Precursor Ion Research Articles

Simultaneous Determination of Nine Phthalates in Vegetable Oil by Atmospheric Pressure Gas Chromatography with Tandem Mass Spectrometry (APGC-MS/MS).

Although the use of phthalates has been restricted worldwide, they remain an issue due to health concerns. Diet is one of the most important exposure pathways for humans and due to their solubility in oil, phthalates are commonly found in edible oil and food high in fat. Gas chromatography-mass spectrometry (GC-MS) using electron ionization (EI) has been commonly used for the analysis of the phthalates in foodstuffs, including edible oil. However, this method suffers from issues with sensitivity and selectivity, as most phthalates are fragmented to generate a common phthalic anhydride fragment ion at m/z 149. The molecular ion cannot be observed due to strong fragmentation in EI. In contrast, atmospheric pressure gas chromatography (APGC) is a soft ionization technique with less fragmentation, whereby the molecular ion can be used as the precursor ion for multiple reaction monitoring (MRM). In this study, a simple and quick method for the determination of phthalates in vegetable oil using APGC-MS/MS was developed, and performance was assessed. The method was based on dilution of the oil in solvent and direct injection without the need for further cleanup. The established method was evaluated for linearity, recovery, precision, method detection limit (MDL), and method quantitation limit (MQL). The obtained MQL in vegetable oil was in the range of 0.015-0.058 mg/kg, despite limiting the injection volume to 1 µL, which is suitable for investigating dietary exposure and future proof against decreases to the regulatory limit. Finally, the developed method was successfully applied to analyze nine phthalates in eight commercially available vegetable oil.

Unraveling the Steric Link to Copper Precursor Decomposition: A Multi-Faceted Study for the Printing of Flexible Electronics.

The field of printed electronics strives for lower processing temperatures to move toward flexible substrates that have vast potential: from wearable medical devices to animal tagging. Typically, ink formulations are optimized using mass screening and elimination of failures; as such, there are no comprehensive studies on the fundamental chemistry at play. Herein, findings which describe the steric link to decomposition profile: combining densityfunctionaltheory, crystallography, thermal decomposition, mass spectrometry, and inkjet printing, are reported. Through the reaction of copper(II) formate with excess alkanolamines of varying steric bulk, tris-co-ordinated copper precursor ions: "[CuL3 ]," each with a formate counter-ion (1-3) are isolated and their thermal decomposition mass spectrometry profiles are collected to assess their suitability for use in inks (I1-3 ). Spin coating and inkjet printing of I1,2 provides an easily up-scalable method toward the deposition of highly conductive copper device interconnects (ρ = 4.7-5.3 × 10-7 Ω m; ≈30% bulk) onto paper and polyimide substrates and forms functioning circuits that can power light-emitting diodes. The connection among ligand bulk, coordination number, and improved decomposition profile supports fundamental understanding which will direct future design.

Major benznidazole metabolites in patients treated for Chagas disease: Mass spectrometry-based identification, structural analysis and detoxification pathways

Benznidazole is the drug of choice for the treatment of Chagas disease, but its metabolism in humans is unclear. Here, we identified and characterized the major benznidazole metabolites and their biosynthetic mechanisms in humans by analyzing the ionic profiles of urine samples from patients and untreated donors through reversed-phase UHPLC-ESI-QTOF-MS and UHPLC-ESI-QqLIT-MS. A strategy for simultaneous detection and fragmentation of characteristic positive and negative ions was employed using information-dependent acquisitions (IDA). Selected precursor ions, neutral losses, and MS3 experiments complemented the study. A total of six phase-I and ten phase-II metabolites were identified and structurally characterized in urine of benznidazole-treated patients. Based on creatinine-corrected ion intensities, nitroreduction to amino-benznidazole (M1) and its subsequent N-glucuronidation to M5 were the main metabolic pathways, followed by imidazole-ring cleavage, oxidations, and cysteine conjugations. This extensive exploration of benznidazole metabolites revealed potentially toxic structures in the form of glucuronides and glutathione derivatives, which may be associated with recurrent treatment adverse events; this possibility warrants further exploration in future clinical trials. Incorporation of this knowledge of the benznidazole metabolic profile into clinical pharmacology trials could lead to improved treatments, facilitate the study of possible drug-drug interactions, and even mitigation of adverse drug reactions.

Automated desorption electrospray ionization two-dimensional tandem mass spectrometry: Instrumentation and software for high throughput analysis

Two-dimensional tandem mass spectrometry (2D-MS/MS) provides rapid unsupervised access to all product ions of all ionized precursor ions. In this study, desorption electrospray ionization is used to create ion populations from complex mixtures prior to the use of 2D MS/MS to characterize each sample in an array. Automated high-throughput examination of each sample in the array is achieved by integrating movement of the sample array with automated acquisition of data from each sample through a serial handshake procedure. Position control is achieved using an Arduino microprocessor, a RAMPS control board, two stepper motors, and a custom MATLAB graphical user interface. Data processing improvements to the 2D-MS/MS workflow included optimizing the contrast of the intensity distribution of individual precursor to product ion transitions in local regions of the 2D spectrum to enhance visual discrimination of peaks from the background. This study demonstrates the combination of several advanced capabilities for practical mass spectrometry including high throughput experiments on unmodified samples with unconstrained sample acquisition and fully automated instrumental control and data manipulation. These capabilities are demonstrated with several model mixtures spotted on a PTFE-coated substrate, where the total analysis time was 64 s. Details of the system and discussion of the system performance are provided.

Metabolic study of new psychoactive substance methoxpropamine in mice by UHPLC-QTOF-HRMS.

Methoxpropamine (MXPr) is an arylcyclohexylamine dissociative drug structurally similar to 3-methoxyeticyclidine, ketamine, and deschloroketamine, recently appeared in the European illegal market, and was classified within the new psychoactive substances (NPS). Our study investigated the metabolism of MXPr to elucidate the distribution of the parent drug and its metabolites in body fluids and fur of 16 mice. After the intraperitoneal administration of MXPr (1, 3, and 10mg/kg), urine samples from eight male and eight female mice were collected every hour for six consecutive hours and then at 12- to 24-h intervals. Additionally, plasma samples were collected 24 h after MXPr (1 and 3mg/kg) administration. Urine and plasma were diluted 1:3 with acetonitrile/methanol (95:5) and directly injected into the UHPLC-QTOF-HRMS system. The phase-I and phase-II metabolites were preliminarily identified by means of the fragmentation patterns and the exact masses of both their precursor and fragment ions. Lastly, the mice fur was analyzed following an extraction procedure specific for the keratin matrix. Desmethyl-MXPr-glucoronide was identified in urine as the main metabolite, detected up to 24 h after administration. The presence of norMXPr in urine, plasma, and fur was also relevant, following a N-dealkylation process of the parent drug. Other metabolites that were identified in fur and plasma included desmethyl-MXPr and dihydro-MXPr. Knowledge of the MXPr metabolites evolution is likely to support their introduction as target compounds in NPS toxicological screening analysis on real samples, both to confirm intake and extend the detection window of the dissociative drug MXPr in the biological matrices.

Discovery of a biomarker for β-Thalassemia by HPLC-MS and improvement from Proton Transfer Reaction – Parallel Ion Parking

β-thalassemia is a quantitative hemoglobin (Hb) disorder resulting in reduced production of Hb A and increased levels of Hb A2. Diagnosis of β-thalassemia can be problematic when combined with other structural Hb variants, so that the separation approaches in routine clinical centers are not sufficiently decisive to obtain accurate results. Here, we separate the intact Hb subunits by high-performance liquid chromatography, followed by top-down tandem mass spectrometry of intact subunits to distinguish Hb variants. Proton transfer reaction-parallel ion parking (PTR-PIP), in which a radical anion removes protons from multiply charged precursor ions and produces charge-reduced ions spanning a limited m/z range, was used to increase the signal-to-noise ratio of the subunits of interest. We demonstrate that the δ/β ratio can act as a biomarker to identify β-thalassemia in normal electrospray ionization MS1 and PTR-PIP MS1. The application of PTR-PIP significantly increases the sensitivity and specificity of the HPLC-MS method to identify δ/β ratio as a thalassemia biomarker.

Identifications of Surfactin-Type Biosurfactants Produced by Bacillus Species Isolated from Rhizosphere of Vegetables.

Surfactins are cyclic lipopeptides consisting of a β-hydroxy fatty acid of variable chain length and a peptide ring of seven amino acids linked together by a lactone bridge, forming the cyclic structure of the peptide chain. These compounds are produced mainly by Bacillus species and are well regarded for their antibacterial, antifungal, and antiviral activities. For their surfactin production profiling, several Bacillus strains isolated from vegetable rhizospheres were identified by their fatty acid methyl ester profiles and were tested against phytopathogen bacteria and fungi. The isolates showed significant inhibition against of E. amylovora, X. campestris, B. cinerea, and F. culmorum and caused moderate effects on P. syringae, E. carotovora, A. tumefaciens, F. graminearum, F. solani, and C. gloeosporioides. Then, an HPLC-HESI-MS/MS method was applied to simultaneously carry out the quantitative and in-depth qualitative characterisations on the extracted ferment broths. More than half of the examined Bacillus strains produced surfactin, and the MS/MS spectra analyses of their sodiated precursor ions revealed a total of 29 surfactin variants and homologues, some of them with an extremely large number of peaks with different retention times, suggesting a large number of variations in the branching of their fatty acid chains.

Retention Time Alignment for Protein Turnover Studies Using Heavy Water Metabolic Labeling.

Retention time (RT) alignment has been important for robust protein identification and quantification in proteomics. In data-dependent acquisition mode, whereby the precursor ions are semistochastically chosen for fragmentation in MS/MS, the alignment is used in an approach termed matched between runs (MBR). MBR transfers peptides, which were fragmented and identified in one experiment, to a replicate experiment where they were not identified. Before the MBR transfer, the RTs of experiments are aligned to reduce the chance of erroneous transfers. Despite its widespread use in other areas of quantitative proteomics, RT alignment has not been applied in data analyses for protein turnover using an atom-based stable isotope-labeling agent such as metabolic labeling with deuterium oxide, D2O. Deuterium incorporation changes isotope profiles of intact peptides in full scans and their fragment ions in tandem mass spectra. It reduces the peptide identification rates in current database search engines. Therefore, the MBR becomes more important. Here, we report on an approach to incorporate RT alignment with peptide quantification in studies of proteome turnover using heavy water metabolic labeling and LC-MS. The RT alignment uses correlation-optimized time warping. The alignment, followed by the MBR, improves labeling time point coverage, especially for long labeling durations.

Gas chromatography coupled to time-of-flight mass spectrometry using parallel electron and chemical ionization with permeation tube facilitated reagent ion control for material emission analysis.

Volatile organic compounds (VOCs) emitted by an artificial leather part for car interiors are determined using GC-MS (gas chromatograph coupled to a mass spectrometer) using simultaneous electron and chemical ionization (EI&CI). A device for swift reagent ion switching in CI mode between consecutive runs is presented. VOCs emitted from the investigated material were sampled onto Tenax® absorption tubes using micro emission chambers and subsequently injected into the GC through thermal desorption. The detector was a time-of-flight mass spectrometer (TOFMS) simultaneously operating in EI and CI modes during a single chromatographic run. A custom permeation tube setup allowed for swift selection between various reagent ions in CI mode, e.g., [N2 H]+ , [H3 O]+ , [(H2 O)2 H]+ , and [NH4 ]+ . Different reagent ions are swiftly selectable between single GC runs without hardware changes. Differences in precursor ion survival yields and the selectivity of the various reactants were carefully assessed. Several examples for the improved identification of unknown compounds with the available complementary and comprehensive EI&CI data set are demonstrated for a relevant material emission application. The presented technique provides additional value to the standard GC-EI/MS procedure commonly used for material emission characterization. It allows for a non-targeted analysis approach with moderate analysis time.

A Validated UHPLC–MS/MS Method to Quantify Eight Antibiotics in Quantitative Dried Blood Spots in Support of Pharmacokinetic Studies in Neonates

Conduction of pharmacokinetic (PK) study in pediatric patients is challenging due to blood sampling limits. The dried blood spots (DBS) method represents a potential matrix for microsampling in support of PK studies in children. Herein, we used the Capitainer® qDBS device to develop a DBS method that can collect an exact 10 µL volume of blood on a paper card. This DBS method was developed to simultaneously quantify the concentrations of eight antibiotics, including sulbactam, tazobactam, ampicillin, meropenem, cefotaxime, cefoperazone, piperacillin, and metronidazole using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The prepared DBS samples were extracted in methanol containing acetaminophen as the internal standard at 20 °C on a block bath shaker at 500 rpm for 30 min. The extracted antibiotics were eluted on an Acquity UPLC HSS T3 column (2.1 × 50 mm, 1.8 µm) using gradient elution with a total chromatographic run time of 6.5 min. The precursor and product ions of the analytes were detected by use of the multiple reaction monitoring (MRM) mode. No interfering peaks at the respective retention times of the analytes were observed in DBS samples. The lower limits of quantification (LLOQ) for the antibiotics were between 0.25 and 2.0 μg/mL, and satisfactory accuracies (intra/inter-assay bias -16.7 to +13.6%) and precisions (intra/inter-assay coefficient of variations 1.5-15.6%) were obtained for the analytes. As a proof of concept, the method was applied to DBS samples obtained from neonatal patients treated with ampicillin and piperacillin/sulbactam. The DBS method is simple and robust, and it can be used in children with limited blood sampling.

Comprehensive Identification of Ginsenosides in the Roots and Rhizomes of Panax ginseng Based on Their Molecular Features-Oriented Precursor Ions Selection and Targeted MS/MS Analysis.

Panax ginseng is widely used in Asian countries and its active constituents-ginsenosides-need to be systematically studied. However, only a small part of ginsenosides have been characterized in the roots and rhizomes of panax ginseng (RRPG) up to date, mainly because of a lack of the fragmentation ions of many more ginsenosides. In order to comprehensively identify ginsenosides in RRPG, molecular features of ginsenosides orienting precursor ions selection and targeted tandem mass spectrometry (MS/MS) analysis strategy were proposed in our study, in which the precursor ions were selected according to the molecular features of ginsenosides irrespective of their peak abundances, and targeted MS/MS analysis was then performed to obtain their fragmentation ions for substance characterization. Using this strategy, a total of 620 ginsenosides were successfully characterized in RRPG, including 309 protopanaxadiol-type ginsenosides, 258 protopanaxatriol-type ginsenosides and 53 oleanane-type ginsenosides. It is worth noting that, except for the known aglycones mass-to-charge ratio (m/z) 459, 475 and 455, twelve other aglycones, including m/z 509, 507, 493, 491, 489, 487, 477, 473, 461, 457, 443 and 441, were first reported in our experiment and they were probably the derivatizations of the protopanaxatriol and protopanaxadiol. Our study will not only help people to improve the cognition of ginsenosides in RRPG, but will also play a guiding and reference role for the isolation and characterization of potentially new ginsenosides from RRPG.

A Simple and Sensitive LC-MS/MS for Quantitation of ICG in Rat Plasma: Application to a Pre-Clinical Pharmacokinetic Study

A selective, sensitive, and rapid liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantitation of ICG in rat plasma. The chromatographic separation was achieved using an ACE excel C18 (3 µm, 50 × 3.0 mm) column, with a mobile phase composition of 0.1% formic acid and 0.1% formic acid in acetonitrile, using a gradient flow at a rate of 0.3 mL/min. The MS was operated at a unit resolution in the multiple reaction monitoring mode, using the precursor ion → product ion combinations of 753.3 → 330.2 m/z (ICG) and 747.45 → 717.50 (Cy7.5 amine) with a run time of 5 min. The assay was linear over a concentration range of 1–1000 ng/mL with a regression coefficient (r2) of 0.998 or better. The inter and intra-batch precision (% relative standard deviation, %RSD) was lower than 13.5%, with accuracy (%Bias) between −10.03% and 11.56%. The ICG was stable under laboratory storage and handling conditions. The validated method was successfully applied to preclinical pharmacokinetic (PK) studies of ICG at a dose of 0.39 mg/kg in rats. PK parameters suggested the highest plasma concentration within 2 min of intravenous dosing with restricted systemic distribution and rapid clearance.

Two-dimensional code enables visibly mapping herbal medicine chemome: an application in Ganoderma lucidum

BackgroundChemical profile provides the pronounced evidence for herbal medicine (HM) authentication; however, the chemome is extremely sophisticated. Fortunately, two-dimensional (2D) code, as a quick response means, is conceptually able to store abundant information, exactly fulfilling the chemical information storage demands of HMs.MethodsWe here attempted to denote both MS^1 and MS^2 dataset of HM with a single 2D-code chart. Measurement of Ganoderma lucidum that is one of the most famous HMs with LC–MS/MS was employed to illustrate the “coding-decoding” workflow for the conversion amongst MS/MS dataset, 2D-code, and chemical profile, and to evaluate the applicability as well. After data acquisition, and m/z value of each deprotonated molecular signal was divided into integer and decimal portions, corresponding to x and y coordinates of 2D-plot, respectively. On the other side, m/z values of all its fragment ions were exactly assigned to serial x values sharing an identical y value being equal to the precursor ion. 2D-code was thereafter produced by plotting these defined dots at a 2D-chart. Regarding a given 2D-code map, the entire chart (x coordinate: 0–600; y coordinate: 0–600) was fragmented into two regions by the line of y=x. MS^1 spectral signals always located below the line, whereas all fragment ions lay at the left zone. After extracting information from the edges of each square frame, m/z values of both precursor ion and fragment ions could be harvested and putatively deciphered to a compound through applying some empirical mass fragmentation rules.ResultsThe entire code of Ganoderma lucidum fruit bodies therefore corresponded exactly to a compound set. The elution program, even the employment of direct infusion, couldn’t significantly impact the code, and dramatical differences occurred between different species and amongst different parts of Ganoderma lucidum as well. Not only ganoderic acid cluster but also certain primary metabolites served as the diagnostic compounds towards species differentiation.Conclusion2D-code might be a meaningful, practical visual way for rapid HM recognition because it is convenient to achieve the conversion amongst MS/MS dataset, 2D-barcode plot, and the chemome.

Selective Schiff base formation via gas-phase ion/ion reactions to enable differentiation of isobaric lipids in imaging mass spectrometry.

The separation and identification of lipids in complex mixtures are critical to deciphering their cellular functions. Failure to resolve isobaric compounds (e.g., via high mass resolution or tandem mass spectrometry) can result in incorrect identifications in mass spectrometry experiments. In imaging mass spectrometry, unresolved peaks can also result in composite images of multiple compounds, giving inaccurate depictions of molecular distributions. Gas-phase ion/ion reactions can be used to selectively react with specific chemical functional groups on a target analyte, thereby extracting it from a complex mixture and shifting its m/z value to an unobstructed region of the mass range. Herein, we use selective Schiff base formation via a novel charge inversion ion/ion reaction to purify phosphatidylserines from other isobaric (i.e., same nominal mass) lipids and reveal their singular distributions in imaging mass spectrometry. The selective Schiff base formation between singly deprotonated phosphatidylserine (PS) lipid anions and doubly charged N,N,N',N'-tetramethyl-N,N'-bis(6-oxohexyl)hexane-1,6-diaminium (TMODA) cations is performed using a modified commercial dual source hybrid Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. This process is demonstrated using the isobaric lipids [PS 40:6 - H]- (m/z 834.528) and [SHexCer d38:1 - H]- (m/z 834.576), which produces [PS 40:6 + TMODA - H - H2O]+ (m/z 1186.879), and [SHexCer d38:1 + TMODA-H]+ (m/z 1204.938) product ions following the gas-phase charge inversion reaction. These product ions differ by roughly 18Da in mass and are easily separated by low mass resolution analysis, while the isobaric precursor ions require roughly 45,000 mass resolving power (full-width at half maximum) to separate. Imaging mass spectrometry using targeted gas-phase ion/ion reactions shows distinct spatial distributions for the separated lipid product ions relative to the composite images of the unseparated precursor ions.

Development of a Machine Learning Algorithm for Drug Screening Analysis on High-Resolution UPLC-MSE/QTOF Mass Spectrometry.

Ultra-performance liquid chromatography (UPLC)-MSE/quadrupole time-of-flight (QTOF) high-resolution mass spectrometry employs untargeted, data-independent acquisition in a dual mode that simultaneously collects precursor ions and product ions at low and ramped collision energies, respectively. However, algorithmic analysis of large-scale multivariate data of comprehensive drug screening as well as the positivity criteria of drug identification have not been systematically investigated. It is also unclear whether ion ratio (IR), the intensity ratio of a defined product ion divided by the precursor ion, is a stable parameter that can be incorporated into the MSE/QTOF data analysis algorithm. IR of 91 drugs were experimentally determined and variation of IR was investigated across 5 concentrations measured on 3 different days. A data-driven machine learning approach was employed to develop multivariate linear regression (MLR) models incorporating mass error, retention time, number of detected fragment ions and IR, accuracy of isotope abundance, and peak response using drug-supplemented urine samples. Performance of the models was evaluated in an independent data set of unknown clinical urine samples in comparison with the results of manual analysis. IR of most compounds acquired by MSE/QTOF were low and concentration-dependent (i.e., IR increased at higher concentrations). We developed an MLR model with composite score outputs incorporating 7 parameters to predict positive drug identification. The model achieved a mean accuracy of 89.38% in the validation set and 87.92% agreement in the test set. The MLR model incorporating all contributing parameters can serve as a decision-support tool to facilitate objective drug identification using UPLC-MSE/QTOF.

PICA: Pixel Intensity Correlation Analysis for Deconvolution and Metabolite Identification in Mass Spectrometry Imaging

In-source fragmentation (ISF) is a naturally occurring phenomenon in various ion sources including soft ionization techniques such as matrix-assisted laser desorption/ionization (MALDI). It has traditionally been minimized as it makes the dataset more complex and often leads to mis-annotation of metabolites. Here, we introduce an approach termed PICA (for pixel intensity correlation analysis) that takes advantage of ISF in MALDI imaging to increase confidence in metabolite identification. In PICA, the extraction and association of in-source fragments to their precursor ion results in "pseudo-MS/MS spectra" that can be used for identification. We examined PICA using three different datasets, two of which were published previously and included validated metabolites annotation. We show that highly colocalized ions possessing Pearson correlation coefficient (PCC) ≥ 0.9 for a given precursor ion are mainly its in-source fragments, natural isotopes, adduct ions, or multimers. These ions provide rich information for their precursor ion identification. In addition, our results show that moderately colocalized ions (PCC < 0.9) may be structurally related to the precursor ion, which allows for the identification of unknown metabolites through known ones. Finally, we propose three strategies to reduce the total computation time for PICA in MALDI imaging. To conclude, PICA provides an efficient approach to extract and group ions stemming from the same metabolites in MALDI imaging and thus allows for high-confidence metabolite identification.

Suspect Screening and Semi-Quantification of Macrolide Antibiotics in Municipal Wastewater by High-Performance Liquid Chromatography—Precursor Ion Scan Tandem Mass Spectrometry

Macrolides are widely used in medicine and veterinary medicine, and are the leading antibiotics in terms of consumption. The release of macrolides and their metabolites into the environment through municipal wastewater can have an adverse effect on aquatic ecosystems and human health. In the present study, a method for the non-targeted screening and semi-quantitative determination of macrolide antibiotics and their derivatives in wastewater based on a combination of chromatographic separation and tandem mass spectrometric detection in precursor ion scan (PrecIS) mode has been proposed. Product ions with m/z 158 and 174 related to specific desosamine fragments were used as diagnostic ions for the PrecIS detection of the macrolide structures without (14- and 15-membered macrocycles) and with a (16-membered macrocycle) glycosylated desosamine moiety, respectively. The combination of the optimized solid phase extraction procedure and HPLC-MS/MS analysis in PrecIS mode allowed for the suspect screening of macrolides in municipal wastewater with limits of detection in the range of 4–150 ng L−1. The developed approach made it possible to detect and tentatively identify in municipal wastewater 17 compounds belonging to the macrolide class, including azithromycin, clarithromycin, josamycin and 14 metabolites with a total concentration of 1450 ng L−1.

Automation of liquid crystal phase analysis for SAXS, including the rapid production of novel phase diagrams for SDS-water-PIL systems.

Lyotropic liquid crystal phases (LCPs) are widely studied for diverse applications, including protein crystallization and drug delivery. The structure and properties of LCPs vary widely depending on the composition, concentration, temperature, pH, and pressure. High-throughput structural characterization approaches, such as small-angle x-ray scattering (SAXS), are important to cover meaningfully large compositional spaces. However, high-throughput LCP phase analysis for SAXS data is currently lacking, particularly for patterns of multiphase mixtures. In this paper, we develop semi-automated software for high throughput LCP phase identification from SAXS data. We validate the accuracy and time-savings of this software on a total of 668 SAXS patterns for the LCPs of the amphiphile hexadecyltrimethylammonium bromide (CTAB) in 53 acidic or basic ionic liquid derived solvents, within a temperature range of 25-75 °C. The solvents were derived from stoichiometric ethylammonium nitrate (EAN) or ethanolammonium nitrate (EtAN) by adding water to vary the ionicity, and adding precursor ions of ethylamine, ethanolamine, and nitric acid to vary the pH. The thermal stability ranges and lattice parameters for CTAB-based LCPs obtained from the semi-automated analysis showed equivalent accuracy to manual analysis, the results of which were previously published. A time comparison of 40 CTAB systems demonstrated that the automated phase identification procedure was more than 20 times faster than manual analysis. Moreover, the high throughput identification procedure was also applied to 300 unpublished scattering patterns of sodium dodecyl-sulfate in the same EAN and EtAN based solvents in this study, to construct phase diagrams that exhibit phase transitions from micellar, to hexagonal, cubic, and lamellar LCPs. The accuracy and significantly low analysis time of the high throughput identification procedure validates a new, rapid, unrestricted analytical method for the determination of LCPs.

Perspectives and opinions from scientific leaders on the evolution of data-independent acquisition for quantitative proteomics and novel biological applications

The methodology of data-independent acquisition (DIA) within mass spectrometry (MS) was developed into a method of choice for quantitative proteomics, to capture the depth and dynamics of biological systems, and to perform large-scale protein quantification. DIA provides deep quantitative proteome coverage with high sensitivity, high quantitative accuracy, and excellent acquisition-to-acquisition reproducibility. DIA workflows benefited from the latest advancements in MS instrumentation, acquisition/isolation schemes, and computational algorithms, which have further improved data quality and sample throughput. This powerful DIA-MS scan type selects all precursor ions contained in pre-determined isolation windows, and systematically fragments all precursor ions from each window by tandem mass spectrometry, subsequently covering the entire precursor ion m/z range. Comprehensive proteolytic peptide identification and label-free quantification are achieved post-acquisition using spectral library-based or library-free approaches. To celebrate the &gt; 10 years of success of this quantitative DIA workflow, we interviewed some of the scientific leaders who have provided crucial improvements to DIA, to the quantification accuracy and proteome depth achieved, and who have explored DIA applications across a wide range of biology. We discuss acquisition strategies that improve specificity using different isolation schemes, and that reduce complexity by combining DIA with sophisticated chromatography or ion mobility separation. Significant leaps forward were achieved by evolving data processing strategies, such as library-free processing, and machine learning to interrogate data more deeply. Finally, we highlight some of the diverse biological applications that use DIA-MS methods, including large-scale quantitative proteomics, post-translational modification studies, single-cell analysis, food science, forensics, and small molecule analysis.

Monitoring of n-hexane degradation in a plasma reactor by chemical ionization mass spectrometry.

n-Hexane (C6H14) removal and conversion are investigated in a filamentary plasma generated by a pulsed high-voltage Dielectric Barrier Discharge (DBD) at atmospheric pressure and room temperature in a dry N2/O2 (20%) mixture with C6H14. The degradation of n-hexane and the by-product formation are analyzed in real-time using a high-resolution Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometer coupled with Chemical Ionization (CI). As alkanes are reacting slowly with H3O+ ions, two precursor ions were used: O2+ to follow the n-hexane mixing ratios and H3O+ to follow the mixing ratios of organic by-products. As the CI-FTICR technique can work at high mixing ratios, studies were made between 5 and 200 ppm of n-hexane. Absorption spectroscopy is also used to follow ozone and carbon dioxide molecules. We show that the DBD efficiency increases for lower n-hexane mixing ratios and a large number of by-products are identified, with the major compounds being: formaldehyde, acetaldehyde, propanal, carbon dioxide, and carbon monoxide along with nitrate compounds. Based on the nature of the by-products characterized, a mechanism accounting for their formation is proposed.