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.
Analysis of butter fat triacylglycerols by supercritical fluid chromatography/electron impact mass spectrometry.
Triacylglycerols (TAGs) from butter fat isolated by solvent extraction were analyzed by use of a capillary column supercritical fluid chromatograph (SFC) combined with a flame ionization detector or a double focusing mass spectrometer. The chromatographic separation was achieved by using a dimethyldiphenylpolysiloxane phase (DB-5) to bundle up the TAGs with the same carbon number. The ratio of TAGs with varying degree of unsaturation in each SFC peak was determined by using the selected ion monitoring of the molecular ions with electron impact mode. The discrimination between the fatty acids at the position sn-2 and positions sn-1/3 in a triacylglycerol molecule was demonstrated by monitoring the ions [M - RCO2CH2]+ from reference compounds.
Catalytic removal of tert-butyldimethylsilyl (TBS) ether by PVP-I
Abstract A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.