Analysis In Real Time Ionization Research Articles

Molecular Insights into Gas-Particle Partitioning and Viscosity of Atmospheric Brown Carbon.

Biomass burning organic aerosol (BBOA), containing brown carbon chromophores, plays a critical role in atmospheric chemistry and climate forcing. However, the effects of evaporation on BBOA volatility and viscosity under different environmental conditions remain poorly understood. This study focuses on the molecular characterization of laboratory-generated BBOA proxies from wood pyrolysis emissions. The initial mixture, "pyrolysis oil (PO1)", was progressively evaporated to produce more concentrated mixtures (PO1.33, PO2, and PO3) with volume reduction factors of 1.33, 2, and 3, respectively. Chemical speciation and volatility were investigated using temperature-programmed desorption combined with direct analysis in real-time ionization and high-resolution mass spectrometry (TPD-DART-HRMS). This novel approach quantified saturation vapor pressures and enthalpies of individual species, enabling the construction of volatility basis set distributions and the quantification of gas-particle partitioning. Viscosity estimates, validated by poke-flow experiments, showed a significant increase with evaporation, slowing particle-phase diffusion and extending equilibration times. These findings suggest that highly viscous tar ball particles in aged biomass burning emissions form as semivolatile components evaporate. The study highlights the importance of evaporation processes in shaping BBOA properties, underscoring the need to incorporate these factors into atmospheric models for better predictions of BBOA aging and its environmental impact.

High-throughput DART-MS/MS for quantification of carboxymethyl lysine and carboxyethyl lysine in beef

Carboxymethyl lysine (CML) and carboxyethyl lysine (CEL), commonly found in heat-processed foods, pose considerable health risks. Conventional detection methods for these compounds are often slow and inefficient. This study presents a high-throughput and effective method utilizing Direct Analysis in Real-Time ionization coupled with triple quadrupole tandem mass spectrometry (DART-MS/MS) for quantifying CML and CEL in beef. The method demonstrated strong linearity between concentration and peak area across a range of 1–50 μg/mL, with detection and quantification limits of 0.15 μg/g and 0.6 μg/g, respectively. Remarkably, it enables the analysis of eight samples in just two minutes per run. Additionally, the use of buckwheat extract as an antioxidant during yak beef cooking resulted in a 7.72 % reduction in CML and a 1.46 % reduction in CEL. This study provides a robust and rapid method for detecting CML and CEL in food products, contributing to the improvement of food safety.

Interlaboratory and cross-platform accessibility of time-of-flight wood identification database

The mass spectral database of tree species built by US Fish and Wildlife Service has thousands of entries and has been a valuable resource to combat illegal logging and international trade. The database was and continues to be constructed using a particular ambient ionization time-of-flight mass spectrometry (TOF-MS) platform in the agency branch in Ashland, OR, with which queries of unknown wood samples are investigated exclusively. Laboratories that operate different MS instruments also have an interest in using the database if they can produce valid matches to known samples compatible with the database. Four species were selected for inter-laboratory comparison using Orbitrap MS instruments and the equivalent TOF-MS platform with direct analysis in real time ionization of institution-sourced wood samples. Identities of the known samples were confirmed by examination of their microscopic wood anatomy. Orbitrap analysis was able to identify each species as confidently as the TOF instruments, often with less variation in spectra but not necessarily greater mass accuracy or better-matched signal abundance to the control database. The Orbitrap program also had to be doubled to two scanned mass ranges appended for greater peak intensity, before spectra could be correctly matched to the database, but the program was successful.

Wood from Hardwood Angiosperms and Coniferous Gymnosperms Shows Distinctive Lignin Peaks in Direct Analysis in Real Time (DART) Mass Spectra.

A data set was constructed consisting of 3021 mass spectra randomly selected from all available families in the ForeST© (Forensic Spectra of Trees) database of mass spectra for wood analyzed by Direct Analysis in Real Time ionization coupled with time-of-flight mass spectrometry (DART-TOFMS). Clear and reproducible differences were observed between the lignin peaks for hardwood angiosperms and coniferous gymnosperms, with DART-TOFMS spectra of angiosperms showing significantly higher relative abundances for peaks associated with syringyl subunits. Application of the method to processed wood samples demonstrated that these differences can be used to provide support for enforcing trade laws by accurately identifying the source of finished wood products from hardwood angiosperms and coniferous gymnosperms.

Machine Learning-Based Species Classification Methods Using DART-TOF-MS Data for Five Coniferous Wood Species

Various problems worldwide are caused by illegal production and distribution of timber, such as deception about timber species and origin and illegal logging. Numerous studies on wood tracking are being conducted around the world to demonstrate the legitimacy of timber. Tree species identification is the most basic element of wood tracking research because the quality of wood varies greatly from species to species and is consistent with the botanical origin of commercially distributed wood. Although many recent studies have combined machine learning-based classification methods with various analytical methods to identify tree species, it is unclear which classification model is most effective. The purpose of this work is to examine and compare the performance of three supervised machine learning classification models, support vector machine (SVM), random forest (RF), and artificial neural network (ANN), in identifying five conifer species and propose an optimal model. Using direct analysis in real-time ionization combined with time-of-flight mass spectrometry (DART-TOF-MS), metabolic fingerprints of 250 individual specimens representing five species were collected three times. When the machine learning models were applied to classify the wood species, ANN outperformed SVM and RF. All three models showed 100% prediction accuracy for genus classification. For species classification, the ANN model had the highest prediction accuracy of 98.22%. The RF model had an accuracy of 94.22%, and the SVM had the lowest accuracy of 92.89%. These findings demonstrate the practicality of authenticating wood species by combining DART-TOF-MS with machine learning, and they indicate that ANN is the best model for wood species identification.

Practical investigation of direct analysis in real time mass spectrometry for fast screening of explosives

While the direct analysis in real time ionization coupled with mass spectrometry (DART-MS) is viable for the screening of trace explosives, a comprehensive evaluation is needed before its implementation in practice. This work has investigated the effectiveness and limitations of different DART-MS modules for the high-throughput and sensitive detection of nineteen organic explosive residues in four different categories deposited on several substrates. The Quickstrip method was used to optimize DART gas heater temperature as well as dopants. Four sample introducing strategies for DART-MS including transmission, thermal desorption, closed mesh, and direct-insert methods were implemented to analyze liquid and dried samples deposited on different substrates (e.g., fabric, leather, metal, plastic, and synthetic skin). It was found that representative explosives from each category could be detected with nanogram sensitivity and in less than 10 s. Therefore, DART-MS could provide prompt analysis of explosives for forensic applications.

Rapid evaluation of γ-aminobutyric acid in foodstuffs by direct real-time mass spectrometry.

Direct analysis in real-time ionization coupled with mass spectrometry (DART-MS) was first applied for the rapid determination of gamma-aminobutyric acid (GABA) in foods. Samples of germinated barley and fermented beans containing GABA at different levels were used, and the results were compared with those obtained by ultrahigh-performance liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry (UHPLC-ESI-MS). After a series of optimization, a simple sample extraction procedure using 30% methanol aqueous solution was conducted, followed by direct determination of sample extracts without chromatographic separation or prior derivatization. The optimized DART-MS method exhibited low limits of detection (0.040 mg·kg-1) and good recovery rates (88.6%-104%). The Aspergillus oryzae-fermented black beans produced the highest amount GABA. The results for the samples slightly varied between DART-MS and UHPLC-ESI-MS. Current findings indicate that DART-MS could be a high-throughput alternative to classic UHPLC-ESI-MS.

Rapid Determination of Capsaicin and Dihydrocapsaicin in Fermented Pepper Paste by Direct Analysis in Real Time Mass Spectrometry

A fast analytical method by direct analysis in real time ionization coupled to mass spectrometer (DART-MS/MS) has been developed for the estimate the capsaicin (CAP) and dihydrocapsaicin (DHCP) concentration in fermented pepper paste. Firstly, these mass fragmentation schemes of CAP and DHCP by DART-MS/MS are proposed, and compared with those of electrospray ionization source (ESI). After conducting a series of optimizations, the samples were extracted by a simple procedure using acetonitrile, the samples extracts were then directly evaluated by DART-MS/MS without chromatographic separation. A limit of detection (LOD) of 0.0234 and 0.0510 μg/mL was achieved for CAP and DHCP, respectively. The results obtained with the newly developed DART-MS/MS method are in good agreement with those by the conventional ultra-high-performance liquid chromatography-electrospray ionization-mass spectrometry method. The results showed that DART-MS/MS is a high-throughput tool for determination of CAP and DHCP concentration in food products.

Authenticity assessment of garlic using a metabolomic approach based on high resolution mass spectrometry

Depending on conditions in a growing locality and several other factors, marketed garlics (Allium sativum L.) may largely differ in content of flavour significant compounds and other biologically active components. To enable verification of tradeŕs declarations on the geographic origin, a new analytical, metabolomic fingerprinting, was employed for analysis of 47 samples of garlic with the designated country of origin Czech Republic, Spain and China. Non-target screening of metabolome components occurring in garlic extracts was performed employing following three instrumental platforms based on high resolution mass spectrometry (HRMS): (i) ambient mass spectrometry utilizing direct analysis in real time ionization (DART) ion source coupled to HRMS; (ii) direct infusion (DI) of sample into electrospray ion source (ESI) coupled to HRMS; (iii) high performance liquid chromatography (HPLC) – ESI – HRMS. Statistical models (Orthogonal Partial Least Squares-Discriminant Analysis, OPLS-DA) models were constructed on generated data with the aim to identify the best HRMS technique enabling a reliable differentiation of a country of origin. The best prediction ability, up to 100%, was obtained by processing the data generated by HPLC-HRMS. Alliin, phosphatidylcholine (16:0/18:2), arginine, dehydroalanine, phosphatidylethanolamine (16:0/22:6), L-γ-Glutamyl-S-allyl-l-cysteine and choline glycerolphosphate, were identified as compounds most contributing to a correct classification of the samples.

A rapid screening of histamine concentration in fish fillet by direct analysis in real time mass spectrometry (DART-MS)

Histamine is a biogenic amine causing scombroid foodborne poisoning. A rapid determination of the amine is effective in preventing the distribution of histamine-accumulated foods to market. Conventional methods for the determination of histamine concentration in foods include analyses by high performance liquid chromatography (HPLC). The present study tried to utilize a direct analysis in real-time ionization coupled to mass spectrometer (DART-MS) to estimate the histamine concentration in fish filets as an alternative to HPLC. The DART-MS responses to histamine and 1,8-diaminooctane as an internal standard were highly dependent on heater temperature; the highest responses were obtained at 400 °C. Histamine was spiked from 16.3 mg/kg to 407.0 mg/kg in tuna and yellowtail filets to obtain contaminated samples. The contaminated samples were homogenized with 0.1 mM EDTA containing 1,8-diaminooctane. The filtrates of the suspension were analyzed by DART-MS, and peak areas corresponding to the histamine and internal standard were obtained. The ratios of the histamine peaks to the internal standard peaks increased with higher histamine concentrations in the fish filets. The high linearity between the histamine concentrations and peak area ratios and the determination coefficient was more than 0.95. The results suggested that DART-MS is an attractive tool as a rapid screening method for determining histamine concentrations in fish filets.

Direct analysis in real time high resolution mass spectrometry as a tool for rapid characterization of mind-altering plant materials and revelation of supplement adulteration – The case of Kanna

We demonstrate the utility of direct analysis in real time ionization coupled with high resolution time-of-flight mass spectrometry (DART-HRTOFMS) in revealing the adulteration of commercially available Sceletium tortuosum, a mind-altering plant-based drug commonly known as Kanna. Accurate masses consistent with alkaloids previously isolated from S. tortuosum plant material enabled identification of the products as Kanna, and in-source collision-induced dissociation (CID) confirmed the presence of one of these alkaloids, hordenine, while simultaneously revealing the presence of an adulterant. The stimulant ephedrine, which has been banned in herbal products and supplements, was confirmed to be present in a sample through the use of in-source CID. High-throughput DART-HRTOFMS was shown to be a powerful tool to not only screen plant-based drugs of abuse for psychotropic alkaloids, but also to reveal the presence of scheduled substances and adulterants.

Analysis of anabolic androgenic steroids by direct analysis in real time ionization with time-of-flight mass spectrometry

We verified applicability of direct analysis in real time ionization coupled with a time-of-flight mass spectrometer (DART-MS) for detection of anabolic androgenic steroids in supplements and pharmaceuticals. DART-MS was optimized for the analysis of eleven frequently misused anabolic androgenic steroids and their derivatives. Real supplement tablets and injectable oil solutions were used to verify applicability of the method. It was found that anabolic androgenic steroids can be analyzed directly without any sample pre-treatment, which reduces the sample preparation time and hence the overall analysis time. The resulting DART-MS method is suitable for rapid routine qualitative screening of anabolic androgenic steroids in simple sample matrices. It has a great potential in the field of adulterated and counterfeited anabolic steroid pharmaceuticals and supplements.

Authentication of milk and milk-based foods by direct analysis in real time ionization–high resolution mass spectrometry (DART–HRMS) technique: A critical assessment

The potential of direct analysis in real time (DART) ambient ionization technique coupled with high resolution mass spectrometry (HRMS) in authentication of milk and dairy products was critically assessed. In particular case, DART–HRMS was used for several scenarios: (i) discrimination among milks obtained from various farm animal species (cow, goat, and sheep), (ii) discrimination between cows' milk produced in conventional and organic farming, and, (iii) detection of vegetable oil added to a milk-based product (soft cheese). For this purpose, a rapid profiling procedure based on examination of milk/cheese toluene extracts, was implemented. The obtained triacylglycerol (TAG) profiles (mass spectra) were processed with principal component analysis (PCA) and linear discriminant analysis (LDA). Based on LDA model, reliable differentiation of cows' milk samples and goats'/sheep's milk was possible. The DART–HRMS procedure also allowed distinguishing milk mixtures prepared at adulteration level of 50% (v/v). The capability to recognize milk from conventional and organic farming was rather low, poor classification rates of the LDA model were obtained. On the other hand, reliable detection of the presence of vegetable oils (rapeseed, sunflower, and soybean), added to soft cheese at amount as low as 1% (w/w), was possible. Additionally, the quality of added oil in terms of degree of its oxidation could be documented.

Evaluation of direct analysis in real time ionization–mass spectrometry (DART–MS) in fish metabolomics aimed to assess the response to dietary supplementation

Ambient mass spectrometry employing a direct analysis in real time (DART) ion source coupled to a medium high-resolution/accurate mass time-of-flight mass spectrometer (TOFMS) was used as a rapid tool for metabolomic fingerprinting to study the effects of supplemental feeding with cereals (triticale) on the composition of muscle metabolites of common carp (Cyprinus carpio L.).First, the sample extraction and DART–TOFMS instrumental conditions were optimized to obtain the broadest possible representation of ionizable compounds occurring in the extracts obtained from common carp muscle. To this end, a simultaneous (all-in-one) extraction procedure was developed employing water and cyclohexane mixture as the extraction solvents. Under these conditions both polar as well as non-polar metabolites were isolated within a single extraction step. Next, the metabolomic fingerprints (mass spectra) of a large set of common carp muscle extracts were acquired. Finally, the experimental data were statistically evaluated using principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA).Using this approach, differentiation of common carp muscle in response to dietary supplementation (feeding with and without cereals) was feasible. Correct classification was obtained based on the assessment of polar and as well as non-polar extracts fingerprints. The current study showed that DART–TOFMS metabolomic fingerprinting represents a rapid and powerful analytical strategy enabling differentiation of common carp muscles according to feeding history by recording metabolomic fingerprints of ionizable components under the conditions of ambient MS.

Direct analysis in real time-mass spectrometry (DART-MS) for rapid qualitative screening of toxic glycols in glycerin-containing products

In 2007, the United States Food and Drug Administration released guidance recommending testing of glycerin used in regulated consumer products, such as cough syrup preparations, toothpaste, and other pharmaceutical and food products, for the toxic compounds ethylene glycol and diethylene glycol. Regulatory laboratories routinely test glycerin, and products containing glycerin or related compounds for these toxic glycols, using an official gas chromatographic method, to ensure the safety of these products. The current work describes a companion technique to compliment this GC-FID method utilizing Orbitrap mass spectrometry with direct analysis in real time ionization to rapidly screen these samples qualitatively, with results in as little as five seconds, with no sample preparation required. This allows the more time and resource intensive method to be reserved for those rare cases when these compounds are detected, potentially greatly improving laboratory efficiency. The technique was evaluated for qualitative sensitivity and repeatability, and compared against the GC-FID method. The method appears to perform well against these metrics.

Application of direct analysis in real time ionization–mass spectrometry (DART–MS) in chicken meat metabolomics aiming at the retrospective control of feed fraud

Metabolomic fingerprinting enabled by ambient mass spectrometry employing a direct analysis in real time (DART) ion source coupled to a medium–high resolution/accurate mass time-of-flight mass spectrometer (TOFMS) was used as a tool for differentiation between chickens fed by feed that contained 5–8 % (w/w) of chicken bone meal (a banned component) and those representing a reference group, i.e. grown otherwise under the same conditions. In the first step, the sample extraction and DART–TOFMS instrumental conditions were optimized to obtain the broadest possible representation of ionizable compounds occurring in the extracts obtained from chicken muscle and feed on which experimental animals were grown. To this end, a simultaneous (all-in-one) extraction procedure was developed employing water and cyclohexane mixture as the extraction solvents. Under these conditions both polar as well as non-polar metabolites were isolated within a single extraction step. In the next step, metabolomic fingerprints of a large set of chicken muscle and feed extracts were acquired. In the final phase, the experimental data were statistically evaluated using principal component analysis and orthogonal partial least squares discriminant analysis. In general, differentiation of chicken muscle according to diet (feed with and without the addition of chicken bone meal) was feasible. Additional experiments conducted after 6 months confirmed applicability of this approach. Correct classification was obtained based on the assessment of polar as well as non-polar extracts fingerprints. However, the analysis of non-polar extracts showed that the pattern of triacylglycerols is more prone to seasonal variability and/or type of raw materials used during feed preparation which obscures the bone meal impact to some extent.

Rapid monitoring of heat-accelerated reactions in vegetable oils using direct analysis in real time ionization coupled with high resolution mass spectrometry

Transmission-mode direct analysis in real time ionization coupled with high resolution mass spectrometry (TM-DART–HRMS) was used to monitor chemical changes in various vegetable oils (olive, rapeseed, soybean and sunflower oil) during their thermally-induced oxidation. This novel instrumental approach enabled rapid fingerprinting of examined samples and detection of numerous sample components, such as triacylglycerols (TAGs), phytosterols, free fatty acids (FFA), and their respective oxidation products. Mass spectra obtained from DART were processed with the use of principal component analysis (PCA) in order to assess the compositional differences between heated and non-heated samples. Good correlation was observed between the normalized intensities of the pre-selected ion corresponding to mono-oxidized TAG and ‘classic’ criterion represented by the levels of TAG polymers determined by high performance-size exclusion chromatography with refractometric detection (HP-SEC–RID).

Rapid analysis of caffeine in various coffee samples employing direct analysis in real-time ionization–high-resolution mass spectrometry

The development and use of a fast method employing a direct analysis in real time (DART) ion source coupled to high-resolution time-of-flight mass spectrometry (TOFMS) for the quantitative analysis of caffeine in various coffee samples has been demonstrated in this study. A simple sample extraction procedure employing hot water was followed by direct, high-throughput (<1 min per run) examination of the extracts spread on a glass rod under optimized conditions of ambient mass spectrometry, without any prior chromatographic separation. For quantification of caffeine using DART-TOFMS, an external calibration was used. Isotopically labeled caffeine was used to compensate for the variations of the ion intensities of caffeine signal. Recoveries of the DART-TOFMS method were 97% for instant coffee at the spiking levels of 20 and 60 mg/g, respectively, while for roasted ground coffee, the obtained values were 106% and 107% at the spiking levels of 10 and 30 mg/g, respectively. The repeatability of the whole analytical procedure (expressed as relative standard deviation, RSD, %) was <5% for all tested spiking levels and matrices. Since the linearity range of the method was relatively narrow (two orders of magnitude), an optimization of sample dilution prior the DART-TOFMS measurement to avoid saturation of the detector was needed.

The coupling of direct analysis in real time ionization to Fourier transform ion cyclotron resonance mass spectrometry for ultrahigh-resolution mass analysis

Direct Analysis in Real Time (DART) is an ambient ionization technique for mass spectrometry that provides rapid and sensitive analyses with little or no sample preparation. DART has been reported primarily for mass analyzers of low to moderate resolving power such as quadrupole ion traps and time-of-flight (TOF) mass spectrometers. In the current work, a custom-built DART source has been successfully coupled to two different Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers for the first time. Comparison of spectra of the isobaric compounds, diisopropyl methylphosphonate and theophylline, acquired by 4.7 T FT-ICR MS and TOF MS, demonstrates that the TOF resolving power can be insufficient for compositionally complex samples. 9.4 T FT-ICR MS yielded the highest mass resolving power yet reported with DART ionization for 1,2-benzanthracene and 9,10-diphenylanthracene. Polycyclic aromatic hydrocarbons exhibit a spatial dependence in ionization mechanisms between the DART source and the mass spectrometer. The feasibility of analyzing a variety of samples was established with the introduction and analysis of food products and crude oil samples. DART FT-ICR MS provides complex sample analysis that is rapid, highly selective and information-rich, but limited to relatively low-mass analytes.