Submitted to: Analytical and Bioanalytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2011
Publication Date: 10/2/2011
Publication URL: http://handle.nal.usda.gov/10113/62034
Citation: Byrdwell, W.C. 2011. 'Dilute-and-shoot' triple parallel mass spectrometry method for analysis of vitamin D and triacylglycerols in dietary supplements. Analytical and Bioanalytical Chemistry. 401:3317-3334. Interpretive Summary: A method for analysis of vitamin D and triacylglycerols (edible fats and oils) in dietary supplement gelcaps that eliminates all chemical pre-treatment has been developed. The contents of whole gelcaps are transferred to a vial, an internal standard is added, and the solution is diluted to constant volume---a relatively simple process. Vitamin D3 is measured using ultraviolet detection at 265 nm, as well as several types of mass spectrometry, in which different masses and their fragments are used to identify and quantify the vitamin. Two different types of mass spectrometry are also used for analysis of the triacylglycerols (TAGs) in the rice bran oil that the vitamin D is dissolved in. The analysis of TAGs is very sensitive, and allows new TAGs to be identified that have not been reported before. Also, multiple units of the TAGs are identified; some consist of two units, some three units, and some four units of TAGs connected to each other. Glycerin, a compound present as a filler in many gelcaps, is also detected as being present bonded into multiple units in the gelcap, reported for the first time. Before the availability this new method, all of the information about TAGs present in the gelcap would normally have been lost by conventional chemical treatment prior to analysis. Also, this new 'dilute-and-shoot' method provides much more information in less time than conventional analyses. The gelcaps analyzed contained more than the label amount of vitamin D3. The method will be of considerable value to those engaged in research in which vitamin D or lipid analysis is required.
Technical Abstract: A method is demonstrated for analysis of vitamin D-fortified dietary supplements that eliminates virtually all chemical pretreatment prior to analysis, and is referred to as a ‘dilute and shoot’ method. Three mass spectrometers, in parallel, plus a UV detector, an evaporative light scattering detector (ELSD), and a corona-charged aerosol detector (CAD), were used to allow a comparison of six detectors simultaneously. Ultraviolet data was analyzed using internal standard, external standard, and response factor approaches. The contents of gelcaps that contained 2000 IU (50 mcg) vitamin D3 in rice bran oil (RBO) were analyzed without the need for lengthy saponification and extraction. Five gelcaps were analyzed, each in triplicate, using vitamin D2 as an internal standard, by comparison to a three-point calibration curve. Vitamin D3 was analyzed using UV detection, extracted ion chromatograms, selected ion monitoring (SIM) atmospheric pressure chemical ionization mass spectrometry (APCI-MS), and two transitions of multiple reaction monitoring (MRM) APCI-MS. The triacylglycerols (TAGs) in the oils were analyzed using full-scan APCI-MS, electrospray ionization (ESI) MS up to MS4, an ELSD, and a CAD. The method proved to be very sensitive for vitamin D3 as well as TAGs, allowing identification of intact TAGs containing fatty acids up to 28 carbons in length. LC-ESI-MS of glycerin polymers is also demonstrated. All gelcaps analyzed contained more than the label amount of vitamin D3.