MS/MS Research Articles

Identifying Challenges and Risks Associated with the Analysis of Major Mycotoxins in Feed and Botanicals.

Changing weather conditions have heightened the risk of growth of mycotoxigenic molds on crops and various agricultural commodities. Mycotoxins, which are linked to carcinogenic and nephrotoxic effects in animals and humans, have been traditionally analyzed by immunoassays, gas, and LC techniques with spectrophotometric detectors. This review discusses the current techniques and challenges in commercial settings associated with the analysis of mycotoxins in unique matrices such as animal feeds, herbal products, and dietary supplements containing botanicals. Because of the advantages and growing acceptance of LC-tandem MS (MS/MS) over traditional approaches, discussion is mainly based on LC-MS/MS-based approaches. Considering the impact of sample preparation on accuracy of quantitative results, discussion about pros and cons of recently introduced sample preparation techniques is integrated with analytical methods. A section of the review explains the importance and availability of reference materials for mycotoxins. The present discussion provides good insight into the current challenges and developments during mycotoxin analysis of feed and botanicals and addresses the need for researchers in terms of an official MS-based method.

FaPEx® Multipesticide Residues Extraction Kit for Minimizing Sample Preparation Time in Agricultural Produce

Background: The quick, easy, cheap, effective, rugged, and safe method, generally applied to the determination of pesticide residues in food, has been recently modified and adopted for the analysis of pesticide residues worldwide, including Taiwan. Objective: The method still needs to be improved, particularly in efficiency and normalization, because the time costs 20-30 min for extraction and cleanup of multiple pesticides in every food. Methods: In this study, we present a highly efficient and simple sample preparation method that was developed for the determination of 380 pesticide residues in food, including mangoes, scallions, bok choy, apples, carrots, and pea seedlings. The homogenized 1 g samples mixed with 5 mL 1.0% acetic acid in acetonitrile were pushed through the FaPEx® (fast pesticide extraction) kits in a dropwise manner to obtain sample extracts. The total processing time was less than 15 min. The extracts were subject to chromatographic separation followed by GC-tandem MS (MS/MS) and LC-MS/MS analysis. Results: For more than 270 pesticide residues in these foods, the test gave acceptable mean recoveries, ranging between 70 and 120%, and relative SDs below 20%. The LOQ was at least 0.01 mg/kg for 380 pesticides. Conclusions: The developed method can greatly reduce the time needed for multiple pesticide residues analysis. Highlights: FaPEx is used for the extraction of pesticide residues that relies on single-use pre-filled sealed cartridges. FaPEx diminishes operation time, glassware demand, and laboratory space requirement. It also significantly decreases the amount of chemical solvents.

Mycotoxin Testing Paradigm: Challenges and Opportunities for the Future

Mycotoxins are one of the great global challenges to agri-food and feed safety. Industry requires fast, reliable, and economical testing methods for the most important regulated mycotoxins to manage this problem. Climate change and changes in agricultural practice are complicating this situation, triggering the movement of some mycotoxins into new regions, which are unprepared for their management. Modern LC-tandem MS (LC-MS/MS) instruments have addressed this analytical challenge, but such instruments are expensive and require highly qualified personnel and dedicated facilities. As a result of these limitations, traditional LC-MS/MS is not amenable for use on farms or at small to midsized processing facilities, such as a grain elevator. To address the need for on-site rapid testing, the mycotoxin community has focused on antibody-based and spectrophotometric approaches. The development of innovative technologies such as miniaturized MS would allow for the acquisition of more information on mixtures of toxins present in a sample at costs comparable to those of the existing rapid methods such as ELISA. The capital costs are higher, but it would reduce per-sample testing costs and time requirements and provide better value for money while maintaining the accuracy and selectivity achieved in a laboratory setting. In this article, we review the available techniques and contrast them in the context of three main criteria: method performance, speed of analysis, and cost. We define the integration of these three parameters as the "mycotoxin testing paradigm."

Isotope dilution LC-orbitrap-HRMS with automated sample preparation for the simultaneous quantification of 11 antimycotics in human serum

IntroductionThe aim of this project was to develop and validate an isotope-dilution liquid chromatography high resolution mass spectrometry (LC-HRMS) method for the quantification of the 11 most widely used systemic antimycotics and to study whether HRMS is a feasible alternative for therapeutic drug monitoring (TDM) when compared to tandem MS (MS/MS) technology. MethodsAfter protein precipitation, followed by automated online sample clean-up the analytes were separated within 4 min on a C18 column using an acetonitrile-water gradient. Eleven antimycotics, namely 5-flucytosine, amphotericin B, anidulafungin, fluconazole, isavuconazole, itraconazole, ketoconazole, micafungin, OH-itraconazole, posaconazole and voriconazole were finally quantified in full MS scan mode using positive electrospray ionization (ESI +) with a mass range fromm/z 110–1300 using HRMS. The method was comprehensively validated on the basis of the European Medicines Agengy (EMA) method validation protocol using commercially available IVD kit components. ResultsGood linear relationship between peak area responses and drug concentrations (R2 > 0.995) and excellent selectivity were observed for all antimycotics in this study. Inaccuracy and imprecision of all quality controls were consistently below ± 12.6% and ± 8.1%, respectively. Quantification results were in agreement with an IVD LC–MS/MS method. ConclusionHRMS was shown to be suitable for TDM of small molecules when compared to tandem mass spectrometry. The novel HRMS method is quickly installed and may be a robust and reliable tool for routine TDM of antimycotics in clinical laboratories.

An Assay on Alkyl Aromatic Hydrocarbons: Unexpected Group-Type Separation of Diaromatic Hydrocarbons in Cretaceous Crude Oils from Brazilian Marginal Basin

Numerous aromatic biomarkers such as aromatic carotenoids and aryl isoprenoids have been reported in Brazilian Cretaceous oils. The n-alkyl aromatics such as n-alkyl benzenes (ϕ-Cn), toluenes (ϕT-Cn), xylenes, and mesitylenes have also been detected in geological samples and can be valuable tools in geochemical and environmental investigations. In this work, comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOFMS) and GC–tandem MS (GC–MS/MS) were applied to identify the alkyl aromatic series in two crude oils from the Sergipe-Alagoas Basin, Brazil. Geochemical characteristics indicate a different depositional paleoenvironment for each sample, marine and lacustrine end-members. Aromatic compounds were identified using full mass spectrum information, diagnostic ions (i.e., m/z 92 for alkylbenzenes and m/z 106 for alkyltoluenes), selected reaction monitoring transitions, and coinjection with an authentic C21 n-pentadecylbenzene standard. The Sergipe-Alagoas o...

Mass Spectrometry Measurement of Single Suspended Cells Using a Combined Cell Manipulation System and a Single-Probe Device.

Existing single cell mass spectrometry (SCMS) sampling platforms are largely designed to work only with immobilized cells and not the suspended cells isolated from patient samples. Here, we present a novel method that integrates a commercially available cell manipulation system commonly used for in vitro fertilization with the Single-probe SCMS sampling technology. The combined Single-probe SCMS/cell manipulating platform is capable of rapidly analyzing intracellular species in real time from a suspension leukemia cell line. A broad range of molecular species was detected, and species of interest were verified using tandem MS (MS/MS). Experimental results were analyzed utilizing statistical analyses such as principle component analysis (PCA) and t-tests. The developed SCMS/cell manipulation system is a versatile tool to provide rapid single cell analysis of broad types of patient cell samples.

An LC-MS profiling method reveals a route for apocarotene glycosylation and shows its induction by high light stress in Arabidopsis.

Apocarotenoid glycosylation serves as a valve regulating carotenoid homeostasis in plants and may contribute to their response to photo-oxidative stress. However, an analytical method that allows comprehensive and sensitive profiling of glycosylated apocarotenoids (GAPOs) is still missing. We developed an efficient ultra-high performance liquid chromatography-high resolution-mass spectrometry (UHPLC-HR-MS) method to analyze 25 GAPOs present in carotenoid-accumulating E. coli cells and plant tissues. Optimized HR-heated-electrospray ionization (HESI)-MS parameters enabled, based on HR MS and tandem mass spectrometry (MS/MS) data, the identification of yet undescribed GAPOs from Arabidopsis, which include Glc-apo-11-carotenal (GAPO11), Glc-apo-13-carotenone (GAPO13), and their isomers. The identity of these compounds was confirmed by the transformation of deuterium-labelled non-hydroxylated carotene cleavage products into the corresponding GAPOs in planta. Quantitative analysis of GAPOs in Arabidopsis showed that the levels of Glc-cyclocitral (GAPO7), Glc-cyclocitral isomer I (GAPO7I), Glc-ionone (GAPO9), Glc-ionone isomer I (GAPO9I), Glc-apo-11-carotenal isomer I (GAPO11I), Glc-apo-13-carotenone (GAPO13), and Glc-apo-13-carotenone isomers (GAPO13I, GAPO13II, and GAPO13III) significantly increase after high light (HL) treatment. This treatment also led to an obvious increase in the levels of most carotene- and all xanthophyll-derived apocarotenoids detected in our system. Our work demonstrates for the first time that HL stress induces apocarotenoid glycosylation in Arabidopsis and unravels a novel plant metabolic pathway that leads from carotene cleavage products to GAPOs that are identical to xanthophyll derived GAPOs. Thus, our new approach allows sensitive and reliable profiling of GAPOs, which is crucial for understanding the function of apocarotenoid glycosylation in plants and its role in the acclimation to HL stress.

Top-Down and Intact Protein Mass Spectrometry Data Visualization for Proteoform Analysis Using VisioProt-MS.

The rise of intact protein analysis by mass spectrometry (MS) was accompanied by an increasing need for flexible tools allowing data visualization and analysis. These include inspection of the deconvoluted molecular weights of the proteoforms eluted alongside liquid chromatography (LC) through their representation in three-dimensional (3D) liquid chromatography coupled to mass spectrometry (LC-MS) maps (plots of deconvoluted molecular weights, retention times, and intensity of the MS signal). With this aim, we developed a free and open-source web application named VisioProt-MS (https://masstools.ipbs.fr/mstools/visioprot-ms/). VisioProt-MS is highly compatible with many algorithms and software developed by the community to integrate and deconvolute top-down and intact protein MS data. Its dynamic and user-friendly features greatly facilitate analysis through several graphical representations dedicated to MS and tandem mass spectrometry (MS/MS) analysis of proteoforms in complex samples. Here, we will illustrate the importance of LC-MS map visualization to optimize top-down acquisition/search parameters and analyze intact protein MS data. We will go through the main features of VisioProt-MS using the human proteasomal 20S core particle as a user-case.

Top-down and middle-down proteomic analysis of Shiga toxin using MALDI-TOF-TOF mass spectrometry

The method describes a step-by-step process for analysis of putative Shiga toxin-producing Escherichia coli (STEC) for expression of Shiga toxin (Stx). The technique utilizes antibiotic induction, mass spectrometry and top-down/middle-down proteomic analysis. Stx expression is induced by overnight culturing of a STEC strain on Luria-Bertani agar (LBA) supplemented with DNA-damaging antibiotics. Culturing on agar media avoids sample contamination from salts, small molecules, peptides, etc. present in broth media that would interfere with protein ionization by matrix-assisted laser desorption/ionization (MALDI). No mechanical lysis of bacterial cells is required to release the toxin as the antibiotic triggers the lytic cycle of the bacteriophage resulting in toxin expression and bacterial cell lysis. Unfractionated samples are analyzed by MALDI-time-of-flight-time-of-flight (MALDI-TOF-TOF) mass spectrometry and tandem mass spectrometry (MS/MS) using post-source decay (PSD). New features of the method are the following.•Each putative STEC strain is systematically screened for toxin expression using two different antibiotics at two different concentrations: ciprofloxacin at 10 and 20 ng mL−1 and mitomycin-C at 800 and 1200 ng mL−1 to determine the optimal antibiotic and concentration for toxin expression for each strain.•The grid-to-source voltage of MALDI-TOF-TOF is optimized to maximize PSD efficiency.

Profile of Phosphatidylserine Modifications under Nitroxidative Stress Conditions Using a Liquid Chromatography-Mass Spectrometry Based Approach.

Nitrated lipids have been detected in vitro and in vivo, usually associated with a protective effect. While nitrated fatty acids have been widely studied, few studies reported the nitration and nitroxidation of the phospholipid classes phosphatidylcholine, and phosphatidylethanolamine. However, no information regarding nitrated and nitroxidized phosphatidylserine can be found in the literature. This work aims to identify and characterize the nitrated and nitroxidized derivatives of 1-palmitoyl-2-oleoyl-sn-3-glycero-phosphoserine (POPS), obtained after incubation with nitronium tetrafluoroborate, by liquid chromatography (LC) coupled to mass spectrometry (MS) and tandem MS (MS/MS). Several nitrated and nitroxidized products were identified, namely, nitro, nitroso, nitronitroso, and dinitro derivatives, as well as some nitroxidized species such as nitrosohydroxy, nitrohydroxy, and nitrohydroperoxy. The fragmentation pathways identified were structure-dependent and included the loss of HNO and HNO2 for nitroso and nitro derivatives, respectively. Combined losses of PS polar head group plus HNO or HNO2 and carboxylate anions of modified fatty acyl chain were also observed. The nitrated POPS also showed antiradical potential, demonstrated by the ability to scavenge the ABTS●+ and DPPH● radicals. Overall, this in vitro model of nitration based on LC-MS/MS provided additional insights into the nitrated and nitroxidized derivatives of PS and their fragmentation fingerprinting. This information is a valuable tool for targeted analysis of these modified PS in complex biological samples, to further explore the new clues on the antioxidant potential of nitrated POPS.

Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry and Tandem Mass Spectrometry. 4. 3-Ring and 4-Ring Isomers

Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) is used to characterize methylenedianiline (MDA) 3-ring and 4-ring species. Building on our previous MALDI-MS 2-ring MDA isomer study, here we compare 3-ring and 4-ring electrospray ionization (ESI) and MALDI results. In ESI, 3-ring and 4-ring MDAs each form a single [M + H]+ parent ion. However, in MALDI, each MDA multimer forms three unique precursor ions: [M + H]+, [M•]+, and [M - H]+. In this study, 3-ring and 4-ring MDA precursors are characterized to identify the unique fragment ions formed and their respective fragmentation pathways. In addition to the three possible precursors, the 3-ring and 4-ring species are higher-order oligomer precursors in polyurethane (PUR) production and thus provide additional insight into the polymeric behavior of these PUR hard block precursors. The combination of ion mobility-mass spectrometry (IM - MS) and tandem mass spectrometry (MS/MS) allow the structural characterization of these larger MDA multimers.

Correlating In-Depth Mechanistic Understanding with Mechanical Properties of High-Temperature Resistant Cyclic Imide Copolymers

We break new ground in the in-depth mechanistic understanding of the molecular behavior of tert-butyl methacrylate (t-BMA) and N-isopropylacrylamide (NIPAM) copolymers upon thermal treatment and correlate this understanding with the mechanical properties of the resulting materials. We explore—via nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic measurements—the formation of cyclic anhydride and imide structures and exploit high-resolution mass spectrometry (HRMS) coupled to size-exclusion chromatography (SEC) as well as tandem MS (MS/MS) to correlate the time and temperature dependent cyclization processes. Critically, we propose a reshuffling mechanism describing dynamic ring-opening events involving the anhydride and imide structures, which enables the in-depth understanding of the dynamic material properties. Drawing on information from low-molecular-weight model systems, we translate our findings to high-molar-mass polymers, showing that our mechanistic model enables the understanding ...

Hydrogen-Deuterium Exchange Coupled to Top- and Middle-Down Mass Spectrometry Reveals Histone Tail Dynamics before and after Nucleosome Assembly

Until recently, a major limitation of hydrogen-deuterium exchange mass spectrometry (HDX-MS) was that resolution of deuterium localization was limited to the length of the peptide generated during proteolysis. However, electron transfer dissociation (ETD) has been shown to preserve deuterium label in thegas phase, enabling better resolution. To date, this technology remains mostly limited to small, already well-characterized proteins. Here, we optimize, expand, and adapt HDX-MS tandem MS (MS/MS) capabilities to accommodate histone and nucleosomal complexes on top-down HDX-MS/MSand middle-down HDX-MS/MS platforms and demonstrate that near site-specific resolution of deuterium localization can be obtained with high reproducibility. We are able to study histone tail dynamics in unprecedented detail, which have evaded analysis by traditional structural biology techniques for decades, revealing important insights into chromatin biology. Together, the results of these studies highlight the versatility, reliability, and reproducibility of ETD-based HDX-MS/MS methodology to interrogate large protein and protein/DNA complexes.

A lipidomic perspective on the embryogenesis of two commercially important crabs, Carcinus maenas and Necora puber

Lipids play a central role in the metabolism of most organisms. These molecules are paramount during reproduction, when females transfer their internal lipid reserves to build-up oocytes' yolk. The aim of the present study was to understand neutral lipid (NL) dynamics during the embryogenesis of two commercially important crabs, Carcinus maenas (Linnaeus, 1758) and Necora puber (Linnaeus, 1767), using electrospray ionization mass spectrometry (ESI–MS) and tandem MS (ESI–MS/MS). Total lipid extracts were fractionated into NLs and polar lipids (PLs). Triacylglycerol (TAG) profile of NL and fatty acid (FA) profiles of both NLs and PLs were determined in two different embryonic stages: newly-extruded embryos (stage 1, a proxy of maternal investment) and ready-to-hatch embryos (stage 3, a proxy of newly-hatched larvae). In total, 16 molecular species of TAGs and their fatty acyl composition were identified, for the first time in marine invertebrate embryos. During embryogenesis, TAGs bearing C14 to C18 saturated and monounsaturated FAs were preferentially consumed, while TAGs with longer carbon chains and polyunsaturated FAs were selectively retained in the late embryonic stage of both crab species. The analysis of FA profiles revealed that energetic FAs were associated with NLs, while essential FAs were more abundant in PLs. These results evidence the different functions of NLs and PLs as energetic and structural lipids, respectively. The novel approach used in our study provides an unprecedented level of information of lipid dynamics at the molecular level, opening new perspectives in the study of maternal investment and embryogenesis in marine invertabrates.

Metabolic perturbations associated with the consumption of a ketogenic medium-chain TAG diet in dogs with idiopathic epilepsy

Consumption of diets containing medium-chain TAG (MCT) has been shown to confer neuroprotective effects. We aim to identify the global metabolic perturbations associated with consumption of a ketogenic diet (medium-chain TAG diet (MCTD)) in dogs with idiopathic epilepsy. We used ultra-performance liquid chromatography-MS (UPLC-MS) to generate metabolic and lipidomic profiles of fasted canine serum and made comparisons between the MCTD and standardised placebo diet phases. We identified metabolites that differed significantly between diet phases using metabolite fragmentation profiles generated by tandem MS (UPLC-MS/MS). Consumption of the MCTD resulted in significant differences in serum metabolic profiles when compared with the placebo diet, where sixteen altered lipid metabolites were identified. Consumption of the MCTD resulted in reduced abundances of palmitoylcarnitine, octadecenoylcarnitine, stearoylcarnitine and significant changes, both reduced and increased abundances, of phosphatidylcholine (PC) metabolites. There was a significant increase in abundance of the saturated C17 : 0 fatty acyl moieties during the MCTD phase. Lysophosphatidylcholine (17 : 0) (P=0·01) and PC (17:0/20:4) (P=0·03) were both significantly higher in abundance during the MCTD. The data presented in this study highlight global changes in lipid metabolism, and, of particular interest, in the C17 : 0 moieties, as a result of MCT consumption. Elucidating the global metabolic response of MCT consumption will not only improve the administration of current ketogenic diets for neurological disease models but also provides new avenues for research to develop better diet therapies with improved neuroprotective efficacies. Future studies should clarify the involvement and importance of C17 : 0 moieties in endogenous MCT metabolic pathways.

Multimycotoxin Analysis by LC-MS/MS in Cereal Food and Feed: Comparison of Different Approaches for Extraction, Purification, and Calibration

Twelve different approaches commonly used for the simultaneous LC tandem MS (MS/MS) determination of mycotoxins (deoxynivalenol, aflatoxins, ochratoxin A, T-2 and HT-2 toxins, fumonisins, and zearalenone) were tested in cereals and feed materials. They comprised different extraction solvents, types of cleanup [solid-phase extraction, QuEChERS, and immunoaffinity (IMA)], and calibration approaches (external or matrix-matched). The percentage of mycotoxins with acceptable recovery, according to Regulation (EC) No. 401/2006, ranged from 9 to 100%. The approach giving the highest percentage of acceptable results was selected and further tested for corn, rice, and feed spiked at three different mycotoxin levels (low, medium, and high). The method is based on extraction with MeOH-water (70 + 30, v/v) and cleanup with two multiantibody IMA columns. For corn and rice spiked at low mycotoxin levels, a significant matrix effect was observed and was compensated by using 13C calibration. At higher mycotoxin levels (medium and high), matrix effects were negligible as no significant differences were observed for the majority of recovery results calculated by 13C calibration and external calibration. Although the proposed method still needs improvement in terms of accuracy and, to a lesser extent, precision, it was successfully tested with four proficiency tests in buckwheat, corn, rice, and feed, giving acceptable z-scores for 97% (34 out of 35) of results.

Ultra-High-Performance Supercritical Fluid Chromatography as a Separation Tool for Fusarium Mycotoxins and Their Modified Forms.

A simple, reliable method for the detection of free and modified Fusarium mycotoxins in beer using state-of-the-art ultra-high-performance supercritical fluid chromatography (UHPSFC) with low-resolution tandem MS (MS/MS) is presented in this paper. The UHPSFC-MS/MS method was developed for nivalenol, deoxynivalenol, 15-acetyl-deoxynivalenol, 3-acetyl-deoxynivalenol, deoxynivalenol-3-glucoside, HT-2 toxin, T-2 toxin, T-2 toxin-3-glucoside, neosolaniol, diacetoxyscirpenol, zearalenone, α-zearalenol, and β-zearalenol and their internal standards deepoxy-deoxynivalenol and zearalanone. Due to the broad range of the physicochemical properties of the aforementioned, the sample preparation step was minimized to avoid analyte losses. Extraction with acetonitrile-water-acetic acid (79 + 20 + 1, v/v/v) and hexane in combination with solid-phase extraction (C18) was followed by a filtration step. After filtration, the extract was evaporated, and the remaining residue was redissolved in a mobile phase for injection (methanol-water; 90 + 10, v/v). A mobile phase consisting of supercritical CO2 and a small portion of methanol was used. The developed multimycotoxin method permits the simultaneous determination of multiple fusariotoxins in an one-step chromatographic run using UHPSFC-MS/MS. SFC is a promising strategy; however, the retention mechanism is complex, leading to the unpredictable nature of elution and to some mycotoxins not being retained on the column. This restricts the applicability of UHPSFC in multimycotoxin analyses. The present study is the first report on the use of UHPSFC for the analysis of free and modified Fusarium mycotoxins.

Proteomic profiling of exosomes leads to the identification of novel biomarkers for prostate cancer progression

Exosomes are vesicles which have garnered interest due to their diagnostic and therapeutic potential. Isolation of cancer‐derived exosomes is a prerequisite for their better understanding. We have investigated a new biomarker for prostate cancer progression via quantitative proteomics. Exosomes from androgen‐independent PC‐3 and the androgen‐dependent LNCaP prostate cancer cells were isolated by ultracentrifugation. After tryptic digestion, proteomic analyses utilized a nanoLC coupled with an LTQ‐Orbitrap operated in tandem MS (MS/MS) mode. Accurate Mass and Time (AMT) tag approach was employed for peptide identification and quantitation. Proteomic characterization showed that 105 proteins from PC‐3 exosomes were 10‐fold higher than those from LNCap. Validation by Western blotting and qRT‐PCR confirmed a higher abundance of PFKL, NRP1 and MCAM(CD146) in PC‐3 cell exosomes, too, indicating that aggressive prostate cancer exhibit higher levels of adhesion or cohesion proteins. We also show that MCAM (CD146) was strongly associated to PC‐3 mobility in vitro. These data provided that MCAM should be useful as a new candidate biomarker for prostate cancer progression.Support or Funding InformationThis work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) (OGM4391711)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Rapid Characterization of Triacylglycerols in Edible Oils by Matrix-assisted Laser Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Abstract Composition and types of triacylglycerols (TAGs) in edible oils are closely related to our health. It is of vital significance to develop fast and high-efficiency methods for determination of TAGs. In this manuscript, qualitative analysis of TAGs was demonstrated using matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS). 2,5-Dihydroxybenzoic acid (DHB) was employed as matrix and dichloromethane was used as solvent for dissolving the edible oils. With laser power of 15%, laser frequency of 100 Hz, and 100 laser shots, relative standard deviation (RSD) less than 9% was obtained. Different kinds of edible oils could be directly distinguished from each other using MS and tandem MS (MS/MS) results. With confidence level of 95%, principal component analysis (PCA) results showed that 34 different kinds of edible oils were clearly classified. Moreover, down to 5% of doped canola in olive was identified directly, indicating that MALDI-FTICR-MS has the potential for rapid analysis and screening of edible oils.

Formation and Occurrence of Iodinated Tyrosyl Dipeptides in Disinfected Drinking Water.

Iodinated disinfection byproducts (I-DBPs) are highly toxic, but few precursors of I-DBPs have been investigated. Tyrosine-containing biomolecules are ubiquitous in surface water. Here we investigated the formation of I-DBPs from the chloramination of seven tyrosyl dipeptides (tyrosylglycine, tyrosylalanine, tyrosylvaline, tyrosylhistidine, tyrosylglutamine, tyrosylglutamic acid, and tyrosylphenylalanine) in the presence of potassium iodide. High resolution mass spectrometry and tandem mass spectrometry (MS/MS) analyses of the benchtop reaction solutions found that all seven precursors formed both I- and Cl-substituted tyrosyl dipeptide products. Iodine substitutions occurred on the 3- and 3,5-positions of the tyrosyl-phenol ring while chlorine substituted on the free amino group. To reach the needed sensitivity to detect iodinated tyrosyl dipeptides in authentic waters, we developed a high performance liquid chromatography (HPLC)-MS/MS method with multiple reaction monitoring mode and solid phase extraction. HPLC-MS/MS analysis of tap and corresponding raw water samples, collected from three cities, identified four iodinated peptides, 3-I-/3,5-di-I-Tyr-Ala and 3-I-/3,5-di-I-Tyr-Gly, in the tap waters but not in the raw waters. The corresponding precursors, Tyr-Ala and Tyr-Gly, were also detected in the same tap and raw water samples. This study demonstrates that iodinated dipeptides exist as DBPs in drinking water.