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.
Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat
In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C10−C18 fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacyl-glycerol moieties of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C4−C18 fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding in polarity to the chloropropanediol diesters.
Numerical Simulation of Thermal Sensitivity for Explosives
In order to compare the thermal sensitivity of several typical explosives, this article solved numerically one-dimensional transient heat conduction equation including thermal decomposition for explosives with finite difference method. The explicit difference equations under different boundary conditions were established, and the corresponding stability criterion was derived. The ignition times for typical explosives were calculated, which was used to evaluate thermal sensitivity of explosives.