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Charge-transfer interactions are often assumed to be dominant among the noncovalent interactions that govern the solute retention in electron donor-acceptor chromatography. This popular view, however, has been called into question by recent studies that suggest an important role for electrostatic interactions in the formation of donor-acceptor complexes. We reported here an experimental investigation concerning the question as to whether charge-transfer or electrostatic interactions are the driving force for solute retention in donor-acceptor chromatography. Using three chromatographic systems composed of a dinitrobenzene derived stationary phase and a hexane based mobile phase, we determined retention factors for a range of aliphatic and aromatic hydrocarbons and correlated them with molecular properties that describe the solute's dispersion, charge-transfer, and electrostatic characteristics. It was found that the molecular polarizability and ionization potential give either very poor or no correlation with solute retention whereas the molecular quadrupole moment is a linear function of the logarithmic retention factor. These results were interpreted as showing that electrostatic, rather than charge-transfer or dispersion, interactions play a major role in determining solute retention. The dominance of the electrostatic interactions over the other noncovalent interactions was discussed in terms of distance dependency of the interaction energy. [ABSTRACT FROM AUTHOR]

The retention mechanism of aromatic hydrocarbons in normal phase liquid chromatography has been investigated with respect to the dominant molecular interactions between the polar stationary phase and the solute. The retention behavior of these aromatic solutes is compared with that of aliphatic hydrocarbons with similar molecular polarizability, and the difference between them is interpreted in terms of relative contributions of dispersion, induction and electrostatic interactions to the observed retention. While the aliphatic hydrocarbons are unretained in all of the chromatographic systems studied, the aromatic hydrocarbons show increasing retention with their molecular quadrupole moments. This is consistent with a retention model in which the electrostatic interactions that involve a solute quadrupole moment play a major role in controlling the retention of aromatic hydrocarbons in normal phase liquid chromatography. [ABSTRACT FROM AUTHOR]

Fragmentation reactions of both metastable and collisionally activated dications, formed by electron impact ionization of heterocyclic fused-ring aromatic compounds containing more than one nitrogen atom, were investigated. This work is an extension of similar work on analogous compounds containing just one nitrogen atom and on the related polycyclic aromatic hydrocarbons. The results obtained are interpreted in terms of mechanistic proposals concerning the competition between charge-separation and neutral-expulsion reactions, based on variations in diradical character with increasing molecular size and nitrogen content of these molecular dications. [ABSTRACT FROM AUTHOR]

Palytoxin (PlTX) is one of the most toxic non-protein molecules extracted from soft corals, posing significant risks within the food chain. To mitigate these risks, regulatory agencies prioritize developing reliable analytical techniques for monitoring and risk management of PlTX in marine organisms. The analysis of PlTX using liquid chromatography-tandem mass spectrometry (LC/MS/MS) has become a preferred method due to its high sensitivity and specificity. However, previous studies have reported challenges in achieving sharp peak shapes and adequate resolution in PlTX detection, which can compromise the accuracy and reliability of quantification. Therefore, PlTX monitoring is actively performed using an emerging and enhanced LC/MS/MS method. To ensure accurate quantification of PlTX, which is present in trace amounts in marine organisms, it is essential to optimize chromatographic separation and ionization. In this study, we optimized the separation conditions to improve PlTX quantification through the adjustment of a buffer system, specifically increasing the concentration of ammonium formate using reverse-phase liquid chromatography coupled with multiple reaction-monitoring mass spectrometry (RPLC/MRM-MS). This optimization significantly improved peak sharpness and resolution, enhancing the overall analytical performance of LC–MS/MS for PlTX detection in marine samples. Our findings suggest that the optimized method can serve as a reliable reference for developing standardized protocols aimed at improving PlTX analysis. [ABSTRACT FROM AUTHOR]

Thlaspi arvense (Pennycress) is an emerging feedstock for biofuel production because of its high seed oil content enriched in erucic acid. A transcriptomic and a lipidomic study were performed to analyze the dynamics of gene expression, glycerolipid content and acyl-group distribution during seed maturation. Genes involved in fatty acid biosynthesis were expressed at the early stages of seed maturation. Genes encoding enzymes of the Kennedy pathway like diacylglycerol acyltransferase1 (TaDGATl), lysophosphatidic acid acyltransferase (TaLPAT) or glycerol 3-phosphate acyltransferase (TaGPAT) increased their expression with maturation, coinciding with the increase in triacylglycerol species containing 22:1. Positional analysis showed that the most abundant triacylglycerol species contained 18:2 at sn-2 position in all maturation stages, suggesting no specificity of the lysophosphatidic acid acyltransferase for very long chain fatty acids. Diacylglycerol acyltransferase2 (TaDGAT2) mRNA was more abundant at the initial maturation stages, coincident with the rapid incorporation of 22:1 to triacylglycerol, suggesting a coordination between Diacylglycerol acyltransferase enzymes for triacylglycerol biosynthesis. Genes encoding the phospholipid-diacylglycerol acyltransferase (TaPDAT1), lysophosphatidylcholine acyltransferase (TaLPCAT) or phosphatidylcholine diacylglycerolcholine phosphotransferase (TaPDCT), involved in acyl-editing or phosphatidyl-choline (PC)-derived diacylglycerol (DAG) biosynthesis showed also higher expression at the early maturation stages, coinciding with a higher proportion of triacylglycerol containing C18 fatty acids. These results suggested a higher contribution of these two pathways at the early stages of seed maturation. Lipidomic analysis of the content and acyl-group distribution of diacylglycerol and phosphatidyl-choline pools was compatible with the acyl content in triacylglycerol at the different maturation stages. Our data point to a model in which a strong temporal coordination between pathways and isoforms in each pathway, both at the expression and acyl-group incorporation, contribute to high erucic triacylglycerol accumulation in Pennycress. [ABSTRACT FROM AUTHOR]

Online monitoring of dynamic chemical processes involving a wide volatility range of hydrocarbon species is challenging due to long chromatographic measurement times. Mass spectrometry (MS) overcomes chromatographic delays. However, the analysis of n-alkane mixtures by MS is difficult because many fragment ions are formed, which leads to overlapping signals of the homologous series. Atmospheric pressure chemical ionization (APCI) is suitable for the analysis of saturated hydrocarbons and is the subject of current research. Still, although APCI is a "soft ionization" technique, fragmentation is typically inevitable. Moreover, it is usually applied for liquid samples, while an application for online gas-phase monitoring is widely unexplored. Here, we present an automated APCI-MS method for an online gas-phase analysis of volatile and semi-volatile n-alkanes. Mass spectra for n-heptane and n-decane reveal [M-H]+, [M-3H]+ and [M-3H+H2O]+ as abundant ions. While [M-H]+ and [M-3H]+ show an excessive fragmentation pattern to smaller CnH2n+1+ and CnH2n-1+ cations, [M-3H+H2O]+ is the only relevant signal within the CnH2n+1O+ ion group, i.e., no chain cleavage is observed. This makes [M-3H+H2O]+ an analyte-specific ion that is suitable for the quantification of n-alkane mixtures. A calibration confirms the linearity of C7 and C10 signals up to concentrations of ~1000–1500 ppm. Moreover, validated concentration profiles are measured for a binary C7/C10 mixture and a five-alkane C7/C10/C12/C14/C20 mixture. Compared to the 40-min sampling interval of the reference gas chromatograph, MS sampling is performed within 5 min and allows dynamic changes to be monitored. [ABSTRACT FROM AUTHOR]

Natural abundance and isotopically labelled tryptic peptides are routinely employed as standards in quantitative proteomics. The certification of the peptide content is usually carried out by amino acid analysis using isotope dilution mass spectrometry (IDMS) after the acid hydrolysis of the peptide. For the validation and traceability of the amino acid analysis procedure, expensive certified peptides must be employed. In this work we evaluate different IDMS alternatives which will reduce the amount of certified peptide required for validation of the amino acid analysis procedure. In this context, the characterization of both natural and isotopically labelled synthetic angiotensin I peptides was carried out. First, we applied a fast procedure for peptide hydrolysis based on microwave-assisted digestion and employed two certified peptide reference materials SRM 998 angiotensin I and CRM 6901-b C-peptide for validation of the hydrolysis procedure. The amino acids proline, leucine, isoleucine, valine, tyrosine, arginine and phenylalanine were evaluated for their suitability for peptide certification by IDMS by both liquid chromatography with tandem mass spectrometry (LC–MS/MS) and gas chromatography with mass spectrometry (GC)–MS/MS. Then, natural angiotensin I and 13C1-labelled angiotensin I were synthesized in-house and purified by preparative liquid chromatography. The concentration of the 13C1-labelled angiotensin I peptide was established by reverse IDMS in its native form using SRM 998 angiotensin I as reference. The concentration of the natural synthesized peptide was determined by IDMS both using the 13C1-labelled peptide in its native form and by amino acid analysis showing comparable results. Finally, the synthetic naturally abundant angiotensin I peptide was employed as "in-house" standard for the validation of subsequent peptide characterization procedures. Therefore, the novelty of this work relies on, first, the development of a faster hydrolysis procedure assisted by focused microwaves, providing complete hydrolysis in 150 min, and secondly, a validation strategy combining GC–MS and LC–MS/MS that allowed us to certify the purity of an in-house-synthesized peptide standard that can be employed as quality control in further experiments. [ABSTRACT FROM AUTHOR]

Soil is a vital component of the ecosystem that drives the holistic homeostasis of the environment. Directly, soil quality and health by means of sufficient levels of soil nutrients are required for sustainable agricultural practices for ideal crop yield. Among these groups of nutrients, soil carbon is a factor which has a dominating effect on greenhouse carbon phenomena and thereby the climate change rate and its influence on the planet. It influences the fertility of soil and other conditions like enriched nutrient cycling and water retention that forms the basis for modern 'regenerative agriculture'. Implementation of soil sensors would be fundamentally beneficial to characterize the soil parameters in a local as well as global environmental impact standpoint, and electrochemistry as a transduction mode is very apt due to its feasibility and ease of applicability. Organic Matter present in soil (SOM) changes the electroanalytical behavior of moieties present that are carbon-derived. Hence, an electrochemical-based 'bottom-up' approach is evaluated in this study to track soil organic carbon (SOC). As part of this setup, soil as a solid-phase electrolyte as in a standard electrochemical cell and electrode probes functionalized with correlated ionic species on top of the metalized electrodes are utilized. The surficial interface is biased using a square pulsed charge, thereby studying the effect of the polar current as a function of the SOC profile. The sensor formulation composite used is such that materials have higher capacity to interact with organic carbon pools in soil. The proposed sensor platform is then compared against the standard combustion method for SOC analysis and its merit is evaluated as a potential in situ, on-demand electrochemical soil analysis platform. [ABSTRACT FROM AUTHOR]

Abstract—The kinetic laws of Fe3+ ion electroreduction in the KCl–NaCl–CsCl eutectic melt at 823 K are determined. The potentials of metallic iron and dysprosium formation on the inert tungsten electrode in the KCl–NaCl–CsCl molten system are found to differ by approximately 1.5 V. In the case of the combined presence of Fe3+ and Dy3+ ions in the KCl–NaCl–CsCl eutectic melt, a certain depolarization of dysprosium ion electroreduction occurs on the metallic iron preliminary deposited at the tungsten electrode to form iron- and dysprosium-based intermetallic phases of different compositions. The dissolution potentials of the different intermetallic phases DyxFey are determined by open circuit chronopotentiometry. [ABSTRACT FROM AUTHOR]

Supercritical fluid chromatography (SFC) is a promising alternative to conventional chromatographic methods and has several advantages over them in selectivity, efficiency, speed of separation, and environmental friendliness. Its combination with atmospheric pressure chemical ionization (APCI) mass spectrometric detection is one of the central areas of method development and requires an understanding of the APCI specificity in using carbon dioxide-based mobile phases. In the present study, the composition of negatively charged ions formed under APCI conditions for carbon dioxide–organic modifier (methanol, isopropanol, acetonitrile) systems, and also the influence of the mobile phase and ion source parameters (corona discharge needle voltage, temperature) on it are studied using high-resolution mass spectrometry. The results obtained testify to a significant role of carbon dioxide as a direct precursor for the formation of reaction particles (hydrocarbonate and percarbonate anions, carbonate radical anion) and as a reagent capable of shifting the ion-molecular equilibrium in corona discharge plasma and forming compounds with the organic modifier (alkylcarbonic acid anions in the case of alcohols, adduct with a deprotonated acetonitrile molecule). Ion-molecular equilibria involving carbon dioxide result in the formation of a large number of reactive particles that can take part in the ionization processes of analytes in SFC–APCI-MS. [ABSTRACT FROM AUTHOR]

Dinitrotoluenes (DNTs) and nitrotoluenes (NTs) are found in the environment as metabolites of trinitrotoluene (TNT). When acetone is used as the solvent/eluent in atmospheric pressure chemical ionization‐mass spectrometry (APCI‐MS), the reactant ion is [2Acetone + O2]•− for the negative ion mode. The reactant ion reacts with an analyte to produce M•− and/or [M – H]− under atmospheric pressure. In this study, ionization behaviors of NT (2‐, 3‐, and 4‐NTs) and DNT isomers (2,3‐, 2,4‐, and 2,6‐DNTs) by reactions with [2Acetone + O2]•− were investigated. The energy‐minimized structures of the product ions and their energies were calculated to explain the differences in the ionization behaviors. Typical NT‐ and DNT‐related ions were produced by reactions with [2Acetone + O2]•−; NT•−, [NT – H]−, DNT•−, [DNT – H]−, and [DNT – NO]− ions. The ionization efficiencies of NT‐ and DNT‐related ions increased by increasing the source fragmentor voltage, and those of DNT‐related ions were higher than those of the NT‐related ions owing to the presence of an additional nitro group. The ionization efficiency of 3‐NT•− was higher than that of [NT – H]−, while that of [DNT – H]− was higher than those of DNT•− and [DNT – NO]−. The ionization efficiency order of NT•− was 3‐NT > 4‐NT > 2‐NT, while that of [DNT – H]− was 2,4‐DNT > 2,6‐DNT > 2,3‐DNT. The [NT – H]− and [DNT – H]− ions were stabilized by resonance structures containing nitro groups. The [DNT – NO]− ions were formed through the transition state. [ABSTRACT FROM AUTHOR]

An instrumental neutron activation analysis method in conjunction with Compton suppression spectrometry was developed for the simultaneous determination of nanogram levels of Cl, Br and I in salmon muscle and skin. Several non-chlorinated solvent systems were evaluated for the extraction of lipids containing organohalogens and an acetone-hexane (1:1) system was selected because it gave the highest extraction efficiency with least contamination. An extensive quality assurance program was designed. Lipid fractionation procedures were developed using size exclusion, solid phase extraction and thin layer chromatography followed by characterization using 1H, 13C and 31P nuclear magnetic resonance and mass spectrometry. Results show that both muscle and skin had high levels of triacylglycerols. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of acetonitrile to ethylamine with a high selectivity is a novel approach to manufacture valuable primary amines which are important raw material in organic chemical industry. However, the poor ethylamine Faradic efficiency (FEethylamine) and catalyst stability at the high current density prohibit this method from being practically used. Herein, CuNi alloy ultrafine-nano-particles based on the d-orbital coupling modulation were synthesized through the electrodeposition and their catalytic performance towards acetonitrile reduction reaction (ACNRR) has been systematically studied. The highest FEethylamine (97%) is achieved with the current density of −114 mA cm−2. For practical application, the current density can reach −602.8 mA cm−2 with 82.8% FEethylamine maintained. With the appearance of other organics which co-exist with acetonitrile in the SOHIO process, CuNi can also hydrogenate acetonitrile in it with more than 80% FEethylamine. Our in-situ spectroscopy analysis and DFT calculations towards the acetonitrile hydrogenation behavior reveal that the evenly dispersed Ni in Cu modulates the d-band so as to endow CuNi with the better acetonitrile adsorption, milder binding energy with the reaction intermediates, smaller barrier for *CH3CH2NH2 desorption and higher ability for H2O dissociation to provide *H. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of dysprosium ions, as well as dysprosium and nickel ion co-reduction, on inert tungsten electrodes and active nickel electrodes were studied in the eutectic KCl-NaCl-CsCl melt at a temperature of 823 K using the methods of cyclic and square-wave voltammetry and open circuit chronopotentiometry. The process of Dy3+ ions electroreduction was found to be reversible and to proceed within a single three-electron stage up to the polarization rate of 0.1 V/s. The increase in the polarization rate indicates a slower rate of the charge transfer, which causes the quasi-reversible character of the charge transfer. It is shown that when the KCl-NaCl-CsCl eutectic melt contains both nickel and dysprosium ions, the voltammetry curves at 823 K have a wave of nickel ion reduction at the potentials of −(0.22–0.28) V and a dysprosium ion reduction at the potentials of −(2.175–2.250) V relative to a chlorine-silver reference electrode. Apart from these waves, the voltammograms have two reduction waves at the potentials of −(1.9–1.95) V and −(2.05–2.1) V. These waves are associated with the reduction of dysprosium ions and their depolarization on metallic nickel, which was preliminary deposited on the tungsten electrode, as well as the formation of the intermetallic phases of dysprosium and nickel of various DyxNiy compositions. The (E-t) dependencies of the open circuit chronopotentiometry elucidate plateaus of the potential delay, which correspond to the dissolution of separate dysprosium and nickel intermetallic phases. Based on the results of the voltammetry changes and the chronopotentiometry of the open circuit, a series of electrochemical syntheses were performed in the potentiostatic regime at the potentials of −(1.7–2.1) V. The intermetallic phases of DyNi5, DyNi3 and DyNi2 were obtained at a definite ratio of the dysprosium and nickel chloride concentrations in the KCl-NaCl-CsCl eutectic melt and at a temperature of 823 K. The synthesized intermetallic samples were characterized by X-ray diffraction and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Electrochemical methods have been widely applied to measure fundamental data of element ions in molten salts. However, most applications neglected the fundamental premises and assumptions, which could lead to inaccurate results. This study provides a critical review on the methods and examines the limitation of each method in molten salt systems. The important parameters discussed in this work include electron transfer number, diffusion coefficient, formal potential, exchange current density, and charge transfer coefficient. Furthermore, the study discusses good practices to improve and proper applications to obtain accurate data. [ABSTRACT FROM AUTHOR]

This Tutorial is to provide a summary of parameters useful for successful outcomes of laserspray ionization (LSI) and related methods that employ a laser to ablate a matrix:analyte sample to produce highly charged ions. In these methods the purpose of the laser is to transfer matrix‐analyte clusters into the gas phase. Ions are hypothesized to be produced by a thermal process where emitted matrix:analyte gas‐phase particles/clusters are charged and loss of matrix from the charged particles leads to release of the analyte ions into the gas phase. The thermal energy responsible for the charge‐separation process is relatively low and not necessarily supplied by the laser; a heated inlet tube linking atmospheric pressure with the first vacuum stage of a mass spectrometer is sufficient. The inlet becomes the "ion source", and inter alia, pressure, temperature, and the matrix, which can be a solid, liquid, or combinations, become critical parameters. Injecting matrix:analyte into a heated inlet tube using laser ablation, a shockwave, or simply tapping, all produce the similar mass spectra. Applications are provided that showcase new opportunities in the field of mass spectrometry. [ABSTRACT FROM AUTHOR]

Surfactants are surface‐active agents widely used in numerous applications in our daily lives as personal care products, domestic, and industrial detergents. To determine complex mixtures of surfactants and their degradation products, unselective and rather insensitive methods, based on colorimetric and complexometric analyses are no longer employable. Analytical methodologies able to determine low concentration levels of surfactants and closely related compounds in complex matrices are required. The recent introduction of robust, sensitive, and selective mass spectrometry (MS) techniques has led to the rapid expansion of the surfactant research field including complex mixtures of isomers, oligomers, and homologues of surfactants as well as their chemically and biodegradation products at trace levels. In this review, emphasis is given to the state‐of‐the‐art MS‐based analysis of surfactants and their degradation products with an overview of the current research landscape from traditional methods involving hyphenate techniques (gas chromatography‐MS and liquid chromatography‐MS) to the most innovative approaches, based on high‐resolution MS. Finally, we outline a detailed explanation on the utilization of MS for mechanistic purposes, such as the study of micelle formation in different solvents. [ABSTRACT FROM AUTHOR]

Abstract—The electrochemical behavior of neodymium ions and their combined electroreduction with nickel ions at inert tungsten and active nickel electrodes are studied in the KCl–NaCl–CsCl eutectic melt at 823 K using cyclic voltammetry, square-wave voltammetry, chronopotentiometry, and open-circuit chronopotentiometry. The electroreduction of Nd3+ ions occurs reversibly in one three-electron step at polarization rates lower than 0.1 V/s. An increase in the polarization rate makes it possible to reveal that the charge-transfer step is retarded and becomes quasi-reversible. In the presence of both neodymium and nickel ions in the KCl–NaCl–CsCl eutectic melt at 823 K, voltammetry dependences show a nickel ion reduction wave at potentials from –0.18 to –0.23 V and a neodymium ion reduction wave at potentials from –2.16 to –2.22 V vs. silver chloride reference electrode. In addition to these waves, voltammograms have three reduction waves at potentials from –1.65 to –1.75 V, from –1.95 to –2.0 V, and from –2.07 to –2.12 V. These waves appear due to the combined electroreduction of neodymium and nickel ions on metallic nickel preliminary deposited on the tungsten electrode with a certain depolarization and formation of intermetallic phases of neodymium and nickel of various compositions (NdxNiy). Open-circuit chronopotentiometry dependences reveal a potential delay plateau corresponding to the dissolution of individual phases of neodymium and nickel intermetallic compounds. A series of electrochemical syntheses have been conducted in the potentiostatic mode at potentials from –1.8 to –2.2 V on the basis of the results of voltammetry measurements and open-circuit chronopotentiometry. At a certain ratio of concentrations of neodymium and nickel chlorides in the KCl–NaCl–CsCl eutectic melt at 823 K, the intermetallic phases NdNi5, NdNi3, and NdNi2 are formed. The synthesized samples of neodymium and nickel intermetallic compounds are characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy. The emf values of the NdxNiy intermetallic compounds are measured in the two-phase coexisting states at 823 K. The relative partial molar free Gibbs energy and the activity of neodymium in the NdxNiy intermetallic compounds are calculated from the determined values of emf. [ABSTRACT FROM AUTHOR]

Glycosylation is the most prevalent protein post‐translational modification, with a quarter of glycosylated proteins having enzymatic properties. Yet, the full impact of glycosylation on the protein structure–function relationship, especially in enzymes, is still limited. Here, we show that glycosylation rigidifies the important commercial enzyme horseradish peroxidase (HRP), which in turn increases its turnover and stability. Circular dichroism spectroscopy revealed that glycosylation increased holo‐HRP's thermal stability and promoted significant helical structure in the absence of haem (apo‐HRP). Glycosylation also resulted in a 10‐fold increase in enzymatic turnover towards o‐phenylenediamine dihydrochloride when compared to its nonglycosylated form. Utilising a naturally occurring site‐specific probe of active site flexibility (Trp117) in combination with red‐edge excitation shift fluorescence spectroscopy, we found that glycosylation significantly rigidified the enzyme. In silico simulations confirmed that glycosylation largely decreased protein backbone flexibility, especially in regions close to the active site and the substrate access channel. Thus, our data show that glycosylation does not just have a passive effect on HRP stability but can exert long‐range effects that mediate the 'native' enzyme's activity and stability through changes in inherent dynamics. [ABSTRACT FROM AUTHOR]

The combined use of hydrogen/deuterium exchange (HDX) and mass spectrometry (MS), referred to as HDX‐MS, is a powerful tool for exploring molecular edifices and has been used for over 60 years. Initially for structural and mechanistic investigation of low‐molecular weight organic compounds, then to study protein structure and dynamics, then, the craze to study small molecules by HDX‐MS accelerated and has not stopped yet. The purpose of this review is to present its different facets with particular emphasis on recent developments and applications. Reversible H/D exchanges of mobilizable protons as well as stable exchanges of non‐labile hydrogen are considered whether they are taking place in solution or in the gas phase, or enzymatically in a biological media. Some fundamental principles are restated, especially for gas‐phase processes, and an overview of recent applications, ranging from identification to quantification through the study of metabolic pathways, is given. [ABSTRACT FROM AUTHOR]

Understanding the biotransformation mechanisms of toxic sulfur-containing polycyclic aromatic hydrocarbon (PASH) pollutants such as benzothiophene (BT) is useful for predicting their environmental fates. In the natural environment, nondesulfurizing hydrocarbon-degrading bacteria are major active contributors to PASH biodegradation at petroleum-contaminated sites; however, BT biotransformation pathways by this group of bacteria are less explored when compared to desulfurizing organisms. When a model nondesulfurizing polycyclic aromatic hydrocarbon-degrading soil bacterium, Sphingobium barthaii KK22, was investigated for its ability to cometabolically biotransform BT by quantitative and qualitative methods, BT was depleted from culture media but was biotransformed into mostly high molar mass (HMM) hetero and homodimeric ortho-substituted diaryl disulfides (diaryl disulfanes). HMM diaryl disulfides have not been reported as biotransformation products of BT. Chemical structures were proposed for the diaryl disulfides by comprehensive mass spectrometry analyses of the chromatographically separated products and were supported by the identification of transient upstream BT biotransformation products, which included benzenethiols. Thiophenic acid products were also identified, and pathways that described BT biotransformation and novel HMM diaryl disulfide formation were constructed. This work shows that nondesulfurizing hydrocarbon-degrading organisms produce HMM diaryl disulfides from low molar mass polyaromatic sulfur heterocycles, and this may be taken into consideration when predicting the environmental fates of BT pollutants. [ABSTRACT FROM AUTHOR]

The key fragment element samarium (Sm) has a large neutron absorption cross section, which can hinder the absorption of neutrons by uranium and negatively affect the nuclear reaction. In order to realize the nuclear fuel cycle, the extraction of Sm was studied on the basis of electrolytic refining after the dry process. The electrochemical properties of SmCl3 and SnCl2 in LiCl-KCl molten system were systematically investigated by cyclic voltammetry (CV), square wave voltammetry (SWV), and open circuit potential (OCP). The diffusion coefficients of the Sn(II) and Sm(III) electrode processes were calculated to be 3.55–5.93 × 10−5 and 2.33–3.97 × 10−5 cm2 s−1, respectively. The co-reduction of Sm(III) and Sn(II) ions was studied. Sm was recycled by constant current electrolysis on the liquid Sn electrode, and the average extraction rate was about 94.23%. The samples were characterized and analyzed by X-ray diffraction analysis (XRD) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM), and the results showed that Sm extraction from liquid tin is feasible. [ABSTRACT FROM AUTHOR]

Soft ambient ionization sources generate reactive species that interact with analyte molecules to form intact molecular ions, which allows rapid, sensitive, and direct identification of the molecular mass. We used a dielectric barrier discharge ionization (DBDI) source with nitrogen at atmospheric pressure to detect alkylated aromatic hydrocarbon isomers (C8H10 or C9H12). Intact molecular ions [M]•+ were detected at 2.4 kVpp, but at increased voltage (3.4 kVpp), [M + N]+ ions were formed, which could be used to differentiate regioisomers by collision‐induced dissociation (CID). At 2.4 kVpp, alkylbenzene isomers with different alkyl‐substituents could be identified by additional product ions: ethylbenzene and ‐toluene formed [M‐2H]+, isopropylbenzene formed abundant [M‐H]+, and propylbenzene formed abundant C7H7+. At an operating voltage of 3.4 kVpp, fragmentation of [M + N]+ by CID led to neutral loss of HCN and CH3CN, which corresponded to steric hindrance for excited state N‐atoms approaching the aromatic ring (C‐H). The ratio of HCN to CH3N loss (interday relative standard deviation [RSD] < 20%) was distinct for ethylbenzene and ethyltoluene isomers. The greater the number of alkyl‐substituents (C‐CH3) and the more sterically hindered (meta > para > ortho) the aromatic core, the greater the loss of CH3CN relative to HCN was. [ABSTRACT FROM AUTHOR]

Cancer is a universal disease with a high mortality rate and caused by an uncontrolled growth of abnormal cells. Each cancer has its unique molecular change such as up/down-regulations of biological molecules in cancer cells. These biological molecules have been identified as biomarkers and used as a target analyte for cancer diagnosis. Since the level of cancer biomarkers is very insufficient at an early stage cancer, there is a need for technological advances that can be more accurate, ultra-sensitive, trustworthy, and selective to biomarkers. This review summarizes evaluation methods and recent advances in electrochemical and optical (fluorescent and colorimetric) biosensors to detect various cancer biomarkers as molecular targets. Electrochemical methods demonstrate rapid and ultra-sensitive detection of cancer biomarkers. And, fluorescent biosensors present improved target detection sensitivity by signal amplification strategy as well as provide the possibility to sense multiple biomarker targets with multiple fluorescent probes. Colorimetric biosensors easily and quickly detect cancer biomarkers by the naked eye for use as a point-of-care testing (POCT) platform. These biosensors can be further improved by understanding the complication of cancer cells and the molecular alterations in cancer progression for early diagnosis of cancer and patient prognosis. [ABSTRACT FROM AUTHOR]

Rationale: Trinitrotoluene (TNT) and its derivatives are found in the environment. Depending on the analysis conditions, TNT may be detected as a deprotonated molecule or a molecular ion through atmospheric pressure chemical ionization (APCI). Dichloromethane (CH2Cl2) is used as an extraction solvent for TNT from environmental samples and as an ionizing agent to generate chlorinated species. APCI mass spectra of TNT dissolved in CH2Cl2 revealed the presence of only the [TNT − H]− ion. This phenomenon was investigated by reactions with the CH2Cl2‐related reactant ions. Methods: TNT in CH2Cl2 was ionized through APCI, and CH2Cl2 and acetone were used as the eluent. The vaporizing temperature was varied from 200 to 350°C. TNT‐related ions and reactant ions were analyzed. Detection limits for TNT were determined under different conditions. Energy‐minimized structures of the product ions were used to interpret the analysis results. Results: Significant [TNT − H]− ion was observed, but the [TNT + Cl]− and TNT•− ions were not detected. The [HCl + Cl]− and [3acetone + Cl]− ions were detected as reactant ions when using CH2Cl2 and acetone as eluent, respectively. Other potential reactant ions such as CH2Cl2•− and [CH2Cl2 + Cl]− were not observed. The detection limit improved as the vaporizing temperature increased. The favorability of [TNT − H]− formation was explained on the basis of the heats of reactions. Conclusions: The [TNT − H]− ion was primarily produced by the deprotonation reaction between CH2Cl2•− and neutral TNT. This reaction was determined to be significantly exothermic. CH2Cl2 can be helpful for the analysis of TNT in environmental samples through APCI mass spectrometry. [ABSTRACT FROM AUTHOR]

In this research report, we prepared an electrochemical sensor based on the molecularly imprinted poly(p‐aminophenol) supported by silver nanoparticles capped with 2‐mercaptobenzoxazole for the selective and sensitive detection of endocrine disrupting 17‐β‐estradiol (E2). The electropolymerization of the functional monomer prepared the proposed molecularly imprinted polymer (MIP) composite‐based sensor in the presence of E2 as a template. The recognition materials were characterized using Fourier transform infrared, cyclic voltammetry (CV), square wave voltammetry (SWV), scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and X‐ray powder diffraction techniques. The electrochemical measurements were performed by employing both CV and SWV methods. We did the optimization of critical parameters affecting the sensor performances through the experimental design and verification. The developed sensor showed a linear range from 10 pM to 100 nM with the calculated quantification and detection limits of 1.86 and 6.19 pM, respectively. The incorporation of AgNP with high electrical conductivity into the MIP matrix enhanced the sensor's performance. Furthermore, the sensor was applied to determine E2 in real water samples without any sample preconcentration steps to achieve the percent recovery of 91.87% to 98.36% and acceptable reusability and storage stability performances. [ABSTRACT FROM AUTHOR]

Keywords: electrochemical reduction; kinetic parameter; rhenium; uranium EN electrochemical reduction kinetic parameter rhenium uranium 349 362 14 05/12/22 20220501 NES 220501 1 Introduction The key for the sustainable development of nuclear energy is to develop an efficient nuclear fuel cycle system. The analysis result of ESD indicates that the reduced uranium exists in the form of U(IV) ion rather than UO SB 2 sb , while rhenium in the form of rhenium oxide deposited on Mo electrode. Since U(IV) can be easily precipitated from aqueous solution, reduction of U(VI) into U(IV) has been regarded as an effective way to decontaminate uranium from radioactive waste [[13], [17]]. Evidently, the cyclic voltammogram of U(VI) provides us with a series of electrochemical reactions corresponding to redox behavior of U and the possibility for the reduction of uranium by direct electrolysis from hydrochloric acid. [Extracted from the article]

Correct assessment of the fatty acyl at the glycerol sn-2 position in triacylglycerol (TAG) analysis by liquid chromatography and mass spectrometry (LC-MS) is challenging. Ammonium hydroxide (NH4OH) is the preferred choice for the solvent additive for the formation of the ammonium adduct ([M + NH4]+). In this study, the influence of different NH4OH concentrations in the eluents on TAG adduct formation and fragmentation under LC-MS analysis was assessed. Increasing NH4OH concentrations delayed the chromatographic elution time according to a power function. The [M + NH4]+ and [M + ACN + NH4]+ adducts (where ACN means acetonitrile) were formed at all ammonium concentrations assayed. [M + ACN + NH4]+ predominated above 18.26 mM [NH4OH], and the intensity of [M + NH4]+ dropped. TAG fragmentation for fatty acyl release in the MSE was reduced with increasing [M + ACN + NH4]+ adduct, which suggests that ACN stabilizes the adduct in a way that inhibits the rupture of the ester bonds in TAGs. A linear equation (Hsn-I = a × H[M+NH4]+, where sn-I refers to the sn position of the glycerol (I = 1, 2, or 3) and H is the peak height) was deduced to quantify the dehydroxydiacylglycerol fragment intensity in relation to [M + NH4]+ intensity in the full scan. This equation had a slope mean value of 0.369 ± 0.058 for the sn-1 and sn-3 positions, and of 0.188 ± 0.007 for the sn-2 position. [ABSTRACT FROM AUTHOR]

Rationale: The development of an automated platform for the positional analysis of triglycerides (TAGs) based on electrospray ionization tandem mass spectrometry (ESI‐MS/MS) continues to be pursued. This work evaluates the positional sensitivities of the collision‐induced dissociation (CID) spectra of a representative set of XYZ triglycerides using sodium, lithium, and ammonium salts as complexing agents. Methods: A set of triglycerides were synthesized and analyzed via ESI‐MS/MS using an ion trap mass spectrometer. Using three different complexing agents, the product ion spectra of the corresponding precursor ions for twelve XYZ TAGs were collected, where X, Y, and Z represent C16:0, C18:1(c‐9), C18:2(cc‐9,12), and C20:4(cccc‐5,8,11,14) fatty acid chains. These data were then used to prepare ternary plots for four positional isomer systems to evaluate the positional sensitivity differences among the three different complexing agents. Results: The positional sensitivities for each of the four positional isomer systems were robust for the sodium and lithium adducts. The CID data for the sodium and lithium TAGs demonstrated an unfavorable loss of the fatty acid in the center position and showed a higher sensitivity to fatty acid position, when compared with the CID data for ammonium adducts, especially for the arachidonic acid containing triglycerides. Conclusions: The data shows that that the relative abundances of the DAG product ions for the XYZ‐type TAGs when using sodium and lithium complexing agent adducts are sensitive to fatty acid position and are consistent for the diverse array of TAGs studied in this work. This suggests that using sodium or lithium as the complexing agent may be advantageous for the development of an automated platform for the positional analysis of complex TAG mixtures based on ESI‐MS/MS. [ABSTRACT FROM AUTHOR]

Lipidomics is a research area that investigates lipidomes that refer to the complete lipid profile within a cell, tissue, organism, or ecosystem by focusing on the interactions with neighboring molecules at the inter- or intracellular spaces of organisms. In recent decades, lipidomics has greatly evolved along with developments in mass spectrometric analysis (i.e., ionization approaches, the types of analyzers, and the data processing tools), leading to a rapid and accurate performance in the identification and quantification of individual lipid species. In this contribution, the identification and quantification of triacylglycerol (TAG) and phospholipid (PL) species in marine sources using mass spectrometry analysis are comprehensively discussed along with their physiological roles and health-beneficial effects on the human body. Moreover, this review emphasizes the importance of the isotopic deconvolution and instrument responses caused by the difference in the carbon number and the unsaturation of TAG and PL species in quantitative analysis. Most TAG and PL detected in marine taxa possess a high proportion of polyunsaturated ω3 long-chain polyunsaturated fatty acids (LCPUFA, ≥C20) in particular eicosapentaenoic acid (EPA, 20:5ω3) and docosahexaenoic acid (DHA, 22:6ω3), indicating the large number and structural diversity of glycerolipid species containing EPA and DHA. This review also discusses the health effects of TAG and PL species esterified with ω3 LCPUFA. Given that most fisheries science and aquaculture research during recent decades has mainly focused on ω3 LCPUFA after release from parent molecules, discussion of the health effects of ω3 LCPUFA in the form of TAG and PL extends understanding of the bioactivities of ω3 fatty acids as they occur naturally. [ABSTRACT FROM AUTHOR]

In order to investigate the solvent effects on double-region atmospheric pressure chemical ionization-mass spectrometry (DRAPCI-MS) source, the differences in the ionization efficiency of 3-ethenylpyridine (3-EP) as an environmental tobacco smoke (ETS) marker were analyzed by using different standard solvents. These included cyclohexane, methanol, acetone and acetonitrile, and the reasons for causing those differences were studied and the performances of this method with the different standard solvents were compared. The results showed that: 1) The standard solvents affected the ionization efficiency of 3-EP, thereby influenced the limit of detection (LOD) and the limit of quantification (LOQ) of the method. By creating different solvent atmospheres, it was found that the differences in the ionization efficiency of 3-EP might be the results of the combined action of proton competition and cluster embedding of neutral molecules. On that basis, a DRAPCI-MS analysis method for 3-EP was developed by taking cyclohexane as the standard solvent. The LOD and LOQ of the developed method were 0.38 and 1.15 ng/L respectively. The calibration curve was obtained at a low concentration range with a satisfactory regression coefficient of 0.996 4. 2) The dynamic detection of 3-EP variations in ETS indicated that a suitable standard solvent could extend the time range of dynamic detection and well represented the characteristics of dynamic variation of ETS. It was necessary to consider the possible interference caused by the solvent effect and to optimize the ratio and dosage of the standard solvent when adopting atmospheric MS for quantitative analysis. [ABSTRACT FROM AUTHOR]

Supercritical fluid chromatography (SFC) in combination with mass spectrometry is a promising alternative to traditional chromatographic methods for the separation of polar nitrogen-containing compounds. The specificity of carbon dioxide-based mobile phases, used in this method, can affect the processes of the mass-spectrometric ionization of analytes and, as a consequence, the optimization strategy of the SFC–MS method. In this study, the effects of the composition of the CO2–methanol mobile phase, its flow rate, and also the parameters of the ion source (ESI capillary and corona discharge needle voltages, temperature) on the efficiency of ESI and APCI for a wide range of nitrogen-containing compounds from different classes were investigated. It was found that, because of the high basicity of the analytes under study, ESI in the positive ion mode is the preferred method of ionization, providing a multiple gain in efficiency compared to APCI for most analytes. An increase in the concentration of carbon dioxide in the mobile phase leads to a significant increase in the ESI efficiency and has a multidirectional effect on the ionization of analytes with different proton affinities under APCI conditions. An increase in APCI temperature leads to a decrease in the intensity of signals of protonated molecules and to the occurring of fragmentation processes regardless of the composition of the mobile phase for the vast majority of analytes. [ABSTRACT FROM AUTHOR]

There has been an increased interest in the development of green analytical methods for polycyclic aromatic hydrocarbons in environmental samples due to their toxicity and ubiquitous nature. In this work, the feasibility of on‐line supercritical fluid extraction‐supercritical fluid chromatography‐tandem mass spectrometry was investigated for rapid and automated determination of the 16 United States Environmental Protection Agency priority polycyclic aromatic hydrocarbons in particulate matter samples. Three specialty polycyclic aromatic hydrocarbons columns with different stationary phases were screened and an octadecyl‐silica column was selected for method development. Enhanced extraction efficiency was achieved using an extraction program with gradient flow rate and gradient concentration of acetonitrile as a modifier. The method was evaluated by analyzing standard reference materials of urban dust and diesel particulate matter from the National Institute of Standards and Technologies. Possible reasons for the unsatisfactory recoveries with certain polycyclic aromatic hydrocarbons are discussed. [ABSTRACT FROM AUTHOR]

An isotope pattern deconvolution (IPD) quantification method has been applied for the determination of five substances (amphetamine, benzoylecgonine, cocaine, methamphetamine and MDMA) in wastewater for the application in wastewater-based epidemiology (WBE). A previously validated method that used a calibration curve for quantification was modified to apply IPD. The two approaches were compared in terms of analytical uncertainty in recovery studies of quality control samples, i.e. six wastewater samples from different geographical origins spiked at two concentration levels. Both methods were reliable as they passed (z-score < 2) in an interlaboratory exercise. After 60 individual determinations, IPD provided 11 results outside recovery limits (70–120%) while the previous method produced 31 adverse results. All mean values for IPD were accurate whereas 6 out of 10 results showed RSD values higher than 30% or recoveries outside limits when using the former method. Moreover, the calculated method bias for the latter doubles that of IPD, which, in turn, makes the combined uncertainty (u(c)) much higher. Consequently, a simple change of data treatment—IPD quantification methodology—resulted in a lower uncertainty of the estimated illicit drug concentration, one of the main steps contributing to the final uncertainty in the normalized daily drug consumption through WBE. The current study demonstrated that the employment of IPD can also be very interesting for future applications of WBE, especially when matrix effects are high, complicating accurate quantification. In addition, when a high number of samples and/or compounds need to be analysed, IPD is faster than calibration and, eventually, cost-effective when isotopically labelled internal standard is highly expensive. [ABSTRACT FROM AUTHOR]

By the on-chip integration of a droplet generator in front of an emitter tip, droplets of non-polar solvents are generated in a free jet of an aqueous matrix. When an IR laser irradiates this free liquid jet consisting of water as the continuous phase and the non-polar solvent as the dispersed droplet phase, the solutes in the droplets are ionized. This ionization at atmospheric pressure enables the mass spectrometric analysis of non-polar compounds with the aid of a surrounding aqueous matrix that absorbs IR light. This works both for non-polar solvents such as n-heptane and for water non-miscible solvents like chloroform. In a proof of concept study, this approach is applied to monitor a photooxidation of N-phenyl-1,2,3,4-tetrahydroisoquinoline. [ABSTRACT FROM AUTHOR]

Rationale: The developments of new ionization technologies based on processes previously unknown to mass spectrometry (MS) have gained significant momentum. Herein we address the importance of understanding these unique ionization processes, demonstrate the new capabilities currently unmet by other methods, and outline their considerable analytical potential. Methods: The inlet and vacuum ionization methods of solvent‐assisted ionization (SAI), matrix‐assisted ionization (MAI), and laserspray ionization can be used with commercial and dedicated ion sources producing ions from atmospheric or vacuum conditions for analyses of a variety of materials including drugs, lipids, and proteins introduced from well plates, pipet tips and plate surfaces with and without a laser using solid or solvent matrices. Mass spectrometers from various vendors are employed. Results: Results are presented highlighting strengths relative to ionization methods of electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization. We demonstrate the utility of multi‐ionization platforms encompassing MAI, SAI, and ESI and enabling detection of what otherwise is missed, especially when directly analyzing mixtures. Unmatched robustness is achieved with dedicated vacuum MAI sources with mechanical introduction of the sample to the sub‐atmospheric pressure (vacuum MAI). Simplicity and use of a wide array of matrices are attained using a conduit (inlet ionization), preferably heated, with sample introduction from atmospheric pressure. Tissue, whole blood, urine (including mouse, chicken, and human origin), bacteria strains and chemical on‐probe reactions are analyzed directly and, especially in the case of vacuum ionization, without concern of carryover or instrument contamination. Conclusions: Examples are provided highlighting the exceptional analytical capabilities associated with the novel ionization processes in MS that reduce operational complexity while increasing speed and robustness, achieving mass spectra with low background for improved sensitivity, suggesting the potential of this simple ionization technology to drive MS into areas currently underserved, such as clinical and medical applications. [ABSTRACT FROM AUTHOR]

A capillary atmospheric pressure photoionization (cAPPI) source was used to analyze polycyclic aromatic hydrocarbons (PAHs) in complex matrices like grilled meat extract and urban dust reference material, as well as screening for PAHs in aqueous samples such as tap and lake water. A high‐throughput workflow was developed that allowed rapid screening of unknown samples by direct solid‐phase microextraction (SPME) coupled with cAPPI‐MS, with confirmatory gas chromatography performed only for samples containing trace amounts of PAHs. Extraction times were as low as 15 s, with a total analysis time of 2 min per sample for screening. Limits of detections were in the low pg/ml range and in the subpg/ml range for the direct and chromatographic approach, respectively, with a linear dynamic range between two and three orders of magnitude, as determined for 15 model PAHs. This rapid approach represents an attractive way to screen samples containing nonpolar compounds using an ambient ionization source. [ABSTRACT FROM AUTHOR]

Rationale: The anionic surfactants, among which are alkyl ether sulfates (AESs), are the most used class of surfactants in cleansing applications. The negatively charged head group of AESs is a sulfate moiety linked with a variable number of ethylene oxide units, i.e. a polyethylene glycol chain. The hydrophobic part of an AES is constituted by a linear alkyl chain of carbon atoms, generally obtained from natural fatty acids. Coconut oil fatty acids, including the sodium salts of coceth sulfate (CES) with chemical formula CxHy (OCH2CH2)nOSO3Na, are widely used as feedstock for AESs synthesis. CES is added to many cleaning products and detergents defined as non‐aggressive. Currently, no detailed structural information concerning the alkyl chain length x and, more importantly, the degree of ethoxylation n has been reported. Methods: A commercial standard solution of CES was characterized by tandem mass spectrometry, employing direct injection into the electrospray ionization (ESI) source of a a linear quadrupole ion trap mass spectrometer. Results: Two series of oligomeric species, characterized by a C12 and C14 alkyl chains, i.e. [C12H25(OCH2CH2)nOSO3]− and [C14H29(OCH2CH2)nOSO3]− with n ranging from 0 to 7, were successfully identified. The interpretation of these data was very useful for CES identification in three commercial dishwasher cleaning products. Conclusions: Direct injection MS/MS analysis of CES revealed a well‐defined molecular weight distribution and allowed the alkyl chain composition and the number of ethylene oxide units to be to identified. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A new capillary high‐performance liquid chromatography method with atmospheric pressure chemical ionization mass spectrometry was developed for the analysis of fatty acid methyl esters and long‐chain alcohols. The chromatographic separation was achieved using a Zorbax SB‐C18 HPLC column (0.3 × 150 mm, 3.5 μm) with a mobile phase composed of acetonitrile and formic acid and delivered isocratically at a flow rate of 10 μL/min. The column temperature was programmed simply, using a common column oven. Good reproducibility of the temperature profile and retention times were achieved. The temperature programming during the isocratic high‐performance liquid chromatography run had a similar effect as a solvent gradient; it reduced retention times of later eluting analytes and improved their detection limits. Two atmospheric pressure chemical ionization sources of the mass spectrometry detector were compared: an enclosed conventional ion source and an in‐house made ion source with a glass microchip nebulizer. The enclosed source provided better detectability of saturated fatty acid methyl esters and made it possible to determine the double bond positions using acetonitrile‐related adducts, while the open chip‐based source provided better analytical figures of merit for unsaturated fatty acid methyl esters. Temperature‐programmed capillary high‐performance liquid chromatography is a promising method for analyzing neutral lipids in lipidomics and other applications. [ABSTRACT FROM AUTHOR]

Rationale Hyphenation of atmospheric pressure chemical ionization (APCI) mass spectrometry with capillary and micro high‐performance liquid chromatography (HPLC) is attractive for many applications, but reliable ion sources dedicated to these conditions are still missing. There are a number of aspects to consider when designing such an ion source, including the susceptibility of the ionization processes to ambient conditions. Here we discuss the importance of ion source housing for APCI at low flow rates. Methods Selected compounds dissolved in various solvents were used to study ionization reactions at 10 μL/min flow rate. APCI spectra were generated using the Ion Max‐S source (Thermo Fisher Scientific) operated with or without the ion source housing. Results The APCI spectra of most compounds measured in the open and enclosed ion sources were markedly different. The differences were explained by water and oxygen molecules that entered the plasma region of the open ion source. Water tended to suppress charge transfer processes while oxygen diminished electron capture reactions and prevented the formation of acetonitrile‐related radical cations useful for localizing double bonds in lipids. The effects associated with the ion source housing were significantly less important for compounds that are easy to protonate or deprotonate. Conclusions The use of ion source housing prevented alternative ionization channels leading to unwanted or unexpected ions. Compared with the conventional flow rate mode (1 mL/min), the effects of ambient air components were significantly higher at 10 μL/min, emphasizing the need for ion source housing in APCI sources dedicated to low flow rates. [ABSTRACT FROM AUTHOR]

Rationale: Characterization of complex samples remains a challenging task due to the high number of compounds present. Matrix effects, ion discrimination and suppression are limiting factors which force the use of different methods for the same sample to gain a broad understanding of complex mixtures. Methods: Various ionization techniques such as electrospray ionization (ESI), atmospheric pressure photoionization (APPI) and atmospheric pressure chemical ionization (APCI) have been used in various problems for complex mixture analysis. Especially demanding is the analysis of energy‐related hydrocarbon mixtures, such as crude oil. Here, the different ionization sources alone and in combination with each other have been used on an ultrahigh resolution Orbitrap mass spectrometer to study a light crude oil. Results: Despite the great variety of the available ionization sources, there is no single technique which can fully characterize the crude oil. Each ionization technique shows a selectivity towards specific types of compounds. While ESI is the method of choice for the detection of polar compounds, APPI and APCI favor the detection of nonpolar and low‐to‐medium polar compounds, respectively. The combination of ESI/APPI favors hydrocarbons and oxygen‐containing species. Conclusions: Combining different ionization methods can be used as an alternative in order to gain more information about compounds present in a complex mixture although a combination of different ion sources could enhance suppression effects. [ABSTRACT FROM AUTHOR]

Seeds of papaya fruit (Carica papaya) are usually unused for the industry, but they have been previously reported to be anthelmintic. However, the effects and mechanisms involved in papaya seeds against root-knot nematodes (RKN) are poorly studied in soil incorporation. Here, we investigated soil biofumigation with papaya seeds against the RKN Meloidogyne incognita and the effect of their volatile organic compounds (VOCs) separately from non-VOCs. Soil biofumigation reduced the number of galls and eggs of RKN about 100% in tomato roots, by using seeds macerates at 4.0 g 100 mL−1, which is a feasible amount for field applications. The VOCs emitted by the seeds killed 80% of M. incognita second-stage juveniles after a few hours of exposure. Furthermore, the whole volatilome of the papaya seed was identified by gas chromatography. Some of the compounds have already been studied against RKN. Therefore, we examined the efficacy of all nonstudied compounds against M. incognita. The most promising compounds were vinyl acetate, phenylacetaldehyde and benzylacetonitrile with lethal concentrations (LC50) of 61.5, 101.3 and 14.4 μg mL−1, respectively. When vinyl acetate and phenylacetaldehyde were applied to the soil at the recommended commercial nematicide dose (396 μg mL−1), the effect on M. incognita was better than the commercial nematicide (Carbofuran), reducing 70% of the number of galls and eggs. However, benzylacetonitrile reduced galls and eggs only by 25%. These results provide evidence for biofumigation with papaya seeds as a sustainable approach to control RKN and the potential use of their VOCs as nematicidal compounds. [ABSTRACT FROM AUTHOR]