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The Paternò-Büchi (PB) derivatization of carbon-carbon double bond (C═C) has been increasingly employed with tandem mass spectrometry to analyze unsaturated lipids. It enables the discovery of altered or uncanonical lipid desaturation metabolism, which would be otherwise undetected by conventional methods. Although highly useful, the reported PB reactions only provide moderate yield (∼30%). Herein, we aim to determine the key factors that affect the PB reactions and develop a system with improved capabilities for lipidomic analysis. An Ir(III) photocatalyst is chosen as the triplet energy donor for the PB reagent under 405 nm light irradiation, while phenylglyoxalate and its charge-tagging version, pyridylglyoxalate, are developed as the most efficient PB reagents. The above visible-light PB reaction system provides higher PB conversions than all previously reported PB reactions. Around 90% conversion can be achieved at high concentrations (>0.5 mM) for different classes of lipids but drops as the lipid concentration decreases. The visible-light PB reaction has then been integrated with shotgun and liquid chromatography-based workflows. The limits of detection for locating C═C in standard lipids of glycerophospholipids (GPLs) and triacylglycerides (TGs) are in the sub-nM to nM range. More than 600 distinct GPLs and TGs have been profiled at the C═C location level or the sn -position level from the total lipid extract of bovine liver, demonstrating that the developed method is capable of large-scale lipidomic analysis.

Mass spectrometry imaging (MSI) of lipids in biological tissues is useful for correlating molecular distribution with pathological results, which could provide useful information for both biological research and disease diagnosis. It is well understood that the lipidome could not be clearly deciphered without tandem mass spectrometry analysis, but this is challenging to achieve in MSI due to the limitation in sample amount at each image spot. Here we develop a multiplexed MS 2 imaging (MS 2 I) method that can provide MS 2 images for 10 lipid species or more for each sampling spot, providing spatial structural lipidomic information. Coupling with on-tissue photochemical derivatization, imaging of 20 phospholipid C=C location isomers is also realized, showing enhanced molecular images with high definition in structure for mouse brain and human liver cancer tissue sections. Spatially mapped t-distributed stochastic neighbor embedding has also been adopted to visualize the tumor margin with enhancement by structural lipidomic information., (© 2022 Wiley-VCH GmbH.)

The reliable identification of fentanyl and its analogs is of great significance for public security. However, with the growing prevalence of fentanyl compounds, current analytical strategies cannot fully meet the need for fast and high-throughput detection. In this study, a simple, rapid, and on-site analytical protocol was developed based on a miniature mass spectrometer. A dramatically simplified workflow was implemented using matrix-assisted ionization, bypassing complex sample pretreatment and chromatographic separation. The tandem mass spectrometry (MS/MS) capability afforded by the miniature ion trap mass spectrometer facilitated the investigation of fragmentation patterns for 49 fentanyl analogs during collision-induced dissociation, revealing valuable information on marker fragment ions and characteristic neutral loss. Calculations on Laplacian bond order values further verified the mass spectrometric behavior. A computation-assisted expandable mass spectral library was constructed in-house for fentanyl compounds. Smart suspect screening was carried out based on the full-scan MS and MS/MS data. The present study demonstrates an appealing potential for forensic applications, enabling streamlined screening for the presence of illicit fentanyl compounds at the point of seizures of suspect samples.

An analytical methodology for comprehensive screening of 63 coloring agents of great concern for regulatory control in cosmetics has been established using ultra-high-performance liquid chromatography (UHPLC) coupled with quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS). An effective, rapid, and simple sample pretreatment protocol with low sample and reagent consumption was developed based on matrix solid-phase dispersion (MSPD). The selection of the most suitable extraction conditions was made using statistical tools of factorial multifactor experimental design and analysis of variance (ANOVA). In the final conditions, 0.1 g of cosmetic sample was blended with 0.3 g of anhydrous sodium sulfate and 0.4 g of sand, and the MSPD column was eluted with 2 mL of methanol. The extract was analyzed by UHPLC-Q-Orbitrap HRMS under synchronous full-scan MS and data-dependent MS/MS (full-scan MS 1 /dd-MS 2 ) acquisition mode. The mass resolution was set to 70,000 FWHM (full width at half maximum) for full-scan MS 1 and 17,500 FWHM for dd-MS 2 stage with the experimentally measured mass deviations of less than 3 ppm (parts per million) for quasi-molecular ions and 5 ppm for characteristic fragment ions for each individual analyte. An accurate-mass database and a mass spectral library were built in house for searching the 63 target compounds. Broad screening was conducted by comparing the experimentally measured exact mass of precursor and fragment ions, retention time, isotopic pattern, and ionic ratio with the accurate-mass database and by matching the acquired MS/MS spectra against the mass spectral library. Method performance was evaluated in terms of limits of detection (LODs), limits of quantitation (LOQs), linearity, precision, recovery, and matrix effect. The UHPLC-Q-Orbitrap HRMS approach was applied for the simultaneous analysis of 63 target coloring agents in 69 genuine cosmetic samples. Eleven legally prohibited coloring agents were detected in 26 cosmetic samples in total. The proposed method exhibited great potential for high-throughput, sensitive, and reliable screening of multi-class coloring agent substances in cosmetics., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Objective: A rapid analytical method had been developed for the screening of three halogenated salicylanilines in cosmetics using ambition ionization coupled with ion mobility spectrometry., Methods: Without time-consuming pretreatment, cosmetic samples of lotion, lipstick and powder were added or smudged onto a Grade 3MM chromatography paper for paper spray ionization, cosmetic samples of cream and shampoo were simply loaded with a metal wire probe for extraction nano-electrospray., Results: The limits of detection( LODs) for the three halogenated salicylanilides were 50 μg/kg. The instrumental analysis time for a single ion mobility spectrometry run was less than 15 ms. The suspected positive samples were subjected to further verification by high-performance liquid chromatography coupled with tandem mass spectrometry., Conclusion: The method is simple, rapid, and with low cost and is suitable for rapid, on-site screening of cosmetics.

Spatial lipidomics based on mass spectrometry imaging (MSI) is a powerful tool for fundamental biology studies and biomarker discovery. But the structure‐resolving capability of MSI is limited because of the lack of multiplexed tandem mass spectrometry (MS/MS) method, primarily due to the small sample amount available from each pixel and the poor ion usage in MS/MS analysis. Here, we report a mobility‐modulated sequential dissociation (MMSD) strategy for multiplex MS/MS imaging of distinct lipids from biological tissues. With ion mobility‐enabled data‐independent acquisition and automated spectrum deconvolution, MS/MS spectra of a large number of lipid species from each tissue pixel are acquired, at no expense of imaging speed. MMSD imaging is highlighted by MS/MS imaging of 24 structurally distinct lipids in the mouse brain and the revealing of the correlation of a structurally distinct phosphatidylethanolamine isomer (PE 18 : 1_18 : 1) from a human hepatocellular carcinoma (HCC) tissue. Mapping of structurally distinct lipid isomers is now enabled and spatial lipidomics becomes feasible for MSI. [ABSTRACT FROM AUTHOR]

A streamlined analytical workflow was developed for the analysis of infant drink samples using a miniature mass spectrometry system preceded by solid-phase microextraction (SPME) and extraction nano-electrospray ionization. Potential chemical contaminants in infant drinks (milk, lactic acid bacteria beverage, and fruit juice) were extracted and enriched using a custom-made stainless-steel SPME probe, which was coated with a thin layer of polyaniline and multi-walled carbon nanotubes nanocomposites (PANI/MWCNTs) by electrochemical deposition. The resulting porous microstructure has a larger surface area and enhanced microextraction efficiency, with enrichment factors ranging from 3055 to 8695 for exemplary analytes of antibiotics, bisphenol A, and perfluorinated compounds. The enriched analytes on the electrochemically fabricated SPME probe were simultaneously desorbed and ionized within a pulled glass capillary by extraction nano-electrospray ionization. The ionized species were subjected to instrumental analysis on a miniature ion trap mass spectrometer with adequate tandem mass spectrometry capability. The developed method was optimized and validated in terms of sensitivity, linearity, repeatability, and recovery. The integrated experimental protocol combining SPME, ambient ionization, and miniature mass spectrometry is promising for rapid, on-site screening of hazardous substances in food to ensure consumer health. Image 1 • A streamlined protocol combining solid-phase microextraction and miniature mass spectrometry analysis. • A custom-made solid-phase microextraction probe coated with polyaniline and multi-walled carbon nanotubes nanocomposites. • Direct, on-site identification of potential chemical pollutants in infant drinks. [ABSTRACT FROM AUTHOR]