The chemical composition of fingermarks could potentially be important for determining investigative leads, placing individuals at the time of a crime, and has applications as biomarkers of disease. Fingermark samples containing triacylglycerols (TAGs) and other components were analyzed using laser desorption/ionization (LDI) time-of-flight mass spectrometry (TOF MS). Only LDI appeared to be useful for this application while conventional matrix-assisted LDI-TOF MS was not. Tandem MS was used to identify/confirm selected TAGs. A limited gender comparison, based on a simple t-distribution and peaks intensities, indicated that two TAGs showed gender specificity at the 95% confidence level and two others at 97.5% confidence. Because gender-related TAGs differences were most often close to the standard deviation of the measurements, the majority of the TAGs showed no gender specificity. Thus, LDI-TOF MS is not a reliable indicator of gender based on fingermark analysis. Cosmetic ingredients present in some samples were identified.
This article is available online at http://www.jlr.org where it is important to detect multiple lipid classes [i.e., phospholipids and triacylglycerols (TAGs)] include food analysis ( 1-3 ), cell biology ( 4 ), health effects ( 5 ), taxonomy ( 6 ), and other fi elds ( 7-11 ). However, because of different chemistries, it is often diffi cult to characterize one class of lipids in the presence of another, especially using rapid methods. Elegant methods have been developed for quantitative analysis in complex mixtures, but they are typically diffi cult to implement and are time consuming ( 8,12 ). There has been much recent interest in rapid MALDI-MS analysis of lipids due to its speed of analysis and high sensitivity ( 5,13,14 ). Sample preparation is quick because derivatization is not required (i.e., no silylation), HPLC separation is not needed, limited buffer or salt contamination is tolerated ( 9, 11, 13 ), and spectra are easy to interpret ( 13 ).MALDI-MS has functioned as both a qualitative and semiquantitative approach to measure and track effected biology-related phenomena. For example, Lay et al. ( 15 ) demonstrated a rapid method for the analysis of edible oils by MALDI-MS that allowed determination of the relative abundances of TAGs with suffi cient accuracy to correctly identify blind-coded samples of various oils. Gidden et al. ( 16 ) have also reported using MALDI-MS to rapidly differentiate Escherichia coli and Bacillus subtilis based on the phospholipid profi le and monitor changes in lipid content during the growth phases of the bacteria. However, this rapid MALDI-MS approach cannot currently be applied to experiments requiring the detection of multiple lipid classes in an unresolved mixture. Attempts to use direct MALDI-MS on such complex mixtures invariably results in entire classes of lipids being missed because of suppression effects.
JWH-018 (1-pentyl-3-(1-naphthoyl)indole) is one of numerous potential aminoalkylindoles contained in products marketed as ‘K2’ or ‘Spice’. Investigation of the urinary metabolites from consumption of these compounds is important because they are banned in the United States and many European countries. An efficient extraction procedure and gas chromatography – mass spectrometry (GC-MS) method were developed for detection of ‘K2’ metabolites in urine from individuals suspected of using these products. Analytical standards were used to elucidate the structure-specific mass spectral fragmentations and retention properties to confirm proposed identifications and support quantitative studies. A procedure for the synthesis of one of these metabolites (5-hydroxypentyl JWH-018) was also developed. Results are comparable to existing LC-MS/MS methods, with the same primary metabolites detected. The specific metabolite hydrolysis products include 4-hydroxpentyl, 5-hydroxypentyl, and N-pentanoic acid derivatives.
Several new methods have been developed recently that allow the direct detection of lipids without resorting to derivatization or chromatographic separation. The simplest of these is direct MALDI (matrix-assisted laser desorption/ionization) mass spectrometry. This approach is most useful for mixtures that contain minimal amounts of ion-suppressing interfering components. However, even when such components are present, their effects can often be minimized by using simple separation techniques beforehand, such as solid phase extraction or thin layer chromatography. For example, direct MALDI has been used for rapid screening of lipids and for taxonomic identification of the source organisms with no sample pretreatment. Fractions collected from solid phase extraction cartridges have also been used to avoid the most extreme effects of ion suppression from more complex lipid mixtures. More recently, direct MALDI has been applied to the analysis of TLC plates allowing the detection of TLC-separated lipids from the complex lipidome. Herein, we briefly describe the application of rapid MALDI MS to some typical research problems involving the characterization of lipids. In Part 1 these include bacterial taxonomy by direct analysis of intact lipids in simple extracts rather than by conversion to fatty acid methyl esters. Food oils such as triacylglycerols can be characterized simply and easily by direct MALDI MS without resort to any sort of separation. Part 2 (in the next issue of Lipid Technology) will cover the spontaneous fragmentation of protonated lipids, ion suppression and the use of solid phase extraction and thin layer chromatography with MALDI MS to characterize complex biological samples.
Several new methods have been developed recently that allow the direct detection of lipids without resorting to derivatization or chromatographic separation. The simplest of these is direct MALDI (matrix‐assisted laser desorption/ionization) mass spectrometry. This approach is most useful for mixtures that contain minimal amounts of ion‐suppressing interfering components. However, when such components are present, their effects can often be minimized by using simple separation techniques beforehand, such as solid phase extraction or thin layer chromatography. For example, direct MALDI has been used for rapid screening of lipids and taxonomic identification of the source organisms with no sample pretreatment. Collecting fractions from solid phase extraction cartridges have also been used to avoid the most extreme effects of ion suppression from more complex lipid mixtures. More recently, direct MALDI has been applied to the analysis of TLC plates allowing the detection of TLC‐separated lipids from the complex lipidome. Herein, we briefly describe the application of rapid MALDI MS to some typical research problems involving the characterization of lipids. In Part 1 [1] we covered bacterial taxonomy by direct analysis of intact lipids and the analysis of food oil triacylglycerols . Part 2 will address ion suppression, spontaneous fragmentation, and coupling MALDI with chromatography. The spontaneous fragmentation of protonated lipids in oils by direct MALDI produces artifactual diacylglycerol‐like ions. An understanding of this process and its minimization facilitates monitoring the decomposition of lipids by direct analysis. Suppression also has an impact on direct analysis of lipids, especially when mixtures contain both polar and non‐polar lipids. We demonstrate the use of solid phase extraction and thin layer chromatography to produce fractions or substrates from complex biological samples in which lipids can be detected by direct and rapid MALDI MS analysis.
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