RATIONALE: Sample preparation is one of the most crucial steps for MALDI mass spectrometry imaging (MALDI-MSI). The scientists beginning their adventure with this technique may be overwhelmed by the variety of matrices, solvents, concentrations, the ways of their applications, and the lack of widely available knowledge about the influence of these parameters on the results. Here we would like to present our experiences with detailed aspects of matrices deposition, hopefully helpful for the scientific community. METHODS: In our article, we have tested several MALDI matrices applied by the SunCollect® system: wet-interface matrix deposition in the context of lipids analysis. Among them: 2,5-dihydroxybenzoic acid (DHB), norharmane, N-(1-naphthyl) ethylenediamine dihydrochloride (NEDC), 9-aminoacridine (9AA). We have optimized the number of matrix layers and nozzle settings in terms of spectra intensity and the overall quality of obtained ion maps. RESULTS: Our research presents the influence of the number of matrix layers and nozzle settings on the results and allows for choosing the optimal parameters for the analyses. In positive ionization mode, DHB matrix could be chosen as the first selection. In the negative ionization mode, DAN matrix produces higher peak intensity in a lower mass range and seems to provide more information than 9AA. We recommended NEDC for particular tasks such as glucose analysis. Comparably to remaining matrices, norharmane significantly changes received ion maps. CONCLUSIONS: Dealing with such a great amount of data allows us to notice an interesting conclusion: the obtained ion picture for a particular ion could differ dramatically with changing the matrix, the solvent composition, or even the number of matrix layers. This must be considered when interpreting the result and forces us to compare the results obtained with different matrices with extreme caution.

A document by Simone Moretti. Click on the document to view its contents.

The traditional van Krevelen diagram, the nominal oxidation of organic carbon, and several aromaticity indexes generally considered C, H, O, N, P, and S factors, or just C, H, and O. However, these evaluated methods may provide incorrect interpretation for high-resolution mass data of organics containing halogen elements. Therefore, we adapted the van Krevelen diagram and the other indexes with halogen elements and verified with 2235 model organics. The results demonstrated that the modified van Krevelen diagram and the adjusted indexes were more accurate for the analysis of mass data, either in the compound classification or in the evaluation of oxidation state of organic matter.

Rationale: Trimetazidine and its metabolites are prohibited substances in sports. With a growing number of adverse findings in human athletes, it is crucial to develop doping control strategies that include screening for trimetazidine in animal sports. This study aims to detect and characterize trimetazidine and its metabolites for doping control in camel racing. Methods: Camel urine and plasma samples were collected from four healthy animals following a single oral dose of trimetazidine. invitro studies utilized camel liver cells. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) techniques were employed for the extraction of trimetazidine metabolites from plasma and urine matrices, the metabolites were analyzed using a thermo Orbitrap exploris LCMS system with optimized settings to achieve maximum sensitivity and accurate mass measurements. Results: Comprehensive metabolite profiling of trimetazidine in camels revealed the identification of seven phase I and five phase II metabolites. Phase I metabolites were primarily formed through delakylation, while phase II metabolites were dominated by glucuronide conjugation of demethylated trimetazidine. The findings provided insights into the distinct metabolic pathways and biotransformation patterns of trimetazidine in camels under the experimental conditions. Conclusion: The developed method enables detection and characterization of trimetazidine and its metabolites in camels. The identified metabolites have the potential to serve as biomarkers for trimetazidine abuse in camel racing .this study provides valuable insights into the metabolism of trimetazidine in camels.

A document by Colette LaMonica Kelly. Click on the document to view its contents.

Rationale Na v1.1, 1.2 and 1.6 are transmembrane proteins acting as voltage gated sodium channels implicated in various forms of epilepsy. There is a need for knowing their actual concentration in target tissues during drug development. Methods Unique peptides for Na v1.1, Na v1.2 and Na v1.6 were selected as quantotropic peptides for each protein and used for their quantification in plasma membranes from stably transfected HEK293 cells and rodent and human brain samples using ultra‐high‐performance liquid chromatography/electrospray ionization tandem mass spectrometry. Results Na v 1.1, 1.2 and 1.6 protein expressions in three stably individually transfected HEK293 cell lines were found to be 2.1±0.2, 6.4±1.2 and 4.0±0.6 fmole/µg membrane protein respectively. Na v1.2 showed the highest expression, with approximately 3 times higher (p<0.003) in rodents than in human at 3.05±0.57, 3.35±0.56 in mouse and rat brains and 1.09±0.27 fmole/µg in human, respectively. Both Na v1.1 and 1.6 expressions were much lower than Na v1.2, with approximately 40% less expression in human Na v1.1 when compared with rodents Na v1.1 at 0.49±0.1 (mouse), 0.43±0.3 (rat), and 0.28±0.04 (human); while Na v1.6 was approximately 60% less expression in human when compared to rodents at 0.27±0.09 (mouse), 0.26±0.06 (rat) and 0.11±0.02 (human) fmole/µg membrane proteins. Conclusions MRM was used to quantify sodium channels Na v1.1, 1.2 and 1.6 expressed in stably transfected HEK293 cells and brain tissues from mouse, rat, and human. We found significant differences in the expression of these channels in mouse, rat, and human brains. Na v expression ranking among the three species was Na v1.2 >> Na v1.1> Na v1.6, with the human brain expressing much lower concentrations overall in comparison to rodents.

Rationale. Femtoamp and picoamp electrospray ionization characteristics of a non-polar solvent were explored. The direct ESI-MS analysis of chloroform extract solution enabled rapid analysis of perfluorinated sulfonic acid (PFS) analytes in drinking water. Methods. Neat chloroform solvent and extracts were directly used in a typical wire-in ESI setup using micrometer emitter tips. Ionization currents were measured with femtoamp sensitivity while ramping the spray voltage from 0 to -5000 V. Methanol was used to illustrate the characteristics of spraying chloroform. The effect of spray voltage and inlet temperature was studied. A liquid-liquid extraction workflow was developed to analyze PFOS in drinking water using an ion trap mass spectrometer. Results. The ionization onset of chloroform solution was 41 ± 17 fA at 300 V. The ionization current gradually increased with voltage while remaining below 100 pA when using voltage up to -5000 V. PFOS ion signal was significantly enhanced to improve the detection limit to 25 ppt in chloroform. Coupled with a liquid-liquid extraction workflow, detection limits of 0.38-5.1 ppt, and a quantitation range of 5-400 ppt were achieved for perfluorinated sulfonic compounds in 1 mL drinking water samples. Conclusions. Femtoamp and picoamp modes expand the solvent compatibility range of electrospray ionization and can enable quantitative analysis in ppt concentrations.

RATIONALE Ambient ionization mass spectrometry (AIMS) delivers realistic data from samples in their native state. In addition, AIMS methods reduce time and costs for sample preparation and have less environmental impact. However, AIMS data are often complex and require substantial processing before interpretation. METHODS We developed an interactive R script for the guided processing of mass spectrometry (MS) data. The ‘MQ_Assistant’ is based on MALDIquant, a popular R package for MS data processing. In each step, the user can try and pre-view the effect of chosen parameters before deciding on the values with the best result and proceeding to the next stage. The outcome of the MQ_Assistant is a feature matrix that can be further analyzed in R and statistics tools such as MetaboAnalyst. RESULTS Using 360 AIMS example spectra, we demonstrate the step-by-step processing for creating a feature matrix. In addition, we show how to visualize the results of tree biological replicates of a plant-microbe interaction between Arabidopsis and Trichoderma as a heatmap using R and upload them to MetaboAnalyst. The final parameter set can be saved for reuse in MALDIquant workflows of similar data. CONCLUSIONS The MQ_Assistant helps novices and experienced users to develop workflows for (AI)MS data processing. The interactive procedure supports the quick finding of appropriate settings. These parameters can be exported and reused in future projects. The step-wise operation with visual feedback also suggests the use of the MQ_Assistant in education.

Rational: Organisms that grow a hard carbonate shell or skeleton, such as foraminifera, corals or molluscs, incorporate trace elements into their shell during growth that absorbs the environmental change and biological activity they experienced. These geochemical signals locked within the carbonate are archives used in proxy reconstructions to study past environments and climates, to decipher taxonomy of cryptic species and to resolve evolutionary responses to climatic changes. Methods: Here we use a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a time resolved acquisition to quantify the elemental composition of carbonate shells. We present the LABLASTER (Laser Ablation BLASt Through Endpoint in R) package, which imports a single time resolved LA-ICP-MS analysis, then detects when the laser has ablated through the carbonate as a function of change in signal over time, and outputs key summary statistics. We provide two worked examples within the package: a planktic foraminifera and a tropical coral. Results: We present the first R package that improves signal: noise ratios in data reduction workflows by automating the detection of when the laser has ablated through a sample using a smoothed time-series and subsequent removal of off-target data points. The functions are flexible and adjust dynamically to enhance the signal: noise ratio of the desired geochemical target. Visualisation tools for manual validation are also included. Conclusions: LABLASTER increases transparency and repeatability by algorithmically identifying when the laser has either ablated fully through a sample or across a mineral boundary and is thus no longer documenting a geochemical signal associated with the desired sample. LABLASTER’s focus on better data targeting means more accurate extraction of biological and geochemical signals.

RATIONALE Boron isotopes are a powerful tool for pH reconstruction in marine carbonates and as tracer for fluid-mineral interaction in geochemistry. Micro-analytical approaches based on laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) often suffer from effects induced by the sample matrix. In this study, we investigated matrix-independent analyses of B isotopic ratios and applied this technique to cold-water corals. METHODS We employed a customized 193 nm femtosecond laser ablation system (Solstice, Spectra-Physics) coupled to a MC-ICP-MS (Nu Plasma II, Nu Instruments) equipped with electron multipliers for in situ measurements of B isotope ratios (11B/10B) at the micron-scale. We analyzed various reference materials of silicate and carbonate matrices using non-matrix match calibration without employing any correction mode. This approach was then applied to investigates defined increments in coral samples from a Chilean fjord. RESULTS We obtained accurate B isotope ratios with a precision of ± 0.9‰ (2 SD) for various reference materials including silicate glasses (GOR132-G, StHs6/80-G, ATHO-G, and NIST SRM 612), clay (IAEA-B-8) and carbonate (JCp-1) using the silicate glass NIST SRM 610 as calibration standard, which shows that neither laser-induced nor ICP-related matrix effects are detectable. The application to cold-water corals (Desmophyllum dianthus) reveal little intra-skeleton variations in δ11B with average values between 23.27 and 26.09‰. CONCLUSIONS Our instrumental set-up provides accurate and precise B isotopic ratios independently of the sample matrix at the micron-scale. This approach opens a wide field of application in geochemistry, including pH reconstruction in biogenic carbonates and deciphering processes related to fluid-mineral interaction.

RATIONALE: SLAP is one of the two calibration materials for the isotopic water scale. By consensus the established δ 18O value is -55.5‰, although there are firm indications that δ 18O SLAP is significantly more negative. The real δ 18O SLAP value as such does not influence the isotopic water scale, however knowledge of the size of isotopic scale contraction in stable isotope measurements is vital for second order isotopes. In this study quantification of δ 18O SLAP with respect to δ 18O VSMOW is described. METHODS: SLAP-like water was quantitatively mixed with highly 18O enriched water to mimic VSMOW. The 18O concentration was determined using an electron ionization quadrupole mass spectrometer. The isotopic composition of the SLAP-like and VSMOW-like waters were measured with an optical spectrometer, alongside real VSMOW and SLAP. RESULTS: This study resulted in a much more depleted δ 18O value for SLAP than expected. The averaged outcome of 7 independent experiments is δ 18O SLAP -56.33 ± 0.03‰. There is a large discrepancy between the actual isotopic measurements of even the most carefully operating groups and the true δ 18O value. CONCLUSIONS: Although this finding as such does not influence the use of the VSMOW-SLAP scale, it raises the intriguing question what we actually measure with our instruments, and why even a fully corrected measurement can be so far off. Our result has consequences for issues like the transfer of δ 18O from and to the VPDB scale, various fractionation factors, and the Δ 17O. The absolute 18O abundance for SLAP was determined at 1.88798 (43) x 10 -3 based on the absolute 18O abundance of VSMOW and the presented δ 18O SLAP in this paper.

Within the framework of radioactive waste management, the evolution of the gaseous composition inside the underground repository structures must be understood. Indeed, chemical and microbial reactions and exchanges occur between the rock, the structures and the air. These processes are studied in the Andra’s Meuse/Haute-Marne Underground Research Laboratory’s (URL). Recently, a gas monitoring station “Flair soil™” has been designed to monitor the gaseous composition inside this URL. This station is composed by two analyzers: a quadrupole mass spectrometer (QMS) which allows to follow the evolution of several gases and an infrared laser spectroscope (Picarro) providing simultaneous measurements of CH4, CO2 and CO. Thus, a multivariate calibration method for the quantitative detection of interfering and non-interfering gases in a nitrogen matrix has been developed for the QMS. The MS was calibrated from pure gases in a nitrogen matrix, with known concentrations and ion currents obtained from the measurement of each species of gas. This method uses matrix calculations to calculate the relative concentrations of an unknown gas mixture from the ion currents measured directly in the MS. The test gases T1 and T2 were used to assess the accuracy of the method. Daily ion currents are corrected from theoretical ion currents obtained from calibration coefficients and test gas concentrations. Some gases are less well quantified due to their low concentration in the test gases and interferences on the measured masses. One of the motivations of this study lay in developing an advanced measurement tool allowing to be low in sensitivity, and thus to improve the detection and quantification of gases at low concentrations. The objective of this paper is to propose an analytical method to measure the gaseous composition with several molecules. This method was able to detect hydrocarbons, noble gases, sulfides, greenhouse gases, oxygen, hydrogen, nitrogen in the same mixture.

Rationale: Many insect species undertake multi-generational migrations in the Afro-tropical and Palearctic ranges, and understanding their migratory connectivity remains challenging due to their small size, short life span and large population sizes. Hydrogen isotope ( δ 2H) can be used to reconstruct the movement of dispersing or migrating insects, but applying δ 2H for provenance requires a robust isotope baseline map (i.e., isoscape) for the Afro-Palearctic. Methods: We analysed the δ 2H in the wings ( δ 2H wing) of 142 resident butterflies from 56 sites across the Afro-Palearctic. The δ 2H wing values were compared to the predicted local growing-season precipitation δ 2H values ( δ 2H GSP) using a linear regression model to develop an insect wing δ 2H isoscape. We used multivariate linear mixed models and high-resolution and time-specific remote sensing climate and environmental data to explore the controls of the residual δ 2H wing variability. Results: A strong linear relationship was found between δ 2H wing and δ 2H GSP values (r 2=0.53). The resulting isoscape showed strong patterns across the Palearctic but limited variation and high uncertainty for the Afro-tropics. Positive residuals of this relationship were correlated with dry conditions for the month preceding sampling whereas negative residuals were correlated with more wet days for the month preceding sampling. High intra-site δ 2H wing variance was associated with lower relative humidity for the month preceding sampling and higher elevation. Conclusion: The δ 2H wing isoscape is applicable to trace butterflies, moths and other terrestrial herbivorous insects that migrate across the Afro-Palearctic range but has limited geolocation potential in the Afro-tropics. The spatial analysis of uncertainty using high-resolution climatic data demonstrated that many African regions with highly variable evaporation rates and relative humidity have δ 2H wing values that are less related to δ 2H GSP values. Increasing geolocation precision will require new modeling approaches using more time-specific environmental data and/or independent geolocation tools.

A document by Chaohui Qiu. Click on the document to view its contents.

The researcher will introduce the way of effective liquid chromatography tandem mass spectrometric method (HPLC-MS) which is quick, sensitive, and alternative to determine the (E)-3-(3,4-dihydroxyphenyl) -2-(3-(3,4-dihydroxyphenyl)acrylamido)propanoic acid (A1) and rosmarinic acid (RA) of the plasma in rats. The analyses were divided into a C18 column (1.9 μm, 2.1 mm × 100 mm) with a security guard C18 column (5 μm, 2.1 mm × 10 mm) and a triple-quadrupole mass spectrometry with an electrospray ionization (ESI) ion-source generates ions. With Pseudoephedrine hydrochloride being a standard, the sample pretreatment is relevant to the one-step protein precipitation with isopropanol: ethyl acetate (v/v, 20:80). This method presented a linear relationship within ranges of the concentration of 5–750 ng/ml for RA and A1. Relative standard deviations (RSD) in daily courses stood less than 15% and the relative errors (RE) registered within 15%. The means adopted in this research makes the RA’s and A1’s unambiguous quantification and identification and in vivo possible. And this study can be the first one to focus on determining the A1 and RA of rat plasma with administration orally. The results served as a significant basis to evaluate the medicine’s applications in the clinic.

RATIONALE: The thiosuccinimide linker is widely used in the synthesis of bioconjugates. However, it is susceptible to hydrolysis and is transformed into its hydrolyzed and/or the isobaric thiazine forms, the latter of which is a fairly common product in a conjugate that contains a cysteinyl peptide. MALDI-MS and MS/MS are useful for differentiating these isobaric species. METHODS: Four cross-linked peptides with thiosuccinimide linkers were synthesized. Analogs with the linker that were transformed into thiazine and/or the hydrolyzed thiosuccinimide linkers were then generated by incubating the samples at neutral or basic pH. All of the cross-linked peptides were purified by rp-HPLC and differentiated by MALDI-MS, -MS/MS and UVPD. RESULTS: A cysteinyl peptide-containing conjugate, the thiosuccinimide form, was largely transformed into the hydrolyzed or thiazine forms after incubation at neutral or basic pH. MALDI-MS allowed the three forms to be differentiated: the thiosuccinimide and its hydrolysis product gave two constituent peptides after reductive cleavage between the Cys and succinimide moieties; no fragment ions were produced from the thiazine form. In addition, MALDI-MS/MS of the thiosuccinimide form yielded two pairs of complementary fragment ions via 1,4-elimination: Cys-SH and maleimide, and dehydro-alanine and thiosuccinimide, which are different from those produced via reductive cleavage in MALDI-MS. The thiazine form gave fragment ions resulting from the cleavage of the newly formed amide bond in the linker that arose from thiazine formation. CONCLUSIONS: The thiosuccinimide (but not thiazine) form of the cross-linked peptide yielded individual constituent peptides in MALDI-MS; MALDI-MS/MS showing specific 1,4-elimination for the thiosuccinimide form and cleavage at the newly formed peptide bond via transcyclisation for the thiazine form.

Rationale: Position-Specific (PS) δ13C values of propane has proven its ability to provide valuable information on evolution history of natural gases. Two major approaches to measure PS δ13C values of propane are quantitative NMR (qNMR) and GC-Py(rolysis)-GC-IRMS. The qNMR has verified measurement accuracy, however, required large sample size and long experimental time limit its applications. The GC-Py-GC-IRMS is more versatile method with small sample size, but its accuracy has not been demonstrated. Methods: We measured PS δ13C values of propane from nine natural gases, using the both methods and evaluated the accuracy of GC-Py-GC-IRMS method. Results: The results show that large carbon isotope fractionations occurred for the both terminal and central carbons within propane during pyrolysis. The isotope fractionations during the pyrolysis are reproducible at optimum conditions, but vary between the two GC-Py-GC-IRMS systems tested, affected by experimental conditions (e.g., pyrolysis temperature, flow rate, and reactor conditions). Conclusions: Therefore, it is necessary to evaluate and calibrate each GC-Py-GC-IRMS system using propane gases whose PS δ13C values are accurately determined. This study also highlights a need of PS isotope standards for propane and other molecules.

RATIONALE: The high sensitivity of the miniature mass spectrometer plays an irreplaceable role in rapid on-site detection. However, its analysis accuracy and stability should be improved due to the influence of sample pretreatment and use environment. The present study investigates the processing effects of EEMD feature enhancement methods on the determination coefficient and relative standard deviation of caffeine mass spectrometry signals. METHODS: This paper employs the EEMD method combined with polynomial curve fitting to enhance the characteristics of seven Caffeine mass spectrum signals with different concentrations and fifteen groups of Caffeine mass spectrum signals with the same concentration, and the wavelet analysis method was used for comparative verification. The determination coefficient and relative standard deviation of the two methods were compared. RESULTS: We found the EEMD method’s capability in adaptively decomposing Caffeine mass spectrum signals is better than wavelet analysis method. The determination coefficient of the EEMD enhanced feature is better than 0.999, and the relative standard deviation is better than 2%, and both are better than wavelet analysis methods. CONCLUSIONS: The feature enhancement processing using the EEMD method has significantly improved the determination coefficient and relative standard deviation of the sample curve, improving the accuracy and stability of the data and providing a new way for miniature mass spectrometer signal processing.