean oils and of randomized and normal lard samples. Quant itation of the TG by four approaches based on APCI-MS were compared, a nd these were compared to quantitation obtained using liquid chromatog raphy (LC) with flame-ionization detection (FID). The APCI-MS methods were based on (i) calibration curves from data for mono-acid TG standa rds, (ii) response factors obtained from a synthetic mixture of TG, (i ii) response factors calculated from comparison of randomized samples to their statistically expected compositions, and (iv) response factor s calculated from comparison of fatty acid (FA) compositions calculate d from TG compositions to FA compositions obtained by calibrated gas c hromatography (GC) with FID. Response factors derived from a synthetic mixture were not widely applicable to samples of disparate compositio n. The TG compositions obtained using APCI-MS data without application of response factors had average relative errors very similar to those obtained using LC-FID. Numerous TG species were identified using LC/A PCI-MS which were undetected using LC-FID. Two quantitation methods, b ased on response factors calculated from randomized samples or on resp onse factors calculated from FA compositions, both gave similar result s for all samples. The TG compositions obtained using response factors calculated from FA compositions showed less average relative error th an was obtained from LC-FID data, and were in good agreement with pred icted compositions for the synthetic mixture and for randomized soybea n oil and lard samples.