Selected Ion Flow Tube Mass Research Articles

Nighttime chemistry of furanoids and terpenes: Temperature dependent kinetics with NO3 radicals and insights into the reaction mechanism

In this study, the gas phase reaction of NO3 radical with three furanoids, furan (F), 2-methylfuran (2-MF) and 2,5-dimethylfuran (2,5-DMF) were investigated using a relative rate method in a temperature regulated atmospheric simulation chamber (THALAMOS). As part of this study, the temperature dependence of two monoterpenes, α-pinene (α-P) and 2-carene (2-C), that were used as reference molecules, is also reported. The kinetic measurements were performed in the range of 263–373 K, atmospheric pressure using zero air as bath gas. The reaction was followed using Selected ion flow tube mass spectrometry (SIFT-MS) to monitor in real time the mixing ratios of the investigated species. The corresponding Arrhenius expressions obtained were:kα−P+NO3(263−378K)=(1.32±0.16)×10−12×e462±70Tcm3molecule‐1s‐1.k2−C+NO3296–433K=8.77±2.71×10−13×e904±96Tcm3molecule‐1s‐1.kF+NO3263−353K=7.55±1.96×10−13×e254±79Tcm3molecule‐1s‐1.k2−MF+NO3263−373K=7.76±2.62×10−13×e922±262Tcm3molecule‐1s‐1.k2,5−DMF+NO3298–353K=2.58±0.77×10−13×e1692±136Tcm3molecule‐1s‐1.Where the estimated uncertainties include the 1σ precision of the fit and the estimated uncertainty in the precision of the Arhenius fit of the reference compound. In the case of furanoids, the negative temperature-dependence of the rate coefficients shows that the reaction mechanism is complex, indicating that the reaction involves the formation of an adduct that could lead either to NO3 addition to the double bond, as well as, in the case of 2-MF and 2,5-DMF, the H-abstraction from the methyl group attached to the ring. In addition to the kinetics measurements, the major products formed from the reaction of furan and 2,5-DMF with NO3 were studied. The two identified products from the reaction of furan with NO3, were 3H-furan-2-one (C4H4O2) and 2-butenedial (C4H4O2), formed by NO3 addition to the double bond of the furan ring. 3-Hexene-2,5-dione (C6H8O2) and 5-methylfurfural (C6H6O2) are the two major products of 2,5-DMF reaction with NO3, linked to the addition and abstraction pathways, respectively. Considering that 5-methylfurfural is the only primary product of the H elimination pathway of 2,5-DMF, the determination of its formation yields as a function of temperature, allowed us to extract the temperature dependence of the rate coefficients of the abstraction and addition pathways.Overall, the NO3 oxidation of the studied furanoids, is expected to be the dominant tropospheric loss process, in the studied temperature range.

High and low pathogenicity avian influenza virus discrimination and prediction based on volatile organic compounds signature by SIFT-MS: a proof-of-concept study

High and low pathogenicity avian influenza viruses (HPAIV, LPAIV) are the primary causes of poultry diseases worldwide. HPAIV and LPAIV constitute a major threat to the global poultry industry. Therefore, early detection and well-adapted surveillance strategies are of the utmost importance to control the spread of these viruses. Volatile Organic Compounds (VOCs) released from living organisms have been investigated over the last decades as a diagnostic strategy. Mass spectrometry instruments can analyze VOCs emitted upon viral infection. Selected ion flow tube mass spectrometry (SIFT-MS) enables direct analysis of cell headspace in less than 20 min. As a proof-of-concept study, we investigated the ability of a SIFT-MS coupled sparse Partial Least Square-Discriminant Analysis analytical workflow to discriminate IAV-infected cells. Supernatants of HPAIV, LPAIV, and control cells were collected from 1 to 72 h post-infection and analyzed using our analytical workflow. At each collection point, VOCs' signatures were first identified based on four independent experiments and then used to discriminate the infectious status of external samples. Our results indicate that the identified VOCs signatures successfully discriminate, as early as 1-h post-infection, infected cells from the control cells and differentiated the HPAIV from the LPAIV infection. These results suggest a virus-dependent VOCs signature. Overall, the external samples' status was identified with 96.67% sensitivity, 100% specificity, and 97.78% general accuracy.

Investigation of odor pollution by utilizing selected ion flow tube mass spectrometry (SIFT-MS) and principal component analysis (PCA).

Odor pollution, also referred to as odor nuisance, is a growing environmental concern that is significantly associated with mental health. Once emitted into the air, the concentration of odorous substances varies considerably with wind conditions, leading to difficulties in timely sampling. In the present study, we employed selected ion flow tube mass spectrometry (SIFT-MS) to measure 22 odor-producing molecules continuously in an urban-rural complex city. In addition, we applied statistical analyses, principal component analysis (PCA), and a conditional probability function (CPF) to the datasets obtained from SIFT-MS to identify the odor characteristics at two study sites. At site A, odorants related to livestock farming and industry showed high factor loadings on principal components (PCs) from the PCA. In contrast, we estimated that the odorous gaseous chemicals affecting site B were closely related to sewage treatment and municipal solid waste disposal. Similar CPF patterns of grouped substances from the PCA supported the association between potential odor sources and specific odorants at site B, which helped estimate possible source locations. Consequently, our findings indicate that continuous monitoring of odorous substances using SIFT-MS can be an effective way to provide sufficient information on odor-producing molecules, leading to the clear identification of odor characteristics despite the high variability of odorous substances.

An Overview of Recent Analytical Techniques for Air Quality Monitoring and Assessment

Abstract: Access to clean air, a vital necessity for life, faces severe constraints globally due to industrialization and urbanization, leading to widespread air quality deterioration. To safeguard human health and the environment from detrimental effects, the essential components of proper monitoring, assessment, and management of air quality are paramount. Conventional air quality analytical techniques such as gas chromatography/ mass spectrometry, selected ion flow tube mass spectrometry, thermal desorption/ gas chromatography, and mass spectrometry are widely used for air quality analysis. These methods, however, are laborious, necessitate sample preparation, require expansive and hazardous reagents, and have a high cost of equipment and maintenance. As such, more rapid, sensitive, specific, cost-effective, portable, user-friendly, and environmentally friendly analytical tools are required for efficient air quality monitoring and control. Over the years, various techniques have emerged to address these challenges, including mobile sensors, microbial monitoring, the Internet of Things (IoT), biomonitoring, and bio- and nanosensors in both indoor and outdoor settings. This paper offers an overview of recent advancements in air quality monitoring and assessment methods. The review encompasses sample preparations for air pollutants, data analysis methodologies, and monitoring strategies. It also delves into the crucial role of microorganisms in air quality analysis. Additionally, the paper explores the applications of the Internet of Things (IoT) and biosensors in air quality monitoring and assessment, elucidating their roles in advancing these endeavors. The paper concludes by presenting insightful perspectives on the current state of air quality monitoring techniques and outlining future directions for research and development in this critical field.

Lethal and sublethal heat-exposure of bed bugs (Cimex lectularius L.) causes alarm pheromone emission and elicits a movement response in nearby recipients

Many gregarious insect species use aggregation and alarm pheromones. The bed bug, Cimex lectularius L., emits an alarm pheromone (AP), a 70/30 blend of (E)-2-hexenal and (E)-2-octenal, when threatened. Bed bugs avoid temperatures above 43 °C, which are lethal to bugs and used commercially as spatial heat treatments to manage infestations. However, the interaction of bed bug AP in heat avoidance has not been investigated. The goal of this research was to: 1) determine if bed bugs emit AP as an alarm response to heat exposure, and 2) quantify the behavioral responses of conspecifics to AP emitted by heat-exposed bed bugs. Using a selected ion flow tube mass spectrometer, we found that bed bugs responded to lethal and sublethal heat exposure by emitting AP. The Harlan laboratory population emitted more pheromone than a laboratory adapted field population from Florida (McCall). Harlan females emitted the most AP, followed by Harlan males, McCall females and males. In separate behavioral experiments, we showed that conspecifics (i.e., recipients) reacted to AP released by heat exposed bed bugs (i.e., emitters) by frantically moving within 50 mm and 100 mm test arenas. The Harlan recipients reacted to AP in 100 mm areas, whereas the McCall strain did not, indicating a short area of effectiveness of the AP. Synthetic AP components tested in behavioral experiments caused identical effects as the natural AP blend released by heat-exposed bed bugs.

Quantitative Analysis of NDMA in Drug Products: A Proposed High-Throughput Approach Using Headspace–SIFT-MS

Since the initial 2018 recall of angiotensin receptor blockers due to unacceptable levels of mutagenic N-nitrosodimethylamine (NDMA) impurity, numerous drug products delivering diverse active pharmaceutical ingredients (APIs) have been recalled. Regulators and the industry are working together to understand and address this widescale problem. Conventional analysis of NDMA utilizes liquid or gas chromatography-based procedures that can involve complicated sample preparation and slow sample analysis. Selected ion flow tube mass spectrometry (SIFT-MS) analyses NDMA directly in the gas phase using soft chemical ionization, with an LOQ of 2 ng g−1. Through the novel application of the multiple headspace extraction (MHE) technique, NDMA was quantified directly and rapidly from the drug product without dissolution, at levels well below the regulatory acceptable intake of 96 ng day−1. A comparative analysis of recalled metformin using MHE-SIFT-MS and a conventional liquid chromatography–mass spectrometry/mass spectrometry (LC-MS/MS) method showed good agreement. Use of the novel MHE-SIFT-MS approach may enable a wider screening of drug products to be conducted, since it provides around a three-fold increase in daily sample throughput.

Improved volatiles analysis workflows using automated selected ion flow tube mass spectrometry (SIFT-MS)

Selected ion flow tube mass spectrometry (SIFT-MS) is a recent addition to the routine analysis and research laboratory toolkit, primarily as a quantitative tool.

Investigation and mechanism of headspace corrosion in metal cans filled chicken noodle soup

AbstractThis study demonstrated a method to investigate corrosion formation in the headspace of canned chicken noodle soup. In this method, Selected Ion Flow Tube–Mass Spectrometer was used to identify and quantify chemical compounds in raw and cooked chicken noodle soup and those that migrated towards the polymer coating of the metal cans. Scanning electron microscopy (SEM) was used to detect the appearance of breaches in the coating of the tested cans, and energy dispersive X‐ray spectroscopy (EDS) allowed for analysis of the elemental composition of the internal walls of the tested cans. Inductively coupled plasma–mass spectrometry (ICP‐MS) provided information about the migration of iron and tin from the internal walls of the cans into the packaged soups. SEM images showed that breaches developed in the coating of the tested cans when corrosion occurred. The EDS analyses showed that tin and iron exposures were associated with extra peaks in the EDS. These peaks were attributed to sulphur. From the results obtained, it was concluded that the process of heat retorting contributed to the formation of sulphur‐containing volatile compounds that bonded to the coating in the headspace of the tested cans. These then penetrated the protective coating and facilitated avenues for other oxidative chemicals in the product to cause corrosion and staining. Results from the ICP‐MS analyses showed that tin and iron subsequently migrated from the corroded cans toward the chicken soup. These results thus showed how corrosive compounds in a retorted food initiated corrosion in metal cans.

Products and yields for the NO3 radical initiated atmospheric degradation of 2-methylfuran (2-MF, CH3–C4H3O)

Furans represent a group of oxygenated, heterocyclic, organic compounds that are emitted during biomass burning (BB). Notably, these compounds undergo rapid oxidation, a process observed both during the day and at night. Methylated furanoids comprise a large fraction of total furan emissions. Recent kinetic studies suggest that the NO3 initiated degradation of methylated furans is the dominant reaction pathway during nighttime, and with significant contribution on daytime. The aim of this study is to investigate the degradation products and the reaction mechanism of 2-methylfuran (2-MF) reaction with NO3 radicals using two atmospheric simulation chambers: CHARME (Chamber for the Atmospheric Reactivity and the Metrology of the Environment, Dunkerque, France) and THALAMOS (Thermally Regulated Atmospheric Simulation Chamber, Douai, France). All experiments were carried out at ambient temperature, (294 ± 2) K and atmospheric pressure (760 Torr, zero air). Oxidation products were qualitatively and quantitatively characterized using multiple, complementary detection techniques. Gas phase major and minor products were detected via offline GC-EI-MS (Gas chromatography - Electronic Impact - Mass Spectrometry) after trapping the gas-phase mixture on different adsorption media. PTR-ToF-MS (Proton Transfer Mass Reaction – Time of Flight – Mass Spectrometer, CHARME) and SIFT-MS (Selected Ion Flow Tube Mass Spectrometry, THALAMOS) were used on-line to monitor reactants and major products and to determine the end-product yields. 4-Oxo-2-pentenal (H(O)CCHCHC(O)CH3), and 2(5H)-furanone, 5-methyl, 5-nitrooxy ((CH3)C(ONO2)(C4H2O2)) were detected as major products with yields (62 ± 15) % and (26 ± 3) %, respectively. In-situ FTIR (Fourier Transform Infrared Spectroscopy) along with quantum mechanical molecular calculations revealed that organic nitrates and dinitrates were also formed. Secondary organic aerosols (SOA) formation, in the presence of ammonium sulfate seed, was also monitored using SMPS-CPC (Scanning Mobility Particle Sizer-Condensation Particle Counter). The size distribution and the mass concentration of the particles were determined for 2-MF concentration between 80 and 531 ppbv leading to SOA yields 1.03–2.23 %. Finally, SOA formed were chemically characterized using ESI-LC-QToF-MS/MS (Electrospray Ionization Liquid Chromatography – Quadrupole - Time of Flight - Tandem Mass Spectrometer) revealing that oligomers, e.g. highly oxygenated molecules (HOMs) were also formed. Based on our experimental observations, a reaction mechanism is proposed. NO3 radical is predominately added to the C2/C5 double bond of 2-MF, while the H atom abstraction channel, is estimated to be of minor importance. Results from this work provide detailed information about the NO3 radical initiated oxidation of 2-MF that can be used in chemical transport models to simulate the ageing processes occurring in biomass burning plumes.

Non-destructive egg breed separation using advanced VOC analytical techniques HSSE-GC-MS, PTR-TOF-MS, and SIFT-MS: Assessment of performance and systems’ complementarity

Over the past decade, advanced analytical techniques have been utilized to examine volatile organic compounds (VOCs) in eggs. These VOCs offer valuable insights into factors such as freshness, fertility, the presence of cracks, embryo sex, and breed. In our study, we assessed three mass spectrometry-based systems (headspace sorptive extraction gas chromatography-mass spectrometry; HSSE-GC-MS, proton transfer reaction time-of-flight-mass spectrometry; PTR-TOF-MS; and selected ion flow tube mass spectrometry; SIFT-MS) to analyze and identify VOCs present in intact hatching eggs from three distinct breeds (Dekalb white layer, Shaver brown layer, and Ross 308 broiler). The eggs were sampled on incubation days 2 and 8, to identify VOCs that distinguish breeds irrespective of incubation day. VOC measurements were conducted on 15 eggs per breed by placing them together with PDMS-coated stir bars inside inert Teflon® air sampling bags. After an accumulation period of 2 h, the headspace was analyzed using PTR-TOF-MS and SIFT-MS, while the VOCs adsorbed onto the stir bars were analyzed using GC-MS for additional compound identification. Partial least squares discriminant analysis (PLS-DA) models were constructed for breed differentiation, and variable selection was performed. As a result, 111 VOCs were identified using HSSE-GC-MS, with alcohols and esters being the most abundant. The PLS-DA models demonstrated the efficacy of breed discrimination, with the HSSE-GC-MS and the PTR-TOF-MS exhibiting the highest balanced accuracy of 95.5 % using a reduced set of 11 VOCs and 5 product ions, respectively. The SIFT-MS model had a balanced accuracy of 92.8 % with a reduced set of 11 product ions. Furthermore, complementarity was observed between HSSE-GC-MS, which primarily selected higher molecular weight VOCs, and PTR-TOF-MS and SIFT-MS. A higher correlation was found for compound abundances between the HSSE-GC-MS and the PTR-TOF-MS relative to the SIFT-MS, indicating that the PTR-TOF-MS was better suited to quantify specific compounds identified by the HSSE-GC-MS. Finally, the findings support the presence of VOCs originating from both synthetic and natural sources, highlighting the ability of the VOC analysis systems to non-destructively perform quality control and reveal differences in management practices or biological information encoded in eggs.

Real-Time Phytoncide Monitoring in Forests: A Comparative Study of SIFT-MS and Conventional GC-MS Methods

Conventional gas chromatography-mass spectrometry (GC-MS) analysis methods for measuring the concentration of phytoncides in forests are limited because of the need for an extended human presence in forests, the risk of errors, and contamination. To overcome these issues, this study introduces real-time measurement devices and selected ion flow tube mass spectrometry (SIFT-MS) as potential replacements. This study was conducted in the Hongneung Experimental Forest between 19 and 21 November 2019. A correlation analysis and independent samples t-test were performed to compare the GC-MS and SIFT-MS techniques. The diurnal patterns and trends in the phytoncide concentrations analyzed using the GC-MS and SIFT-MS methods were similar, suggesting the potential replacement of GC-MS with SIFT-MS. While both methods revealed similar major components in the daytime nonvolatile organic compounds (NVOCs), with pinenes comprising approximately half of the total percentage, the 24 h SIFT-MS analysis indicated reduced proportions of pinenes and benzaldehyde, along with the detection of more diverse NVOC compounds at night. Additionally, the studies indicated that GC-MS exhibited slightly higher selectivity, resulting in the detection of fewer NVOC compounds with SIFT-MS. The correlation analysis between the microclimate indicators and phytoncide measurement methods revealed differences: GC-MS with a mini pump showed positive correlations with fine dust and industrially derived VOCs, while the 24 h real-time measurements exhibited strong negative correlations. Consequently, while the GC-MS and SIFT-MS methods exhibited both similarities and differences in phytoncide concentrations, an independent samples t-test, confirming no statistically significant differences between the two methods, suggests the suitability of adopting SIFT-MS over GC-MS for phytoncide collection and analysis in forest environments. Nevertheless, this study contributes to the literature by comparing outdoor phytoncide levels using the GC-MS and SIFT-MS methodologies. These findings, which show that the methods are closely aligned, can guide future researchers in considering SIFT-MS equipment for phytoncide studies, offering a more accessible and efficient option with real-time capabilities.

Rate coefficients for the gas‐phase OH + furan (C4H4O) reaction between 273 and 353 K

AbstractRate coefficients, k1, for the gas‐phase OH radical reaction with the heterocyclic ether C4H4O (1,4‐epoxybuta‐1,3‐diene, furan) were measured over the temperature range 273–353 K at 760 Torr (syn. air). Experiments were performed using: (i) the photochemical smog chamber THALAMOS (thermally regulated atmospheric simulation chamber, IMT NE, Douai‐France) equipped with Fourier Transform Infrared (FTIR) and Selected Ion Flow Tube Mass Spectrometry (SIFT‐MS) detection methods and (ii) a photochemical reactor coupled with FTIR spectroscopy (PCR, University of Crete, Greece). k1(273–353 K) was measured using a relative rate (RR) method, in which the loss of furan was measured relative to the loss of reference compounds with well‐established OH reaction rate coefficients. k1(273–353 K) was found to be well represented by the Arrhenius expression (1.30 ± 0.12) × 10−11 exp[(336 ± 20)/T] cm3 molecule−1 s−1, with k1(296 K) measured to be (4.07 ± 0.32) × 10−11 cm3 molecule−1 s−1. The k1(296 K) and pre‐exponential quoted error limits are 2σ and include estimated systematic errors in the reference rate coefficients. The observed negative temperature dependence is consistent with a reaction mechanism involving the OH radical association to a furan double bond. Quantum mechanical molecular calculations show that OH addition to the α‐carbon (ΔHr(296 K) = −121.5 kJ mol−1) is thermochemically favored over the β‐carbon (ΔHr(296 K) = −52.9 kJ mol−1) addition. The OH‐furan adduct was found to be stable over the temperature range of the present measurements. Maleic anhydride (C4H2O3) was identified as a minor reaction product, 3% lower‐limit yield, demonstrating a non‐ring‐opening active reaction channel. The present results are critically compared with results from previous studies of the OH + furan reaction rate coefficient. The infrared spectrum of furan was measured as part of this study and its estimated climate metrics are reported.

Exhaled Breath Analysis Using Selected Ion Flow Tube Mass Spectrometry and Disease Severity in Heart Failure.

Exhaled breath volatile organic compounds (VOCs) are elevated in heart failure (HF). The ability of VOCs to predict long term cardiovascular mortality and morbidity has not been independently verified. In 55 patients admitted with acute decompensated heart failure (ADHF), we measured exhaled breath acetone and pentane levels upon admission and after 48 h of diuresis. In a separate cohort of 51 cardiac patients undergoing cardiopulmonary exercise testing (CPET), we measured exhaled breath acetone and pentane levels before and at peak exercise. In the ADHF cohort, admission acetone levels correlated with lower left ventricular ejection fraction (LVEF, r = -0.297, p = 0.035). Greater weight loss with diuretic therapy correlated with a greater reduction in both acetone levels (r = -0.398, p = 0.003) and pentane levels (r = -0.309, p = 0.021). In patients with above-median weight loss (≥4.5 kg), patients demonstrated significantly greater percentage reduction in acetone (59% reduction vs. 7% increase, p < 0.001) and pentane (23% reduction vs. 2% reduction, p = 0.008). In the CPET cohort, admission acetone and pentane levels correlated with higher VE/VCO2 (r = 0.39, p = 0.005), (r = 0.035, p = 0.014). However, there were no significant correlations between baseline or peak exercise acetone and pentane levels and peak VO2. In longitudinal follow-up with a median duration of 33 months, patients with elevated exhaled acetone and pentane levels experienced higher composite adverse events of death, ventricular assist device implantation, or orthotopic heart transplantation. In patients admitted with ADHF, higher exhaled breath acetone levels are associated with lower LVEF and poorer outcomes, and greater reductions in exhaled breath acetone and pentane tracked with greater weight loss. Exhaled acetone and pentane may be novel biomarkers in heart failure worthy of future investigation.

Effects of Short-term Electronic(e)-Cigarette Aerosol Exposure in the Mouse Larynx.

The effects of electronic cigarettes (e-cigarettes) on the larynx are relatively unknown. This study examined the short-term effects of e-cigarette inhalation on cellular and inflammatory responses within the mouse laryngeal glottic and subglottic regions after exposure to pod-based devices (JUUL). Male C57BL6/J mice (8-9 weeks) were assigned to control (n = 9), JUUL flavors Mint (JMi; n = 10) or Mango (JMa; n = 10). JUUL mice were exposed to 2 h/day for 1, 5, and 10 days using the inExpose inhalation system. Control mice were in room air. Vocal fold (VF) epithelial thickness, cell proliferation, subglandular area and composition, inflammatory cell infiltration, and surface topography were evaluated in the harvested larynges. Mouse body weight and urinary nicotine biomarkers were also measured. Chemical analysis of JUUL aerosols was conducted using selective ion flow tube mass spectrometry. JUUL-exposed mice had reduced body weight after day 5. Urinary nicotine biomarker levels indicated successful JUUL exposure and metabolism. Quantitative analysis of JUUL aerosol indicated that chemical constituents differ between JMi and JMa flavors. VF epithelial thickness, cellular proliferation, glandular area, and surface topography remained unchanged after JUUL exposures. Acidic mucus content increased after 1 day of JMi exposure. VF macrophage and T-cell levels slightly increased after 10 days of JMi exposures. Short-term e-cigarette exposures cause minimal flavor- and region-specific cellular and inflammatory changes in the mouse larynx. This work provides a foundation for long-term studies to determine if these responses are altered with multiple e-cigarette components and concentrations. N/A Laryngoscope, 134:1316-1326, 2024.

Direct mass spectrometry analysis of exhaled human breath in real-time.

The molecular composition of exhaled human breath can reflect various physiological and pathological conditions. Considerable progress has been achieved over the past decade in real-time analysis of exhaled human breath using direct mass spectrometry methods, including selected ion flow tube mass spectrometry, proton transfer reaction mass spectrometry, extractive electrospray ionization mass spectrometry, secondary electrospray ionization mass spectrometry, acetone-assisted negative photoionization mass spectrometry, atmospheric pressure photoionization mass spectrometry, and low-pressure photoionization mass spectrometry. Here, recent developments in direct mass spectrometry analysis of exhaled human breath are reviewed with regard to analytical performance (chemical sensitivity, selectivity, quantitative capabilities) and applications of the developed methods in disease diagnosis, targeted molecular detection, and real-time metabolic monitoring.

Breath analysis combined with cardiopulmonary exercise testing and echocardiography for monitoring heart failure patients: the AEOLUS protocol

This paper describes the AEOLUS pilot study which combines breath analysis with cardiopulmonary exercise testing (CPET) and an echocardiographic examination for monitoring heart failure (HF) patients. Ten consecutive patients with a prior clinical diagnosis of HF with reduced left ventricular ejection fraction were prospectively enrolled together with 15 control patients with cardiovascular risk factors, including hypertension, type II diabetes or chronic ischemic heart disease. Breath samples were collected at rest and during CPET coupled with exercise stress echocardiography (CPET-ESE) protocol by means of needle trap micro-extraction and were analyzed through gas-chromatography coupled with mass spectrometry. The protocol also involved using of a selected ion flow tube mass spectrometer for a breath-by-breath isoprene and acetone analysis during exercise. At rest, HF patients showed increased breath levels of acetone and pentane, which are related to altered oxidation of fatty acids and oxidative stress, respectively. A significant positive correlation was observed between acetone and the gold standard biomarker NT-proBNP in plasma (r = 0.646, p < 0.001), both measured at rest. During exercise, some exhaled volatiles (e.g., isoprene) mirrored ventilatory and/or hemodynamic adaptation, whereas others (e.g., sulfide compounds and 3-hydroxy-2-butanone) depended on their origin. At peak effort, acetone levels in HF patients differed significantly from those of the control group, suggesting an altered myocardial and systemic metabolic adaptation to exercise for HF patients. These preliminary data suggest that concomitant acquisition of CPET-ESE and breath analysis is feasible and might provide additional clinical information on the metabolic maladaptation of HF patients to exercise. Such information may refine the identification of patients at higher risk of disease worsening.

How to Use Ion-Molecule Reaction Data Previously Obtained in Helium at 300 K in the New Generation of Selected Ion Flow Tube Mass Spectrometry Instruments Operating in Nitrogen at 393 K.

Selected ion flow tube mass spectrometry (SIFT-MS) instruments have significantly developed since this technique was introduced more than 20 years ago. Most studies of the ion-molecule reaction kinetics that are essential for accurate analyses of trace gases and vapors in air and breath were conducted in He carrier gas at 300 K, while the new SIFT-MS instruments (optimized to quantify concentrations down to parts per trillion by volume) operate with N2 carrier gas at 393 K. Thus, we pose the question of how to reuse the data from the extensive body of previous literature using He at room temperature in the new instruments operating with N2 carrier gas at elevated temperatures. Experimentally, we found the product ions to be qualitatively similar, although there were differences in the branching ratios, and some reaction rate coefficients were lower in the heated N2 carrier gas. The differences in the reaction kinetics may be attributed to temperature, an electric field in the current flow tubes, and the change from He to N2 carrier gas. These results highlight the importance of adopting an updated reaction kinetics library that accounts for the new instruments' specific conditions. In conclusion, almost all previous rate coefficients may be used after adjustment for higher temperatures, while some product ion branching ratios need to be updated.

Evaluation of Solvent Compatibilities for Headspace-SIFT-MS Analysis of Pharmaceutical Products

Procedures for determination of the residual solvent and volatile impurity content in pharmaceutical products usually rely on dissolution in a solvent, followed by headspace-gas chromatography (HS-GC) analysis. Whereas chromatographic systems can utilize a wide variety of solvents, direct-injection mass spectrometry (DIMS) techniques have fewer solvent options, because elimination of the chromatographic column means that the instrument is more susceptible to saturation. Since water has the lowest impact, it has almost always been the default solvent for DIMS. In this study, selected ion flow tube mass spectrometry (SIFT-MS)—a DIMS technique—was applied to the systematic evaluation of the proportion of solvent that can be utilized (with aqueous diluent) without causing instrument saturation and while maintaining satisfactory analytical performance. The solvents evaluated were N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), 1,3-dimethyl-2-imidazolidinone (DMI), dimethyl sulfoxide (DMSO), methanol, and triacetin. All solvents are compatible with headspace-SIFT-MS analysis at 5% (min) in water, while DMI, DMAC, and DMSO can be used at higher concentrations (50, 100, and 25%, respectively), though suffering substantial diminution of the limit of quantitation for non-polar analytes at higher proportions of non-aqueous solvent. Analytical performance was also evaluated using linearity, repeatability, and recovery measurements. This work demonstrates that organic solvents diluted in water can be utilized with headspace-SIFT-MS and provide an approach for evaluation of additional diluent solvents.

Early detection of Botrytis cinerea in strawberry fruit during quiescent infection using selected ion flow tube mass spectrometry (SIFT-MS)

Botrytis cinerea is a devastating pathogen that can cause huge postharvest losses of strawberry. Although this fungus usually infects strawberries through their flowers, symptoms mainly appear when fruit are fully mature. A fast and sensitive method to detect and quantify the fungal infection, prior to symptom development, is, therefore, needed. In this study, we explore the possibility of using the strawberry volatilome to identify biomarkers for B. cinerea infection. Strawberry flowers were inoculated with B. cinerea to mimic the natural infection. First, quantitative polymerase chain reaction (qPCR) was used to quantify B. cinerea in the strawberry fruit. The detection limit of qPCR for B. cinerea DNA extracted from strawberries was 0.01 ng. Subsequently, changes in the fruit volatilome at different fruit developmental stages were characterized using gas chromatography - mass spectrometry (GC–MS) and selected ion flow tube mass spectrometry (SIFT-MS). Based on GC–MS data, 1-octen-3-ol produced by B. cinerea was confirmed as a potential biomarker of B. cinerea infection. Moreover, the product ion NO+ 127, obtained by SIFT-MS measurements, was proposed as a potential biomarker for B. cinerea infection by comparing its relative level with that of 1-octen-3-ol (obtained by GC–MS) and B. cinerea (obtained by qPCR). Separate PLS regressions were carried out for each developmental stages, and 11 product ions were significantly altered at all developmental stages. Finally, PLS regressions using these 11 ions as variables allowed the discrimination between samples containing different amount of B. cinerea. This work showed that profiling the fruit's volatilome using SIFT-MS can be used as a potential alternative to detect B. cinerea during the quiescent stage of B. cinerea infection prior to symptom development. Moreover, the corresponding compounds of potential biomarkers suggest that the volatile changes caused by B. cinerea infection may contribute to strawberry defense.

Pharmaceutical Residual Solvent Analysis: A Comparison of GC-FID and SIFT-MS Performance

Residual solvents in pharmaceutical excipients, active pharmaceutical ingredients (APIs), and finished products are usually analyzed using gas chromatography (GC)-based techniques according to a pharmacopeial monograph, such as the United States Pharmacopeia’s (USP) chapter &lt;467&gt;. GC analyses are often slow, which limits sample throughput. Selected ion flow tube mass spectrometry (SIFT-MS) removes the rate-limiting chromatographic separation step, potentially offering faster sample analyses. This approach was demonstrated recently with the publication of an alternative SIFT-MS procedure which was successfully validated against the performance criteria in USP chapter &lt;1467&gt;. The present study expands upon the previous work by conducting a head-to-head comparison of GC-flame ionization detection (GC-FID) and SIFT-MS procedures. The results obtained in this cross-platform study demonstrated similar performance for the GC-FID and SIFT-MS procedures for linearity (R2 &gt; 0.94 and 0.97, respectively) and repeatability (&lt;17%RSD and &lt;10%RSD). For accuracy and recovery, acceptance criteria (within 20%) were achieved for most compounds across the two drug products (SIFT-MS suffered fewer failures, possibly due to shorter wait times prior to analysis). Additionally, SIFT-MS analyzed samples over 11-fold faster than GC-FID, increasing daily sample throughput and reducing the time taken to determine the result. This study therefore suggests that residual solvent analysis using SIFT-MS may support workflow improvements for pharmaceutical manufacturers.