Pressure Electrospray Ionization Research Articles

Arc-Induced Electrospray Ionization Mass Spectrometry.

Arc-induced electrospray ionization mass spectrometry (AESI-MS) was developed during which alternating current electrospray is simply achieved through the arc plasma. The AESI source exploits the arc's temperature and charge properties to generate aerosols consisting of charged microdroplets. The electrospray region, in which organic molecules are contained within microdroplets, partially overlaps with the arc plasma region. Guided by the electric field, these molecules undergo ionization, yielding ionic target analytes. AESI represents a soft ionization method that combines the mechanisms of atmospheric pressure chemical ionization and electrospray ionization, facilitating the ionization of analytes with wide ranging polarities. The precisely targeted spraying area enhances ion entry into the mass analyzer, thereby enabling excellent ionization efficiency. The AESI source exhibits several notable advantages over the electrospray ionization source, including an elevated but comparable level of active species concentrations and types, simplified mass spectra for direct amino acid analysis, high salt tolerance, versatile analysis of compounds with varying polarities, and reliable quantitative analysis of amino acids in complex matrices. Overall, AESI broadens the methodologies employed to generate microdroplets, providing a technological and scientific framework for creating distinctive electrospray ionization techniques.

Determination, Method Development and Validation of Six Nitrosamine Impurities in Purified water by using LC-MS/MS

N-nitroso dimethylamine (NDMA) and some other N-nitrosamines has been detected as potent mutagenic and carcinogenic arising in purified water due to the use of potable water required for production of purified water. The dominating precursors of N-nitrosamines formation during the purified water disinfection process are secondary and tertiary amines. NDMA is a disinfection of product found by the ozonation and chlorination of purified water. A high-performance liquid chromatography tandem mass spectrometry was developed to study the appearance of N-nitrosamines in purified water. The compounds were detected by Atmospheric Pressure Chemical Ionization (APCI) or Electrospray Ionization (ESI) which are the ionization modes with multiple reaction monitoring mode. Chromatographic separation was performed on a Phenomenex kinetex F5 column having the size 250 × 4.6mm, 5µ. This study proves that NMBA, NDMA, NDEA, NEIPA, NDIPA and NDBA detected in the purified water. Finally, the developed analytical method was strongly applied to the analysis of N-nitrosamines in purified water.

Two Rings Around One Ball: Stability and Charge Localization of [1 : 1] and [2 : 1] Complex Ions of [10]CPP and C60/70 [ *

We investigate the gas-phase chemistry of noncovalent complexes of [10]cycloparaphenylene ([10]CPP) with C60 and C70 by means of atmospheric pressure photoionization and electrospray ionization mass spectrometry. The literature-known [1 : 1] complexes, namely [10]CPP⊃C60 and [10]CPP⊃C70 , are observed as radical cations and anions. Their stability and charge distribution are studied using energy-resolved collision-induced dissociation (ER-CID). These measurements reveal that complexes with a C70 core exhibit a greater stability and, on the other hand, that the radical cations are more stable than the respective radical anions. Regarding the charge distribution, in anionic complexes charges are exclusively located on C60 or C70 , while the charges reside on [10]CPP in the case of cationic complexes. [2 : 1] complexes of the ([10]CPP2 ⊃C60/70 )+ ⋅/- ⋅ type are observed for the first time as isolated solitary gas-phase species. Here, C60 -based [2 : 1] complexes are less stable than the respective C70 analogues. By virtue of the high stability of cationic [1 : 1] complexes, [2 : 1] complexes show a strongly reduced stability of the radical cations. DFT analyses of the minimum geometries as well as molecular dynamics calculations support the experimental data. Furthermore, our novel gas-phase [2 : 1] complexes are also found in 1,2-dichlorobenzene. Insights into the thermodynamic parameters of the binding process as well as the species distribution are derived from isothermal titration calorimetry (ITC) measurements.

Compositional Effect on the Low-Temperature Oxidation of Crude Oils Subjected to In Situ Combustion

This work shows the compositional effect on low-temperature oxidation of crude oils subjected to in situ combustion (ISC). Three heavy crudes were used in this study in which detailed information on the molecular species involved in ISC was obtained by ultra-high-resolution mass spectrometry. The oxidation was carried out on a mixture of 2% of crude oil in Ottawa sand in an isothermal cell using a batch system at 1500 psi at three conditions: (i) reservoir temperature of each crude oil, (ii) 180 °C, and (iii) 180 °C using a heterogeneous catalyst-type β-MnO2. The oil remaining after the reaction was extracted from the sand and characterized by FT-ICR MS using (+) atmospheric pressure photoionization and (−) electrospray ionization modes. The acidity of the oxidation products (extracts) and the composition of the produced carbon oxides were also monitored. A greater amount of carbon oxides produced, a lower extraction yield of organic matter in the sand after the reaction, and a higher acidity in the extracts, implied a higher reactivity. In the same sense, a higher reactivity was observed for the sample with the highest sulfur content and over the most aromatic compounds. The use of the catalyst at 180 °C promoted the oxidative reactions in two of three of the oils, as well as the formation of polyoxygenated acids over monocarboxylic acids for one of the oils, which implies that the application of this technology strongly depends on the composition of the oil.

Diversity of organic components in airborne waste discharged from sewer pipe repairs.

Air-discharged waste from commonly used trenchless technologies of sewer pipe repairs is an emerging and poorly characterized source of urban pollution. This study reports on the molecular-level characterization of the atmospherically discharged aqueous-phase waste condensate samples collected at four field sites of the sewer pipe repairs. The molecular composition of organic species in these samples was investigated using reversed-phase liquid chromatography coupled with a photodiode array detector and a high-resolution mass spectrometer equipped with interchangeable atmospheric pressure photoionization and electrospray ionization sources. The waste condensate components comprise a complex mixture of organic species that can partition between gas-, aqueous-, and solid-phases when water evaporates from the air-discharged waste. Identified organic species have broad variability in molecular weight, molecular structures, and carbon oxidation state, which also varied between the waste samples. All condensates contained complex mixtures of oxidized organics, N- and S-containing organics, condensed aromatics, and their functionalized derivatives that are directly released to the atmospheric environment during installations. Furthermore, semi-volatile, low volatility, and extremely low volatility organic compounds comprise 75-85% of the total compounds identified in the waste condensates. Estimates of the component-specific viscosities suggest that upon evaporation of water waste material would form the semi-solid and solid phases. The low volatilities and high viscosities of chemical components in these waste condensates will contribute to the formation of atmospheric secondary organic aerosols and atmospheric solid nanoplastic particles. Lastly, selected components expected in the condensates were quantified and found to be present at high concentrations (1-20 mg L-1) that may exceed regulatory limits.

Screening of Medicinal Compounds in Blood by Atmospheric Pressure Laser Plasma Ionization Mass Spectrometry

We proposed a procedure for screening drug compounds by high-resolution mass spectrometry with atmospheric pressure laser plasma ionization (APLPI). The analytical performance of the method was studied on examples of five medicinal compounds: Lidocaine, Bendazole, Papaverine, Chloropyramine, and Carbamazepine. Calibration dependences were obtained in the analysis of model solutions and blood samples; sensitivity coefficients were determined. The relative standard deviation of the results is in the range 20–27%. The APLPI technique can detect promptly and reliably the studied medicinal compounds at concentrations 0.5–6 ng/mL in a sample. The sensitivity of APLPI exceeds that of atmospheric pressure electrospray ionization by 4–16 times.

Bioanalytical method development and validation of atrasentan in human plasma using verapamil as internal standard by liquid chromatography coupled with tandem mass spectrometry

A satisfactory LC-MS/MS separation and good peak symmetry for Atrasentan were obtained with Agilent, Zorbax, XDB C18 (2.1 x 50 mm ID, 5 μm), and a mobile phase containing a mixture of 5 mM Ammonium Formate buffer with 0.1% formic acid were mixed with HPLC grade Acetonitrile in the proportion of 70:30, v/v was delivered at a flow rate of 0.150 mL/min by positive ion mode (API 4000) with an injection volume of 10 µL and a run time of 3 min. Detection is performed by atmospheric pressure electrospray ionization (ESI) mass spectrometry in positive ion mode. The precursor to product ion transitions is m/z 5.11.600 to 354.04 for Atrasentan, and m/z 455.40 to 165.00 for Verapamil (Internal standard) were used for quantization. The retention time of Atrasentan and Verapamil (Internal standard) was found to be 1.68 & 0.96 min.

Bioanalytical method development and validation of atrasentan in human plasma using verapamil as internal standard by liquid chromatography coupled with tandem mass spectrometry

A satisfactory LC-MS/MS separation and good peak symmetry for Atrasentan were obtained with Agilent, Zorbax, XDB C18 (2.1 x 50 mm ID, 5 μm), and a mobile phase containing a mixture of 5 mM Ammonium Formate buffer with 0.1% formic acid were mixed with HPLC grade Acetonitrile in the proportion of 70:30, v/v was delivered at a flow rate of 0.150 mL/min by positive ion mode (API 4000) with an injection volume of 10 µL and a run time of 3 min. Detection is performed by atmospheric pressure electrospray ionization (ESI) mass spectrometry in positive ion mode. The precursor to product ion transitions is m/z 5.11.600 to 354.04 for Atrasentan, and m/z 455.40 to 165.00 for Verapamil (Internal standard) were used for quantization. The retention time of Atrasentan and Verapamil (Internal standard) was found to be 1.68 & 0.96 min.

Development and validation of empagliflozin in human plasma using nevirapine as internal standard by liquid chromatography-tandem mass spectrometry

The present LC-MS/MS method for the estimation of Empagliflozin in human plasma by using Nevirapine as an internal standard was established and validated as per ICH guidelines. The best response was obtained with Phenomenex Synergi,4µm,4.6×75mm, and a mobile phase containing a mixture of 5mM Ammonium Acetate buffer with 0.1% Formic Acid: Acetonitrile (50:50 v/v) was delivered at a flow rate of 0.900 mL/min by positive ion mode (API 4000Q Trap) with an injection volume of 20 µL and a run time of 3 min. Detection is performed by atmospheric pressure electrospray ionization (ESI) tandem mass spectrometry in positive ion mode. The precursor to product ion transitions is m/z451.52>71.32 for Empagliflozin and m/z 267.3>226.8 for Nevirapine (Internal standard) were used for quantization. The retention time of Empagliflozin and Nevirapine (Internal standard) was found to be 1.50 min and 2.40 min respectively. Linearity was established for Empagliflozin in the range of 2.0pg/mL to 979.9pg/mL with a correlation coefficient (r=0.999) and the overall percentage recovery was 94.63 % for Empagliflozin and 91.94 % for Nevirapine (Internal standard) respectively.

Molecular Characterization of Formulated Lubricants and Additive Packages Using Kendrick Mass Defect Determined by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

Formulated lubricants correspond to high value products used for several applications in automotive, industrial, medicinal, and agro-food sectors. They correspond to complex matrices composed of approximately 80% of base oils (mineral or synthetic) and of about 20% of additives. Additives are generally low molecular weight polymeric molecules with a great diversity of elements. To characterize such complex compositions at the molecular level, ultrahigh resolution mass spectrometers are required. Two formulated lubricants and two additive packages were analyzed by Fourier transform ion cyclotron resonance mass spectrometry in direct infusion. Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) sources were used to have an exhaustive characterization of the samples. The Kendrick mass defects (KMD) plot is a widespread representation to characterize polymeric molecules. Here, the terms apparent mass defect and apparent Kendrick mass defects (aKMD) values were introduced to consider the uncertainty on nominal mass determination. Several additive families including alkyldiphenylamines, trisalkylphenylthiophosphoric acid, zinc dithiophosphates, bisuccinimide dispersants, and their derivatives were observed by APCI(+). ESI(-) also presented a use for the selective ionization of acidic compounds including sulfonates, phenates, and sulfur phenate molecules. The specific aKMD values and polydispersity of many additive families have been reported to create a database of additives. Overall, this study demonstrated the great utility of the aKMD approach and the use of the ESI/APCI combination for a simple and fast characterization of formulated lubricant and additive package samples.

Ultrahigh-performance supercritical fluid chromatography – mass spectrometry for the qualitative analysis of metabolites covering a large polarity range

The applicability of ultrahigh-performance supercritical fluid chromatography coupled with mass spectrometry (UHPSFC/MS) for the qualitative analysis of metabolites with a wide polarity range (log P: −3.89–18.95) was evaluated using a representative set of 78 standards belonging to nucleosides, biogenic amines, carbohydrates, amino acids, and lipids. The effects of the gradient shape and the percentage of water (1, 2, and 5%) were investigated on the Viridis BEH column. The screening of eight stationary phases was performed for columns with different interaction sites, such as hydrogen bonding, hydrophobic, π-π, or anionic exchange type interactions. The highest number of compounds (67) of the set studied was detected on the Torus Diol column, which provided a resolution parameter of 39. The DEA column had the second best performance with 58 detected standards and the resolution parameter of 54. The overall performance of other parameters, such as selectivity, peak height, peak area, retention time stability, asymmetry factor, and mass accuracy, led to the selection of the Diol column for the final method. The comparison of additives showed that ammonium acetate gave a superior sensitivity over ammonium formate. Moreover, the influence of the ion source on the ionization efficiency was studied by employing atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). The results proved the complementarity of both ionization techniques, but also the superior ionization capacity of the ESI source in the negative ion mode, for which 53% of the analytes were detected compared to only 7% for the APCI source. Finally, optimized analytical conditions were applied to the analysis of a pooled human plasma sample. 44 compounds from the preselected set were detected in human plasma using ESI-UHPSFC/MS in MSE mode considering both ionization modes.

Three-dimensional liquid chromatography with parallel second dimensions and quadruple parallel mass spectrometry for adult/infant formula analysis

Three dimensions of chromatographic separation, using split-flow two-dimensional liquid chromatography (SF-2D-LC) with two parallel second dimensions, LC × 2LC, combined with quadruple parallel mass spectrometry (LC3MS4) is demonstrated for analysis of NIST SRM 1849a adult/infant formula. The first dimension, 1D, was a conventional non-aqueous reversed-phase (NARP) HPLC separation using two C18 columns in series, followed by detection using an ultraviolet (UV) detector, a fluorescence detector (FLD), with flow then split to a corona charged aerosol detector (CAD), and then dual parallel mass spectrometry (MS), conducted in atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) modes. The first second dimension, 2D(1), UHPLC was conducted on a 50.0 mm C30 column using a NARP-UHPLC parallel gradient for separation of short-chain triacylglycerols (TAGs) from long-chain TAGs, with detection by UV and ESI-MS. The second dimension, 2D(2), UHPLC was conducted using a 100.0 mm C30 column with a NARP-UHPLC parallel gradient for improved separation of TAG isomers, with detection by UV, an evaporative light scattering detector, and high-resolution, accurate-mass (HRAM) ESI-MS. Transferred eluent dilution was used to refocus peaks and keep them sharp during elution in both 2Ds. The separation space in the 2D(2) was optimized using multi-cycle (aka, “constructive wraparound”) elution, which employed flow rate programming. In the 1D, calibration lines for quantification of fat-soluble vitamins were constructed. A lipidomics approach to TAG identification and quantification by HRAM-ESI-MS was applied to the 2D(2). These experiments can be represented: LC1MS2 × (LC1MS1 + LC1MS1) = LC3MS4, or three-dimensional liquid chromatography with quadruple parallel mass spectrometry.

Studying the Complexity of Biomass Derived Biofuels

Biofuel produced from biomass pyrolysis is a good example of a highly complex mixture. Detailed understanding of its composition is a prerequisite for optimizing transformation processes and further upgrading conditions. The major challenge in understanding the composition of biofuel derived from biomass is the wide range of compounds with high diversity in polarity and abundance that can be present. In this work, a comprehensive analysis using mass spectrometry is reported. Different operation conditions are studied by utilizing multiple ionization methods (positive mode atmospheric pressure photo ionization (APPI), atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) and negative mode ESI) and applying different resolving power set-ups (120 k, 240 k, 480 k and 960 k) and scan techniques (full scan and spectral stitching method) to study the complexity of a pyrolysis biofuel. Using a mass resolution of 960 k and the spectral stitching scan technique gives a total of 21,703 assigned compositions for one ionization technique alone. The number of total compositions is significantly expanded by the combination of different ionization methods.

Surrogate formulation and molecular characterization of sulfur species in vacuum residues using APPI and ESI FT-ICR mass spectrometry

Vacuum residues (VR) are the bottom of the barrel products left after vacuum distillation of crude oils. VR are primarily used as feedstock for production of syn-gas and hydrogen via gasification; and heavy fuel oil (HFO) for use as fuel in power generation and shipping. However, VR contain relatively large amounts of sulfur (upto 8% by mass) and require the removal of varying amounts depending on the emission norms (eg. International Maritime Organization 2020 sulfur regulations). Understanding the fuel molecular structure and, in particular, the structure of sulfur species enables the adoption and optimization of suitable desulfurization strategies. In the present work, detailed molecular characterization of the sulfur species in VR was performed using positive ion atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) coupled to Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS). Ions possessing mass to charge (m/z) in the range of 100 to 1200 were detected using the ultra-high resolution instrument and were resolved into unique chemical formulas (CcHhSsNnOo). The assigned masses were then divided into molecular classes based on the presence of heteroatoms, and plots of carbon number versus double bond equivalency (DBE) were made for each molecular class. The molecular classes were further sub-divided based on the presence of sulfur families like sulfides (Su), thiophenes (Th), benzothiophenes (BT), dibenzothiophenes (DBT) and benzonaphthothiophene (BNT) and their derivatives. A single surrogate molecule that represents the average structure of the VR sample was then designed based on the average molecular parameters (AMP) obtained from APPI and ESI FT-ICR MS. Plausible core skeletal structures of VR were drawn from the average DBE value, and then a symmetrical, alkylated, polyaromatic sulfur heterocycles (PASH) molecule was formulated as the VR surrogate. A number of physical and thermo-chemical properties of the VR surrogate were then predicted using quantitative structure property relationships (QSPR). The VR surrogate proposed here will enable high-fidelity computational studies, including chemical kinetic modeling, property estimation, and emissions modeling.

Determination of selected water-soluble vitamins (thiamine, riboflavin, nicotinamide and pyridoxine) from a food matrix using hydrophilic interaction liquid chromatography coupled with mass spectroscopy

Water-soluble vitamins are essential dietary components with a multitude of important functions that require quantification from food sources to characterise the nutritional status of food. In this study, we have developed a hydrophilic interaction chromatography (HILIC) based method coupled to single-quadrupole mass spectrometry (MS) for the analysis of selected water-soluble vitamins. Due to their involvement in energy release from macronutrients, the quantification of thiamine (B1), riboflavin (B2), nicotinamide (B3) and pyridoxine (B6) offers significant value in food analysis.A commercially available vegetable soup was selected as the food matrix for this study and utilised to develop an efficient extraction procedure for the vitamins of interest. Vitamins were extracted using meta-phosphoric acid coupled with a reducing agent, DL-dithiothreitol (DTT) to produce the parent compound. The extracted vitamins were then analysed using an LC-MS system with electrospray – atmospheric pressure ionization (ES-API) source, operated in positive single ion monitoring (SIM) mode. The MS provided good linearity within the investigated range from 5 to 400 ng/mL with coefficient of determination (r2) ranging from 0.98 to 0.99. Retention times (0.65–9.04 min) were reproducible and no coelution between vitamins was observed. Limit of detection (LOD) varied from 2.4 to 9.0 ng/mL and limit of quantification (LOQ) was from 8 to 30 ng/mL, comparable to previously published studies. The extraction method provided good intra-day (%CV 1.56–6.56) and inter-day precision (%CV 8.07–10.97). Standard injections were used as part of quality control measures and provided excellent reproducibility (%CV 0.9–3.4). The overall runtime of this method was 19 min, including column reconditioning. Using this method, the quantity of thiamine (67 ± 7 ng/g), riboflavin (423 ± 39 ng/g), nicotinamide (856 ± 77 ng/g) and pyridoxine (133 ± 11 ng/g) was determined from a complex food matrix.In conclusion, we have developed a rapid and reliable, HILIC-single quad MS method utilising SIM for the low-level quantification of four B vitamins in a vegetable soup matrix in under 20 min. This method has shown excellent linearity, intra- and inter-day reproducibility and is directly applicable to other plant-based food matrices.

Top-down lignomics analysis of the French oak lignin by atmospheric pressure photoionization and electrospray ionization quadrupole time-of-flight tandem mass spectrometry: Identification of a novel series of lignans.

We report herein the top-down lignomic analysis of virgin released lignin (VRL) extracted from the French oak wood using atmospheric pressure photoionization quadrupole orthogonal time-of-flight mass spectrometry (APPI-QqTOF-MS) (+ ion mode). Eight major protonated lignin oligomers were identified using the APPI-QqTOF-MS/MS of this complex VRL mixture without any kind of purification. This series of protonated oligomer ions were identified as neolignan cedrusin (1), five different aryltetralin lignans dimers (2-6), one lignan-dehydroshikimic acid complex (7), and a lignan trimer (8). Similarly, electrospray ionization (ESI)-QqTOF-MS (+ ion mode) allowed us to identify three extra aryltetralin lignan derivatives (9-11). The Kendrick mass defect analysis was used for the simplification of this complex APPI-QqTOF-MS into a compositional map, which displayed clustering points of associated ions possessing analogous elemental composition. This series of novel protonated molecules were selected and subjected to low-energy collision-induced dissociation (CID)-MS/MS analyses. The obtained gas-phase fragmentation patterns helped to tentatively assign their most likely structures. Also, it was found that the use of different APPI and ESI ambient ionization techniques enhances the ionization of different types of lignin oligomers.

Features of recording the analytical signal of beryllium using APESI mass-spectrometry and different procedures of sample preparation

The significance of the problem of determining the concentration of beryllium in solutions is substantiated. A method of APESI mass-spectrometry (atmospheric pressure electrospray ionization with in-source atomization) is compared with a number of other common procedures used for solving the aforementioned problem and a number of advantages of APESI mass spectrometry are highlighted. The possibility of measuring the beryllium concentration in various chemical forms using APESI mass-spectrometry is studied. We used sulfate, nitric acid and chloride salts of beryllium. The measurements were carried out on a specialized small-sized mass spectrometer MI-20 «LowMass» developed at MS-Bio Company, Russia. A schematic diagram of the device designed to determine the concentration of beryllium in solutions is presented and described. A technique of solution preparation and measurement procedure are proposed. Presented ass spectra obtained on the samples containing beryllium and lithium isotopes were used as an internal standard. It is shown that beryllium can be detected from the salts of chloride and nitric acids with close relative sensitivity coefficients. The obtained detection limit for beryllium chloride in those measurements was ~1 – 2 × 10–8 M. At the same time, the analytical signal of beryllium cannot be detected during electrospray of the solution of beryllium sulfate under any experimental conditions. It has been suggested that this effect may be attributed to the features of dissolution of beryllium sulfate, in particular, to hydrolysis and formation of complex compounds with sulfate, including complex polymer and colloidal forms.

Expanded coverage of non-targeted LC-HRMS using atmospheric pressure chemical ionization: a case study with ENTACT mixtures.

Non-targeted analysis (NTA) is a rapidly evolving analytical technique with numerous opportunities to improve and expand instrumental and data analysis methods. In this work, NTA was performed on eight synthetic mixtures containing 1264 unique chemical substances from the U.S. Environmental Protection Agency's Non-Targeted Analysis Collaborative Trial (ENTACT). These mixtures were analyzed by atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) using both positive and negative polarities for a total of four modes. Out of the 1264 ENTACT chemical substances, 1116 were detected in at least one ionization mode, 185 chemicals were detected using all four ionization modes, whereas 148 were not detected. Forty-four chemicals were detected only by APCI, and 181 were detected only by ESI. Molecular descriptors and physicochemical properties were used to assess which ionization type was preferred for a given compound. One ToxPrint substructure (naphthalene group) was found to be enriched in compounds only detected using APCI, and eight ToxPrints (e.g., several alcohol moieties) were enriched in compounds only detected using ESI. Examination of physicochemical parameters for ENTACT chemicals suggests that those with higher aqueous solubility preferentially ionized by ESI-. While ESI typically detects a larger number of compounds, APCI offers chromatograms with less background, fewer co-elutions, and additional chemical space coverage, suggesting both should be considered for broader coverage in future NTA research. Graphical abstract.

Simultaneous total analysis of core and polar membrane lipids in archaea by high-performance liquid chromatography/high-resolution mass spectrometry coupled with heated electrospray ionization.

Archaea have characteristic membrane lipids including diether and/or tetraether isoprenoidal core lipids with various polar head groups. Since the polar group is removed soon after the end of archaeal activity, the occurrences of core and polar lipids are regarded as dead and active signals, respectively. The core and polar lipids have generally been analyzed separately using atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), respectively, coupled with mass spectrometry. In this study, simultaneous analyses of core and polar archaeal lipids have been examined using heated electrospray ionization (HESI) by high-performance liquid chromatography/high-resolution mass spectrometry (HPLC/HRMS). Both core and intact polar lipids can be analyzed simultaneously by HESI with good sensitivity (sub ng to 100 ng) and separation using a semi-bore diol column by normal-phase chromatography. The core lipids eluted firstly to separate archeaol, then glycerol dibiphytanyl glycerol tetraethers (GDGTs), followed by the polar lipids with glycosides and glycophosphates. The relative GDGT composition is identical between HESI and APCI methods. The simultaneous analysis has the benefit of minimizing sample amount and elution solvent as well as preparation work. The method can also be applied to a compound class fractionation for compound-specific carbon and hydrogen isotope analysis.

Profiling Murchison Soluble Organic Matter for New Organic Compounds with APPI- and ESI-FT-ICR MS.

The investigation of the abundant organic matter in primitive meteorite such as carbonaceous chondrites is of major interest in the field of origin of life. In this study, the soluble organic fraction of the Murchison meteorite was analyzed by atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), in both detection modes. Such an approach ensured that we obtained an extensive description of the organic matter of the CM2 meteorite. Indeed, while in total close to 16,000 unique features were assigned, only 4% are common to all analyses, illustrating the complementarity of both the detection modes and the ionization sources. ESI FT-ICR MS analysis, in negative-ion mode, ensured to observe specifically CHOS and CHNOS species, whereas the positive-ion mode is more dedicated to the detection of CHNO and CHN species. Moreover, new organomagnesium components were observed in (+) ESI. Eventually, (+) APPI FT-ICR MS analysis was a preferred method for the detection of less polar or nonpolar species such as polycyclic aromatic hydrocarbons but also heteroatom aromatic species composing the organic matter of Murchison.