Search Results (47)

For the evaluation of the chemical composition of Inula hookeri f. major Ling, ultra-high-performance liquid chromatography quadrupole-Exactive Orbitrap mass spectrometry (UHPLC-Q-Exactive-Orbitrap MS) was integrated with feature-based molecular networking (FBMN) and SIRIUS. The chromatographic separation of the chemical components from Inula hookeri f. major Ling was conducted on a Hypersil GOLD™ aQ C₁₈ (100 mm × 2.1 mm, 1.9 μm) using gradient elution, with a 0.1% formic acid aqueous solution and acetonitrile as the mobile phase. Mass spectrometric analysis was performed in both positive and negative ion modes using an electrospray ionization (ESI) source. Based on the obtained high-resolution fragment ions, FBMN was conducted to enable the clustering and visualization of structurally similar compounds. Molecular formulas were predicted and MS/MS fragment ions were interpreted with the assistance of SIRIUS. A total of 162 compounds were tentatively annotated from Inula hookeri f. major Ling, including terpenoids, phenylpropanoids, fatty acids, organic acids, and other types of compounds. The application of the strategy incorporating UHPLC-Q-Exactive-Orbitrap MS, FBMN, and SIRIUS enables the systematic characterization of the chemical composition of Inula hookeri f. major Ling. Full article

Electrohydrodynamic effects can significantly alter transport processes in reacting flows, even when the plasma is weakly ionized. However, predictive modeling of such plasma–flame interactions remains challenging due to the multiscale coupling among charge transport, fluid motion, and chemical kinetics. This study presents a charge-transport closure model to investigate electrohydrodynamic influences on laminar non-premixed flames. A two-dimensional computational framework in cylindrical coordinates is used to simulate plasma-assisted methane–air diffusion flames under weak electric-field conditions representative of practical combustion environments. To represent plasma–flow coupling in a computationally feasible yet physically consistent manner, a charge-transport formulation based on the drift–diffusion approximation is employed. The model solves transport equations for representative positive and negative charge carriers coupled with Poisson’s equation for the electric potential to obtain a self-consistent electric field. This formulation assumes a weakly ionized regime for low-temperature plasma-assisted combustion, in which neutral species dominate the mass and momentum transport, while ionization chemistry is simplified and charge transport primarily influences the flow through electrohydrodynamic body forces and Joule heating. Assuming a weak electric field, the steady flamelet model is applied, in which plasma effects primarily influence scalar transport and local thermal balance rather than inducing significant bulk ionization dynamics. The governing equations are discretized using a high-order compact finite-difference scheme that provides improved resolution of steep gradients in temperature, species concentration, and space-charge density near thin reaction zones. The canonical laminar flame model configuration was validated using the established laminar methane–air diffusion flame benchmark, and steady-state spatial profiles of key transport properties were evaluated. Two-dimensional analysis identified the discharge coupling location as an important factor. The application of discharge in the fuel-air mixing region leads to a clear restructuring of the flame. When the discharge is activated, electrohydrodynamic forcing and ion-driven momentum transfer produce a highly localized, columnar flame with sharp gradients and a confined reaction zone. Compared with the baseline case, the plasma-assisted flame localizes the OH-rich reaction zone, confines the high-temperature region into a narrow column, and enhances downstream H₂O formation. Full article

The detection of plastic explosives in vapor form is extremely challenging due to the very low volatility of their primary components, such as RDX and PETN. To overcome this limitation, volatile chemical markers like 2,3-dimethyl-2,3-dinitrobutane (DMNB) are added to explosive formulations to enable indirect vapor detection. This study presents a rapid method for detecting and quantifying DMNB vapors using a handheld ion mobility spectrometer (IMS) operating near ambient temperature, ammonia-doped and equipped with a non-radioactive corona discharge ionization source. The instrument, model LCD-3.2E (Smiths Detection Ltd.), is based on a twin drift–cell time-of-flight configuration and simultaneously records ion mobility spectra in both positive and negative modes. DMNB generated distinct product ion peaks in both modes, with reduced mobility values (K₀) of 1.42 cm²V⁻¹s⁻¹ (positive) and 1.37 cm²V⁻¹s⁻¹ (negative). The method demonstrated high sensitivity, with limits of detection calculated at 1.4 ppb_v (10.2 × 10⁻³ mg m⁻³) in positive mode and 3.1 ppb_v (22.7 × 10⁻³ mg m⁻³) in negative mode. The IMS system provided rapid responses within seconds and covered a quantifiable concentration range of 5–3000 ppb_v, with saturation estimated to appear above approximately 5 ppm_v (36.6 mg m⁻³). The simultaneous dual-polarity response of the DT IMS enhances both the selectivity and reliability of identification. These findings confirm the capability of portable IMSs for fast trace vapor detection in DMNB, supporting its application in field-based screening scenarios such as luggage inspection or container interrogation, where indirect detection of plastic explosives is required. Full article

Rearrangements such as the McLafferty rearrangement are common in mass spectrometry of positive ions, but rare in negative ions. The present article searched the literature for McLafferty rearrangements of negative ions formed by negative electrospray ionization (-ESI) or by negative-ion chemical ionization (NICI). McLafferty Rearrangements have been reported for negative ions formed by -ESI, yet not for anions formed by NICI in GC-MS and GC-MS/MS. This article reports for the first time a McLafferty Rearrangement of the collision-induced dissociation (CID) of precursor ions due to [M−PFB]⁻ generated by NICI in the GC-MS/MS analysis of pentafluorobenzyl (PFB) esters and thioesters of diethyl phosphates (CH₃CH₂O)₂PO₂, diethyl thiophosphates (CH₃CH₂O)₂PSO, and diethyl dithiophosphates (CH₃CH₂O)₂PS₂. Two specific product anions due to α,β-cleavages and formation of neutral losses of ethene and ethanol are formed. No McLafferty rearrangements were observed in the CID of 1-chloropropyl derivatives of these dialkyl organophosphates in the positive-ion chemical ionization (PICI) mode. McLafferty rearrangements of PFB esters of organophosphates have been observed in the EI mode. No McLafferty rearrangements were observed in the EI and NICI of diethyl fluoro phosphate, a representative of dialkyl fluoro phosphates. McLafferty rearrangements of negative ions seem to be more common than assumed so far. Full article

Paper spray ionization mass spectrometry (PSI-MS) enables rapid analysis with minimal sample preparation, yet negative-ion mode performance has been limited by poor sensitivity and unstable signals, similar to conventional electrospray ionization. In this study, we optimized negative PSI tandem MS (MS/MS) for twelve endocrine-disrupting chemicals (EDCs) and related biomarkers—including bisphenols, phthalates, parabens, and substituted phenols—used as model analytes. A systematic solvent and additive screen identified 1 mM ammonium fluoride in methanol and 0.1% ammonium hydroxide in 9:1 MeOH/carbon tetrachloride as optimal conditions, providing enhanced deprotonated-ion intensities and improved stability. Calibration curves generated under these conditions showed excellent linearity, with limits of quantitation (LOQs) in the low-ppb range. Application to cosmetic formulations demonstrated reliable paraben quantitation. In fortified hand cream, LOQs below 1 mg/kg were achieved, with recoveries of 93–110% and intra- and inter-day precision below 10% RSD. Notably, PSI-MS/MS performance was comparable to LC–MS/MS, without a separation step. These results demonstrate the feasibility of optimized negative PSI-MS as a sensitive and robust tool for paraben determination in cosmetics and highlight its potential as a versatile platform for broader EDC quantification. Full article

Arachidonic acid (eicosatetraenoic acid) is the precursor of the eicosanoids, which include prostaglandins (PG). Methods based on GC-MS/MS are the Gold Standard for the quantitative analysis of eicosanoids in biological samples. After extraction and derivatization, biological F₂-prostaglandins are analyzed on quadrupole GC-MS/MS apparatus as pentafluorobenzyl (PFB) ester trimethylsilyl (TMS) ether derivatives, i.e., PFB-TMS. Negative-ion chemical ionization (NICI) in the ion source generates abundant anions due to [M-PFB]⁻, which are detected in the selected ion monitoring (SIM) mode. Collision-induced dissociation (CID) of [M-PFB]⁻ in the collision cell generates numerous product ions, which are suitable candidates for quantitative analyses in the selected reaction monitoring (SRM) mode. In this article, we report on investigations of gas-phase reactions of PFB-TMS derivatives of F₂-prostaglandins, which consist of PGF_2α, 8-iso-PGF_2α, and up to 62 further isomers, known as the F₂-isoprostanes. We performed a meta-analysis of previously reported CID mass spectra (32 eV) of PFB-(TMS)₃ of seven chemically closely related isomeric F₂-prostaglandins of the 15-F_2t-IsoP type. This unique dataset contains 19 product ions generated by CID of the common precursor at m/z 569 [M-PFB]⁻ in the m/z range of 150–600. All isomers produced the same product ions, which, however, greatly differed in their intensity. Principal Component Analysis (PCA) and Receiver Operating Characteristic (ROC) Analysis (ROCA) were performed. Two compounds, i.e., 8-iso-9β,11α-PGF_2α and 9α,11β-PGF_2α, and two product ions, i.e., m/z 299 [M-PFB-3×TMSOH]⁻ and m/z 215 [M-PFB-3×TMSOH-C₄H₈-C₂H₄]⁻, were noticeable. ROCA revealed the highest disagreement between PGF_2α and 8-iso-9β,11α-PGF_2α (AUC = 0.7075 ± 0.0834, p = 0.0248). PCA and ROCA are of limited value in the GC-MS/MS of closely chemically related F₂-prostaglandins. Fragmentation mechanisms were proposed for the formation of all 19 product ions generated by CID of common precursor anions due to [M-PFB]⁻. Full article

Structural characterization of natural products in complex herbal extracts remains a major challenge in phytochemical analysis. In this study, we present a novel post-acquisition data-processing strategy—key ion diagnostics–neutral loss filtering (KID-NLF)—combined with ultra-high-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MS) for systematic profiling of the medicinal plant Terminalia chebula. The strategy consists of four main steps. First, untargeted data are acquired in negative electrospray ionization (ESI⁻) mode. Second, a genus-specific diagnostic ion database is constructed by leveraging characteristic fragment ions (e.g., gallic acid, chebuloyl, and HHDP groups) and conserved substructures. Third, MS/MS data are high-resolution filtered using key ion diagnostics and neutral loss patterns (302 Da for HHDP; 320 Da for chebuloyl). Finally, structures are elucidated via detailed spectral analysis. The methanol extract of T. chebula was separated on a C18 column using a gradient of acetonitrile and 0.1% aqueous formic acid within 33 min. This separation enabled detection of 164 compounds, of which 47 were reported for the first time. Based on fragmentation pathways and diagnostic ions (e.g., m/z 169 for gallic acid, m/z 301 for ellagic acid, and neutral losses of 152, 302, and 320 Da), the compounds were classified into three major groups: gallic acid derivatives, ellagitannins (containing HHDP, chebuloyl, or neochebuloyl moieties), and triterpenoid glycosides. KID-NLF overcomes key limitations of conventional workflows—namely, isomer discrimination and detection of low-abundance compounds—by exploiting genus-specific structural signatures. This strategy demonstrates high efficiency in resolving complex polyphenolic and triterpenoid profiles and enables rapid annotation of both known and novel metabolites. This study highlights KID-NLF as a robust framework for phytochemical analysis in species with high chemical complexity. It also paves the way for applications in quality control, drug discovery, and mechanistic studies of medicinal plants. Full article

Background/Objectives: Oxazolidinones are novel antimicrobial agents used to combat bacterial infections, particularly multidrug-resistant strains. However, the synthesis of oxazolidinone derivatives, such as linezolid, often involves the use of 3,4-difluoronitrobenzene (DFNB) as an initiator. Despite its effectiveness, residual DFNB in drug products raises significant health concerns due to its structural similarity to toxic and carcinogenic nitrobenzenes. This contamination is particularly concerning in pharmaceutical formulations, where it poses potential patient safety hazards. Therefore, strict concentration limits for this impurity are necessary. Methods: To ensure tight control of DFNB concentrations, this study established an 8.3 µg/g target limit. An advanced high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to overcome current limitations in detecting trace DFNB. Under negative atmospheric pressure chemical ionization (APCI) conditions, DFNB exhibited characteristic ion formations, including [M]^•− through electron capture and [M − F + O]⁻ via substitution reactions. The quantitative method utilizes MS/MS ion transitions of the substitution product while optimizing chromatographic and spectrometric parameters to enhance both sensitivity and specificity. Conclusions: Validation tests confirm the efficiency, precision, and accuracy of this method, with a low limit of quantification (LOQ) of 5 ng/mL (0.83 µg/g). This technique enables accurate detection and quantification of DFNB in linezolid active pharmaceutical ingredient (API) and various formulations, providing a reliable tool for quality control. This method ensures the safe use of linezolid by effectively monitoring and minimizing the risks associated with DFNB contamination. Full article

Mass spectrometry (MS) is a highly selective and sensitive analytical tool with a myriad of applications, but such techniques are typically used in laboratory settings due to the handling and preparations that are necessary. The merging of two streams of robust research, portable MS systems and next-generation ambient ionization methods, now provides the ability to perform high-performance chemical screening in an on-site and on-demand manner, with natural applications in disciplines such as forensic science, where samples of interest are typically found in field environments (i.e., traffic stops, crime scenes, etc.). Correspondingly, investigations regarding the suitability and robustness of these methodologies when they are utilized for authentic forensic evidence processing are prudent. This work reports critical insights into the role that choice of spray solvent system plays regarding analytical performance of two spray-based ambient ionization sources, paper spray ionization (PSI) and filter cone spray ionization (FCSI), when employed for evidence types containing emerging synthetic cannabinoids. The systematic characterization studies reported herein show that the applied spray solvent can dramatically affect both spectral intensity and signal duration, and in some circumstances, yield deleterious false negative responses. Overall, acetonitrile-based systems are shown to strike a balance between analyte solubility concerns and spray ionization dynamics of the novel ion sources employed on portable MS systems. Full article

Patulin, a toxic mycotoxin, can contaminate apple-derived products. The FDA has established an action level of 50 ppb (ng/g) for patulin in apple juice and apple juice products. To effectively monitor this mycotoxin, there is a need for adequate analytical methods that can reliably and efficiently determine patulin levels. In this work, we developed an automated sample preparation workflow followed by liquid chromatography–atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS/MS) detection to identify and quantify patulin in a single method, further expanding testing capabilities for monitoring patulin in foods compared to traditional optical methods. Using a robotic sample preparation system, apple juice, apple cider, apple puree, apple-based baby food, applesauce, fruit rolls, and fruit jam were fortified with ¹³C-patulin and extracted using dichloromethane (DCM) without human intervention, followed by an LC-APCI-MS/MS analysis in negative ionization mode. The method achieved a limit of quantification of 4.0 ng/g and linearity ranging from 2 to 1000 ng/mL (r² > 0.99). Quantitation was performed with isotope dilution using ¹³C-patulin as an internal standard and solvent calibration standards. Average recoveries (relative standard deviations, RSD%) in seven spike matrices were 95% (9%) at 10 ng/g, 110% (5%) at 50 ng/g, 101% (7%) at 200 ng/g, and 104% (4%) at 1000 ng/g (n = 28). The ranges of within-matrix and between-matrix variability (RSD) were 3–8% and 4–9%, respectively. In incurred samples, the identity of patulin was further confirmed with a comparison of the information-dependent acquisition-enhanced product ion (IDA-EPI) MS/MS spectra to a reference standard. The metrological traceability of the patulin measurements in an incurred apple cider (21.1 ± 8.0 µg/g) and apple juice concentrate (56.6 ± 15.6 µg/g) was established using a certified reference material and calibration data to demonstrate data confidence intervals (k = 2, 95% confidence interval). Full article

Hot spring (HS) waters manifest diverse positive effects on the skin due to their unique chemical compositions. Sodium hyaluronate acid (HA) comprises N-acetylglucosamine and D-glucuronic acid, and distinguishes itself with superior qualities in skin regeneration, providing moisturizing and anti-aging benefits. The combination of HA with HS water is widely applied across ophthalmology, pneumology, nutrition, and cosmetics. This study delved into the application of HA in cosmetology, with a focus on its interaction with HS water and its effects on moisture retention and promoting wound healing. In particular, with the alkaline pH levels of the Yumoto HS, HA molecules may undergo dissociation to be ionized resulting in a negatively charged polymer and interacting with positively charged ions in the HS water through electrostatic interactions. The shifted peaks in the FTIR result and zeta potential shifts to a less negative region in the case of HA-HS compared to HA-DI indicate an ionic interaction between HS water and HA. Moisture tests confirmed the sustained hydration when HA is dissolved in HS water, underscoring its potential to improve skin hydration at certain concentrations, specifically at 0.5% and 1%. Additionally, MTT assay results demonstrated that HS water stimulates the growth of fibroblast cells compared to distilled water, implying its potential beneficial effect in wound healing. These findings suggested the multifaceted benefits of HAHS in skincare, highlighting its role in enhancing skin hydration and potentially accelerating wound healing processes, thus presenting avenues for the development of advanced cosmeceutical formulations. Full article

Oil sands process-affected water (OSPW) contains a diverse mixture of inorganic and organic compounds. Naphthenic acids (NAs) are a subset of the organic naphthenic acid fraction compounds (NAFCs) and are a major contributor of toxicity to aquatic species. Thousands of unique chemical formulae are measured in OSPW by accurate mass spectrometry and high-resolution mass spectrometry (MS) analysis of NAFCs. As no commercial reference standard is available to cover the range of compounds present in NAFCs, quantitation may best be referred to as “semi-quantitative” and is based on the responses of one or more model compounds. Negative mode electrospray ionization (ESI-) is often used for NAFC measurement but is prone to ion suppression in complex matrices. This review discusses aspects of off-line sample preparation techniques and liquid chromatography (LC) separations to help reduce ion suppression effects and improve the comparability of both inter-laboratory and intra-laboratory results. Alternative approaches to the analytical parameters discussed include extraction solvents, salt content of samples, extraction pH, off-line sample cleanup, on-line LC chromatography, calibration standards, MS ionization modes, NAFC compound classes, MS mass resolution, and the use of internal standards. Full article

(1) Background: Plant growth regulators (PGRs) can accelerate growth or improve the quality and quantity of bean sprouts but are forbidden to use in bean sprout cultivation, as the sprouting process’s increased chemicals will disturb the PGRs analysis. This article aimed to increase the accuracy and level of sensitivity of the LC-MS/MS method for the simultaneous analysis of 10 PGRs after mixed solid phase extraction (SPE) purification. (2) Methods: An LC-MS/MS detection method for 10 kinds of PGRs was established based on ESI ionization in the positive ion mode for 6-furfurylaminopurine (6-KT), paclobutrazol (PBZ), indole-2-acetic acid (IAA), and indole-3-butyric acid (IBA) and in the negative ion mode for gibberellin A3 (GA₃), 2,4-dichlorophenoxy acetic acid (2,4-D), 4-chlorophenoxyacetic acid (4-CPA), forchlorfenuron (FCF), thidiazuron (TDZ), and 6-benzyl adenine (6-BA). (3) Results: The 10 PGR compounds were detected within a concentration range of 1.0–50 ng/mL. The average recovery was 68.3–97.3% with relative standard deviations (RSD) of 4.6–15.2% (n = 6); the limit of detection (LOD) and limit of quantification (LOQ) were found to be 2 and 5 ng/g, respectively. PGRs were surveyed in 36 soybean sprouts and 33 mungbean sprouts; the results showed that 4-CPA and IAA were detected in 10 soybean sprouts and 10 mungbean sprouts, respectively. Five samples contained both 4-CPA and IAA. (4) Conclusions: The established method is simple, rapid, accurate, and highly sensitive for the detection of PGR residues in bean sprout products. Full article

Cu₂Se is a promising thermoelectric (TE) material due to its low cost, Earth abundance, and high thermoelectric properties. However, the biggest problem of Cu₂Se is its unstable chemical properties. In particular, under the action of an electric field or gradient temperature field, the chemical potential of copper ions inside the material increases. When the external field is strong enough, the chemical potential of copper ions at the negative end of the material reaches the chemical potential of elemental copper. Under these conditions, copper ions must precipitate out, causing Cu₂Se to be unstable, and making it unsuitable for use in applications. In this study, we prepared Cu_2−xMn_xSe (x = 0, 0.02, 0.04 and 0.06) series bulk materials by vacuum melting–annealing and sintered by spark plasma sintering (SPS). We investigated the effects of Mn doping on the composition, microstructure, band structure, scattering mechanism, thermoelectric properties, and stability of Cu₂Se. The results show that Mn doping can adjust the carrier concentration, promote the stabilization of the β-phase structure and improve the electrical properties of Cu₂Se. When x = 0.06, the highest power factor (PF) value of Cu_1.94Mn_0.06Se at 873 K was 1.62 mW m⁻¹ K⁻². The results of carrier scattering mechanism analysis based on the conductivity ratio method show that the sample doped with Mn and pure Cu₂Se had the characteristics of ionization impurity scattering, and the scattering factor was 3/2. However, the deterioration in thermal conductivity was large, and a superior zT value needs to be obtained. The cyclic test results of high-temperature thermoelectric properties show that Mn doping can hinder Cu⁺ migration and improve its thermoelectric stability, which preliminarily verifies the feasibility of using the stable zirconia mechanism to improve the thermoelectric stability of Cu₂Se. Full article

Opposing evidence exists for the source of the hydrogen ions (H⁺) during ketoacidosis. Organic and computational chemistry using dissociation constants and alpha equations for all pertinent ionizable metabolites were used to (1) document the atomic changes in the chemical reactions of ketogenesis and ketolysis and (2) identify the sources and quantify added fractional (~) H⁺ exchange (~H⁺e). All computations were performed for pH conditions spanning from 6.0 to 7.6. Summation of the ~H⁺e for given pH conditions for all substrates and products of each reaction of ketogenesis and ketolysis resulted in net reaction and pathway ~H⁺e coefficients, where negative revealed ~H⁺ release and positive revealed ~H⁺ uptake. Results revealed that for the liver (pH = 7.0), the net ~H⁺e for the reactions of ketogenesis ending in each of acetoacetate (AcAc), β-hydroxybutyrate (β-HB), and acetone were −0.9990, 0.0026, and 0.0000, respectively. During ketogenesis, ~H⁺ release was only evident for HMG CoA production, which is caused by hydrolysis and not ~H⁺ dissociation. Nevertheless, there is a net ~H⁺ release during ketogenesis, though this diminishes with greater proportionality of acetone production. For reactions of ketolysis in muscle (pH = 7.1) and brain (pH = 7.2), net ~H⁺ coefficients for β-HB and AcAc oxidation were −0.9649 and 0.0363 (muscle), and −0.9719 and 0.0291 (brain), respectively. The larger ~H⁺ release values for β-HB oxidation result from covalent ~H⁺ release during the oxidation–reduction. For combined ketogenesis and ketolysis, which would be the metabolic condition in vivo, the net ~H⁺ coefficient depends once again on the proportionality of the final ketone body product. For ketone body production in the liver, transference to blood, and oxidation in the brain and muscle for a ratio of 0.6:0.2:0.2 for β-HB:AcAc:acetone, the net ~H⁺e coefficients for liver ketogenesis, blood transfer, brain ketolysis, and net total (ketosis) equate to −0.1983, −0.0003, −0.2872, and −0.4858, respectively. The traditional theory of ketone bodies being metabolic acids causing systemic acidosis is incorrect. Summation of ketogenesis and ketolysis yield H⁺ coefficients that differ depending on the proportionality of ketone body production, though, in general, there is a small net H⁺ release during ketosis. Products formed during ketogenesis (HMG-CoA, acetoacetate, β-hydroxybutyrate) are created as negatively charged bases, not acids, and the final ketone body, acetone, does not have pH-dependent ionizable groups. Proton release or uptake during ketogenesis and ketolysis are predominantly caused by covalent modification, not acid dissociation/association. Ketosis (ketogenesis and ketolysis) results in a net fractional H⁺ release. The extent of this release is dependent on the final proportionality between acetoacetate, β-hydroxybutyrate, and acetone. Full article