Quantitation of natural triacylglycerols by reversed-phase liquid chromatography with direct liquid inlet mass spectrometry.
Using acetonitrile and propionitrile as eluting solvents and reagent gases the yields of both quasi-molecular and fragment ions were found to vary with the molecular weight, degree of unsaturation and positional distribution of the fatty acids in the triacylglycerol molecule, and appropriate calibration factors were necessary for accurate quantitation. In the absence of pure structural isomers and mixed acid standards, preliminary calibration factors have been determined for total ion and specific ion current responses by comparing the peak area ratios obtained by liquid chromatography-mass spectrometry with the proportions of the molecular species known to be present in randomized oils and in natural oils of known chemical composition. Although the derived factors include both chromatographic and mass spectrometric effects and are obtained with a gradient of reagent gases, they appear to be generally applicable. It was shown that positional isomers affected the yield of the (MH-RCOOH)+ ions over a 1-3-fold range of intensities, while the nature of the fatty acid affected it over a range of 1.25-fold. After suitable calibration of the relative ion responses it was possible to determine the identities and amounts of the individual molecular species in natural fats and oils.
Quantitative analysis of triglycerides using atmospheric pressure chemical ionization-mass spectrometry
Atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) was used for quantitative analysis of triglycerides (TG) separated by reverse-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 and normal soybean oils and of randomized and normal lard samples. Quantitation of the TG by four approaches based on APCI-MS were compared, and these were compared to quantitation obtained using liquid chromatography (LC) with flameionization detection (FID). The APCI-MS methods were based on (i) calibration curves from data for mono-acid TG standards, (ii) response factors obtained from a synthetic mixture of TG, (iii) response factors calculated from comparison of randomized samples to their statistically expected compositions, and (iv) response factors calculated from comparison of fatty acid (FA) compositions calculated from TG compositions to FA compositions obtained by calibrated gas chromatography (GC) with FID. Response factors derived from a synthetic mixture were not widely applicable to samples of disparate composition. 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/APCI-MS which were undetected using LC-FID. Two quantitation methods, based on response factors calculated from randomized samples or on response factors calculated from FA compositions, both gave similar results for all samples. The TG compositions obtained using response factors calculated from FA compositions showed less average relative error than was obtained from LC-FID data, and were in good agreement with predicted compositions for the synthetic mixture and for randomized soybean oil and lard samples.
Simulation Analysis of Local Heat Treatment Formability of an Aerospace Aluminum Alloy Frame Parts
Wang Zhijian1,a, Guo Fangyu1,b, Shang Xiaofeng1,c, Song Hongwu2,d, Wang Ling3,e and Wang Jiale1,f 1School of Mechatronics Engineering, Shenyang Aerospace University, Shenyang 110136, China 2Institute of Metal Research, Chinese Academy of Science, Shenyang 110016, China 3Shenyang aircraft industry company, Shenyang 110134, China aWangzhijian1974@sina.com, b1486121506@qq.com, c1009074102@qq.com dhwsong@imr.ac.cn, ew_ling2008@aliyun.com, f1591897439@qq.com