Direct Analysis of Soil Composition for Source Apportionment by Laser Ablation Single-Particle Aerosol Mass Spectrometry.

Soil has always been the most complex biomaterial on the planet. The rapid determination of the components in the soil and their original source is a prerequisite for soil quality, environmental, and human health risk assessments. In this study, the chemical compositions and source apportionment of surface soil samples collected from five sites in Shanghai, China, were successfully investigated using a laboratory-developed laser ablation single-particle aerosol mass spectrometry (LA-SPAMS) instrument combined with an adaptive resonance theory-based neural network algorithm (ART-2a) data-processing method for the first time. In total, more than 35,000 particles, ranging from 200 to 2000 nm, were sized, and around 15-20% of the particles were chemically analyzed by LA-SPAMS to generate both positive and negative mass spectra. The results show that there are significant differences in particle size distribution among the five samples, with peaks of various sizes and different profiles, while all five soil samples contain crustal elements, heavy metals, organic and inorganic components, and so forth. The chemical composition of each sample varied considerably, so different classes of SPAMS particle classes were identified, which were later grouped into seven general categories: EC-rich (containing elemental carbon), secondary components, organic nitrogen, crust, HM (containing heavy metal), PAH (containing polycyclic aromatic hydrocarbons), and NaK-rich particles, based on the dominant marked ions. The composition analysis and source apportionment showed that soil components in different areas have been affected by the local environment, such as local industrial emissions and automobile exhaust, which are usually characterized by varying degrees of mixing between the crust and environmental aerosols. In combination with the ART-2a method, LA-SPAMS enables rapid and direct analysis of soil samples based on real-time single-particle measurements, which will help in understanding the distribution, transport, and fate of the soil components, thus providing new insights into soil-quality assessment. Moreover, the established LA-SPAMS can also be practically applied to other daily inspection tasks, such as rocks, minerals, metals, ceramics, polymers, and other solid materials for ingredient analysis and quality evaluation.

Spray-inlet microwave plasma torch ionization tandem mass spectrometry for the direct detection of drug samples in liquid solutions.

RATIONALE: Drug abuse or dependence results in a series of social problems, including crime and traffic accidents. Spray-inlet microwave plasma torch tandem mass spectrometry (MPT-MS/MS) was developed and used for the direct detection of such drugs in liquid solutions. METHODS: Drug sample solutions were directly sprayed into the flame of an MPT by a sampling pump and the ions produced by Penning ionization and ion-molecule reactions were guided into a quadrupole time-of-flight (QTOF) tandem mass spectrometer for mass analysis. The MPT was operated at 40 W and 2.45 GHz in a 700 mL/min argon flow both for the inner and middle plasma. RESULTS: Intact quasi-molecular and molecular ions of various drugs were successfully characterized by spray-inlet MPT-MS/MS. The analysis of one sample was finished within 30 s. Furthermore, the method exhibited excellent efficiency, precision and sensitivity, and the limits of detection and limits of quantification of the samples in methanol were in the range of 5.25-60.0 and 17.5-200 ng g-1 , respectively. Excellent linearities with coefficients of determination (R2 ) of 0.9627-0.9980 were verified in the range 0.05-50 µg g-1 . Four different beverages purchased locally were also analyzed with spray-inlet MPT-MS/MS, and caffeine was directly determined in two of the beverages. By adding six standard drug samples to sport drinks (each drug was 1 µg g-1 ) and Chinese spirit (each drug was 0.1 µg g-1 ), all the drugs except for caffeine were detected successfully. CONCLUSIONS: This study indicates that spay-inlet MPT-MS/MS is an effective method for direct and rapid identification of drug solutions, and it has substantial potential for fast and sensitive drug residue detection.

Quantification and risk assessment of organic products resulting from non-thermal plasma removal of toluene in nitrogen.

RATIONALE: Non-thermal plasma (NTP) has proven to be an effective approach for the removal of volatile organic compounds (VOCs). However, harmful organic by-products, produced during NTP-mediated removal of VOCs, hinder practical applications of this technology. It is necessary to characterize the organic by-products to assess their health risks. METHODS: A method is proposed for analyzing and evaluating organic by-products for NTP-mediated removal of VOCs in this work. NTP generated by a coaxial dielectric barrier discharge (DBD) reactor was used for the removal of a model VOC, toluene, in nitrogen. Organic products were characterized using a real-time proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) apparatus. RESULTS: The PTR-TOF-MS apparatus has been shown to be effective for real-time high-sensitivity detection of trace VOCs. The main observed organic compounds, with concentrations on the order of ppb/ppm, were hydrogen cyanide, acetonitrile, propanenitrile, benzene, benzonitrile, and benzyl nitrile, etc. CONCLUSIONS: A health-related index (HRI) was introduced to assess the health risks associated with these organic products. The HRI was not correlated with the removal efficiency (η), with higher η possibly yielding higher HRI, associated with higher health risks. Specific input energy (SIE) was a key factor affecting the formation of the observed organic products and their HRI values. We conclude that in practical applications, SIE, HRI, and η must be balanced.

Development of an air-flow-assisted extractive electrospray ionization source for rapid analysis of phthalic acid esters in spirits.

RATIONALE: Although traditional analytical techniques like gas chromatography (GC) and GC/mass spectrometry (MS) offer satisfactory sensitivity and good reproducibility for the detection of phthalic acid esters (PAEs) in a variety of matrices, they involve laborious sample pretreatment, are time-consuming, and some are expensive and environmentally unfriendly. Furthermore, there are thousands of spirits on the market; therefore, rapid and high-throughout methods suitable for the consistent detection and quantification of PAEs in spirits are urgently required. METHODS: A new atmospheric pressure ionization method, named air-flow-assisted extractive electrospray ionization (EESI), has been developed. It is a variant on EESI and possesses the advantages of both EESI and air-flow-assisted ionization for direct analysis of samples without pretreatment. Combined with a quadrupole time-of-flight (QTOF) mass spectrometer, the method was used to directly analyze four PAEs, i.e., dipentyl phthalate, diethyl phthalate, benzyl butyl phthalate and didecyl phthalate, in spirits. RESULTS: The method exhibits excellent sensitivity, stability and convenience. Four different brands of spirits have been successfully analyzed. The total analysis time for one sample was within 1 min, and the limits of detection and limits of quantification of the samples are located in the range 0.011-0.035 and 0.038-0.087 µg g(-1), respectively. Very good linearities, with correlation coefficients of 0.9758-0.9990, are observed for the samples in the range of 0.035 to 10 µg g(-1). CONCLUSIONS: The results indicate that the air-flow-assisted EESI combined with tandem mass spectrometry is an effective method for rapid and direct determination of PAEs in spirits without sample pretreatment.

Sub-lobar resection versus lobectomy for challenging intraoperative frozen sections in lung adenocarcinoma within 3 cm.

OBJECTIVES: Intraoperative frozen section (FS) analysis is pivotal in guiding surgical interventions for early-stage lung adenocarcinoma. However, the challenge arises when distinguishing between Minimally Invasive Adenocarcinoma (MIA) and Invasive Adenocarcinoma (IAC) poses diagnostic difficulties. This study investigates the prognosis and clinicopathological characteristics of patients encountering this diagnostic challenge. METHODS: We conducted a retrospective analysis of 7082 intraoperative FSs from early-stage lung adenocarcinoma cases. The cases with pulmonary nodules within 3 cm and diagnosed as indeterminate FSs were included. We analyzed baseline data, computed tomography (CT) findings, and pathological characteristics. Prognostic data were obtained from patients with confirmed IAC diagnoses through final pathological examination. RESULTS: Out of 7082 FSs, 551 cases presented challenges in distinguishing between MIA and IAC. Upon final pathological examination, 233 cases were identified as IAC, while 314 were classified as MIA. The median invasive pathological size in the IAC group was larger than that in the MIA group (0.6 cm vs 0.3 cm). 131 cases (56.2 %) with IAC underwent lobectomy, while 102 cases (43.8 %) underwent sub-lobar resection. Among the MIA cases, 220 cases (69.8 %) underwent sub-lobar resection, while 95 cases (30.2 %) underwent lobectomy. No recurrence and disease specific death was observed during the follow-up period, regardless of surgical strategy. CONCLUSIONS: Indeterminate intraoperative FSs, posing diagnostic challenges in distinguishing between MIA and IAC. Sub-lobar resection presented the same long term survival benefit compared with the lobectomy for indeterminate lung adenocarcinoma within 3 cm during intraoperative FSs.

Gabapentin alleviated the cough hypersensitivity and neurogenic inflammation in a guinea pig model with repeated intra-esophageal acid perfusion.

OBJECTIVE: The anti-tussive effect of gabapentin and its underlying neuromodulatory mechanism were investigated via a modified guinea pig model of gastroesophageal reflux-related cough (GERC). METHODS: Intra-esophageal perfusion with hydrochloric acid (HCl) was performed every other day 12 times to establish the GERC model. High-dose gabapentin (48 mg/kg), low-dose gabapentin (8 mg/kg), or saline was orally administered for 2 weeks after modeling. Cough sensitivity, airway inflammation, lung and esophagus histology, levels of substance P (SP), and neurokinin-1 (NK1)-receptors were monitored. RESULTS: Repeated intra-esophageal acid perfusion aggravated the cough sensitivity in guinea pigs in a time-dependent manner. The number of cough events was significantly increased after 12 times HCl perfusion, and the hypersensitivity period was maintained for 2 weeks. The SP levels in BALF, trachea, lung, distal esophagus, and vagal ganglia were increased in guinea pigs receiving HCl perfusion. The intensity of cough hypersensitivity in the GERC model was significantly correlated with increased SP expression in the airways. Both high and low doses of gabapentin administration could reduce cough hypersensitivity exposed to HCl perfusion, attenuate airway inflammatory damage, and inhibit neurogenic inflammation by reducing SP expression from the airway and vagal ganglia. CONCLUSIONS: Gabapentin can desensitize the cough sensitivity in the GERC model of guinea pig. The anti-tussive effect is associated with the alleviated peripheral neurogenic inflammation as reflected in the decreased level of SP.

A guidebook of spatial transcriptomic technologies, data resources and analysis approaches.

Advances in transcriptomic technologies have deepened our understanding of the cellular gene expression programs of multicellular organisms and provided a theoretical basis for disease diagnosis and therapy. However, both bulk and single-cell RNA sequencing approaches lose the spatial context of cells within the tissue microenvironment, and the development of spatial transcriptomics has made overall bias-free access to both transcriptional information and spatial information possible. Here, we elaborate development of spatial transcriptomic technologies to help researchers select the best-suited technology for their goals and integrate the vast amounts of data to facilitate data accessibility and availability. Then, we marshal various computational approaches to analyze spatial transcriptomic data for various purposes and describe the spatial multimodal omics and its potential for application in tumor tissue. Finally, we provide a detailed discussion and outlook of the spatial transcriptomic technologies, data resources and analysis approaches to guide current and future research on spatial transcriptomics.

Design and performance of a desktop time-of-flight mass spectrometer for analyzing metal ions.

We have described a home-made desktop orthogonal-injection time-of-flight (O-ToF) mass spectrometer combining a collisional cooling system. This O-ToF consists of a simple electrospray ion source, an atmosphere-vacuum interface, an area of transmission, including a radio-frequency only quadrupole (RF- only quadrupole, RFQ) as a collisional cooling cell and an orthogonal ToF mass analyzer. In order to detect ions of small m/z value, such as small metal ions, the RFQ has been improved to weaken the mass discrimination effect against low mass ions. Metal salt solutions were used in the experiment. The system has shown a satisfactory resolving power in the spectra (m/Δm = 3500), a good mass stability, a limit of detection of 80 fg and a mass accuracy of 48 ppm. The dynamic range is found to be from 10(-8) mol L(-1) to 10(-5) mol L(-1), allowing the semi-quantitative analysis of metal ions.

Limited airway resection and reconstruction for paediatric tracheobronchial inflammatory myofibroblastic tumour.

OBJECTIVES: The paediatric tracheobronchial inflammatory myofibroblastic tumour (IMT) is a rare disease. Whether limited surgical resection is a feasible surgical approach for these patients remains controversial. The objectives of this study were to report the long-term prognosis after limited surgical resections on paediatric tracheobronchial IMT and provide a surgical management strategy for this rare disease. METHODS: Paediatric tracheobronchial IMT patients who underwent limited surgical resection from 2012 to 2020 were enrolled in this study. The clinical characteristics, course of treatment and long-term outcomes of all participants were collated. We presented the accumulated data and analysed the feasibility of limited surgical resection on the paediatric tracheobronchial IMT. RESULTS: A total of 9 children with tracheobronchial IMTs were enrolled in our study. Cough and shortness of breath were the most common symptoms. All 9 participants underwent surgical treatment, including 2 tracheal reconstructions, 4 carinal reconstructions and 3 bronchial sleeve resections. Among the participants, 6/9 (66%) were positive for the anaplastic lymphoma receptor tyrosine kinase gene in terms of immunohistochemistry. None of the participants died of short-term complications. The follow-up period was 5.4 (range, 1.1-9.3) years, during which all participants remained well. CONCLUSIONS: Limited surgical resection is preferred for paediatrics with tracheobronchial IMTs. Meanwhile, patients with complete resection have an excellent long-term prognosis.

C-dot doping for enhanced catalytic performance of TiO2/5A for toluene degradation in non-thermal plasma-catalyst system.

Non-thermal plasma (NTP) is gaining attention as a powerful tool to induce various reactions. The combination of NTP with catalysts has been successfully used to degrade volatile organic compounds (VOCs) for pollution control. In this study, a series of TiO2-C/5A catalysts, synthesized by carbon dots (C-dots) that decorate TiO2 by sol-gel and wetness impregnation methods, were incorporated with a dielectric barrier discharge (DBD) reactor in a single-stage structure to degrade toluene at atmospheric pressure and room temperature. A proton-transfer reaction mass spectrometer and a CO2 analyzer were used to monitor the concentration variations of organic by-products and CO2 online. The effects of input power, mass ratio of C-dots/TiO2 (TiO2/5A (0 wt%), TiO2-C1/5A (2.5 wt%), TiO2-C2/5A (5 wt%), TiO2-C3/5A (10 wt%)), gas flow rate, initial concentration of toluene on the toluene degradation efficiency, and CO2 selectivity were studied. The plasma-catalyst hybrid system could effectively improve the energy efficiency and reaction selectivity, attaining a maximum toluene degradation efficiency of 99.6% and CO2 selectivity of 83.0% compared to 79.5% and 37.5%, respectively, using the conventional plasma alone. Moreover, the generation of organic by-products also declined dramatically, averaging only half as much in plasma alone. The results also indicated that the appropriate amount of C-dot doping could greatly improve the catalyst efficiency in the hybrid plasma system. This is because the interaction between C-dots and TiO2 favors the formation of photoelectron holes and reduces the energy band gap and the recombination rate of photogenerated electron holes, which facilitates the generation of more active species on the catalyst surface, thereby leading to a more effective degradation reaction. These observations will provide guidance for the interaction studies between NTP and catalysts, not only for the exploration of new chemical mechanisms of aromatic compounds, but also for the screening of favorable materials for the desired reactions.

Intraoperative methods for wrapping anastomoses after airway reconstruction: a case series.

Background: Anastomosis management is the main challenge of airway resection and reconstruction, and postoperative anastomotic complications, including ischemia, stenosis, dehiscence, and separation may lead to severe outcomes and a poor prognosis. The anastomotic buttress is vital in airway reconstruction, but the selection of surgical buttress and reinforcement remains controversial. We aimed to demonstrate and evaluate the buttress options of anastomosis, including their preoperative characteristics, the intraoperative process, and the incidence of postoperative complications to help address the controversy regarding anastomosis management. Methods: This retrospective study was conducted at a single institution. Patients who underwent airway reconstruction with anastomotic wrapping from Jan. 2019 to Sep. 2021 were enrolled in this study and preoperative characteristics and operational features were collected. All patients were carefully followed up by telephone and outpatient. Their postoperative complications and postoperative status after 6 months were recorded. The surgical procedures and clinical characteristics of the buttress options of anastomosis were assessed. Results: A total of 62 patients undergoing either cervical tracheal, thoracic tracheal, carinal, or secondary carinal and main bronchus resection and reconstruction were evaluated. The anastomotic buttress used included mediastinal pleural flap (24/62, 38.7%), anterior cervical muscle (14/62, 22.6%), sternocleidomastoid (2/62, 3.2%), thymus flap (12/62, 19.4%), intercostal muscle flap (2/62, 3.2%), biological patch (2/62, 3.2%), prepericardial fat (1/62, 1.6%), thyroid gland (1/62, 1.6%), pectoralis major flap (2/62, 3.2%), and omental flap (2/62, 3.2%). All procedures produced satisfactory results without short-term anastomotic complications. A follow-up for 6 months was conducted and all patients were alive postoperatively. Tracheomalacia stenosis postoperatively occurred in 3 patients and they were subsequently treated with an endotracheal stent. One patient had tumor recurrence 3 months after surgery and received adjuvant chemotherapy. Conclusions: Various anastomotic wrapping materials are used in airway reconstruction. Different utilizations of buttress are selected according to the anatomic characteristics and the reconstruction method used. This study indicated that appropriate surgical buttresses for wrapping anastomoses are legitimate alternatives to reduce the risk of anastomotic complications.

Artificial intelligence assisted display in thoracic surgery: development and possibilities.

In this golden age of rapid development of artificial intelligence (AI), researchers and surgeons realized that AI could contribute to healthcare in all aspects, especially in surgery. The popularity of low-dose computed tomography (LDCT) and the improvement of the video-assisted thoracoscopic surgery (VATS) not only bring opportunities for thoracic surgery but also bring challenges on the way forward. Preoperatively localizing lung nodules precisely, intraoperatively identifying anatomical structures accurately, and avoiding complications requires a visual display of individuals' specific anatomy for surgical simulation and assistance. With the advance of AI-assisted display technologies, including 3D reconstruction/3D printing, virtual reality (VR), augmented reality (AR), and mixed reality (MR), computer tomography (CT) imaging in thoracic surgery has been fully utilized for transforming 2D images to 3D model, which facilitates surgical teaching, planning, and simulation. AI-assisted display based on surgical videos is a new surgical application, which is still in its infancy. Notably, it has potential applications in thoracic surgery education, surgical quality evaluation, intraoperative assistance, and postoperative analysis. In this review, we illustrated the current AI-assisted display applications based on CT in thoracic surgery; focused on the emerging AI applications in thoracic surgery based on surgical videos by reviewing its relevant researches in other surgical fields and anticipate its potential development in thoracic surgery.

Limited Clinical Utility of Lipid-Laden Macrophage Index of Induced Sputum in Predicting Gastroesophageal Reflux-Related Cough.

Gastroesophageal reflux disease (GERD) is a common cause of chronic cough (CC). However, the diagnosis of GERD associated with CC based on 24-hour esophageal pH-monitoring or favorable response to empirical anti-reflux trials is invasive and time-consuming. Lipid-laden macrophages (LLMs) are supposed to be a biomarker for micro-aspiration of gastric content in the respiratory tract. This study was conducted to collect LLMs by the sputum induction technique and observe the relationship among the amount of LLMs, cough severity, parameters of 24-hour esophageal pH-monitoring and therapeutic response. The 24-hour esophageal pH-monitoring and sputum induction were performed on 57 patients with suspected GERD associated with CC. Thirty-four patients were followed up after empirical anti-reflux trials of 8 weeks to record the therapeutic response. Lipid-laden macrophage index (LLMI), a semiquantitative counting of LLMs, showed no significant correlation with the values of 24-hour esophageal pH monitoring at the proximal or remote electrode. No difference in LLMI or DeMeester score, as well as cough symptom association probability, were found between the responders and the non-responders. Reflux symptoms were more common in the responders (50%) compared to the non-responders (6%) (P < 0.05). Our study suggests that LLMI shows limited utility in clinically diagnosing GERD associated with CC as an underlying etiology or in predicting response to anti-reflux therapy. Anti-reflux therapy is more effective for CC patients with reflux symptoms than for those without.

Development of a new atmospheric pressure plasmaspray ionization for ambient mass spectrometry.

A new atmospheric pressure ionization method, plasmaspray ionization, termed as PSI, was developed to be an alternative ambient ion source for mass spectrometry. It comprises a plasma jet device and a sample spray part. While the nonthermal plasma jet strikes the surface of stainless steel tube out of the spray capillary, the sprayed sample will be ionized with the assistant of auxiliary gas. Although PSI is a little bit more complex than electrospray ionization (ESI) in instrument, it shows both better linearity and higher sensitivity for organic compounds. For protein samples, it presents wider distributions of multiply charged ions and higher mass resolution without sacrificing any sensitivity. For the mechanism of PSI, the charge build-up process on the tip of capillary should play a key role for the ion formation, and the stimulated pulsed voltage on the flow tube will promote the ion aggregation speed until the charge density is high enough. PSI source contains the features of plasma ionization and ESI and can be considered as a novel combo bridging these techniques. These results reflect that this method of PSI can be applied and further developed as a versatile new ion source for a wild range of organic and biological samples.

Smog chamber study of the effects of NOx and NH3 on the formation of secondary organic aerosols and optical properties from photo-oxidation of toluene.

Secondary organic aerosols (SOAs) have been receiving significant attention because of their significant impacts on air quality and human health. In this study, the influences of nitrogen oxides (NOx) and ammonia (NH3) on SOA formation from photooxidation of toluene was investigated in the Shanghai university smog chamber. The chemical and physical characteristics of gas-phase products and SOAs from toluene photo-oxidation were characterized using laboratory-developed single photon ionization time-of-flight mass spectrometry, single particle aerosol mass spectrometry, and cavity ring-down aerosol extinction albedo spectroscopy instruments. It was observed that increasing the initial nitrogen oxides ([NOx]0) under low-[NOx]0 conditions enhanced the SOA yield, while increasing [NOx]0 under high-[NOx]0 conditions suppressed the SOA yield. After adding NH3, the number concentration, average SOA diameter, and extinction and scattering coefficients showed an immediate and rapid increase due to the formation of significant amounts of condensable ammonium nitrate and nitrogen-containing (NOC) compounds. Moreover, a simplified reaction mechanism for the photooxidation of toluene initiated by the hydroxyl radical (OH) was believed to follow two reaction channels: minor H abstraction, and major OH addition, which continuously induced the subsequent reactions. The results of this study presented rapid analytical method for the joint use of a smog chamber with on-line analytical instruments to immediately characterize the effects of SOA formation, which will help in understanding the new particle formation and particle growth, and thus provides a new insight for in-depth understanding of the haze pollution in China.

Detection of the effects of triclosan (TCS) on the metabolism of VOCs in HepG2 cells by SPI-TOFMS.

Volatile organic compounds (VOCs) emitted by organisms and cell metabolism have demonstrated great physiological and pathological values. At present, there is a great interest in the study of volatile metabolome to determine whether VOCs can serve as potential diagnostic biomarkers. In view of the sensitivity of VOCs to physiological changes, the aim of this study was to investigate alterations in VOC profiles in the in vitro headspace of HepG2 cells after exposure to triclosan (TCS). Since the in vivo biological effects of TCS are clearly defined, several TCS-related VOCs may potentially be traced back to common cellular processes. In this study, HepG2 cells were cultured in TCS-containing medium for 2 h, and the emitted VOCs in the headspace of the culture flask were detected using a single photon ionization time-of-flight mass spectrometry instrument. The control group and the TCS-treated group could be well separated by differential VOC profiles, which were related to the physiological states of the HepG2 cells. Compared to the control group, eleven and ten specific VOCs were identified in the 20 µm and 50 µm TCS-treated groups, respectively. Among them, five specific VOCs (m/z 62, 64, 70, 121 and 146) were commonly observed in these two TCS-treated groups. These results indicate that TCS can cause changes in cellular metabolic VOCs, and different concentrations of TCS lead to different VOCs profiles. Based on the findings of the study, the detection of VOCs in cell metabolism can be used as an auxiliary tool to explore the mechanism of drug action, and also as an exploratory method to determine whether drugs play a role in disease treatment.

Reaction kinetic study of nonthermal plasma continuous degradation of acetone in a closed-loop reactor.

Nonthermal plasma (NTP) degradation has been shown to be a promising method for volatile organic compounds (VOCs) removal from air. However, there have been few studies on the degradation of indoor VOCs using NTP, and even less on their reaction kinetics. In this study, NTP degradation of acetone, a representative of oxygenated VOCs, in a closed-loop reactor operating in recirculation mode was investigated. Acetone and organic by-products were characterized in real-time by proton transfer reaction time-of-flight mass spectrometry. The results showed that approximately 85.7% of the acetone degraded within 7.5 h with dielectric barrier discharge treatment at 4.3 W. Methanol, acetaldehyde, formic acid, and acetic acid were observed to be the main organic byproducts with concentrations time-dependent on the order of ppb/ppm. The concentrations of the inorganic by-products O3 and NO2 are also time-dependent and can decrease to nearly 0 after a sufficient degradation time. Based on the concentration measurement in real-time, several rate laws were used to fit the concentration variations of acetone and the organic by-products, and it was observed that they strictly followed the simple kinetic reaction rate laws: acetone followed the first-order rate law, and formic acid formation followed the one-half-order rate law, etc. This study provides a good example of characterizing NTP removal of VOCs in airtight spaces and has important theoretical and practical significance in designing a better NTP device, predicting NTP degradation reaction rate, and accelerating the practical application of NTP technology for indoor air treatment.

Real-time monitoring and quantification of organic by-products and mechanism study of acetone decomposition in a dielectric barrier discharge reactor.

Non-thermal plasma (NTP) degradation of low-concentration acetone was investigated in a cylindrical dielectric barrier discharge reactor. The effects of oxygen content and flow rate on the removal efficiency at various discharge powers were examined in real-time. The acetone removal efficiency decreases drastically and then remains stable or increases gradually as the O2 content increases from 0 to 25%, and further to 50%. The organic by-products were characterized and quantified using a real-time proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) instrument. The observed organic compounds, with concentrations about ppbv/ppmv by volume, were mainly formaldehyde, methanol, ketene, acetaldehyde, formic acid, acetone, and acetic acid. The discharge power was a critical factor affecting the concentration of the organic by-products and the selectivity toward CO2. The mechanism study based on the by-product monitor in real-time showed that acetone firstly fragments into methyl radicals, acetyl radicals, and H; then, the methyl and acetyl radicals are oxidized by O or OH radicals into acetaldehyde, methanol, and other compounds. It seems that acetaldehyde could be an intermediate in acetone decomposition. Firstly, most of the acetone molecules were decomposed into acetaldehyde molecules; then, the acetaldehyde molecules continued to be decomposed and oxidized into other compounds, such as acetic acid and formaldehyde. These investigations not only proposed a detail decomposition mechanism for acetone in dielectric barrier discharge reactor, but also provided a potential way to analyze and evaluate the practicability of NTP removal of VOCs.

A homemade high-resolution orthogonal-injection time-of-flight mass spectrometer with a heated capillary inlet.

We describe a homemade high-resolution orthogonal-injection time-of-flight (O-TOF) mass spectrometer combing a heated capillary inlet. The O-TOF uses a heated capillary tube combined with a radio-frequency only quadrupole (rf-only quadrupole) as an interface to help the ion transmission from the atmospheric pressure to the low-pressure regions. The principle, configuration of the O-TOF, and the performance of the instrument are introduced in this paper. With electrospray ion source, the performances of the mass resolution, the sensitivity, the mass range, and the mass accuracy are described. We also include our results obtained by coupling atmospheric pressure matrix-assisted laser deporption ionization with this instrument.

Direct determination of trace phthalate esters in alcoholic spirits by spray-inlet microwave plasma torch ionization tandem mass spectrometry.

A direct analytical method based on spray-inlet microwave plasma torch tandem mass spectrometry was applied to simultaneously determine 4 phthalate esters (PAEs), namely, benzyl butyl phthalate, diethyl phthalate, dipentyl phthalate, and dodecyl phthalate with extremely high sensitivity in spirits without sample treatment. Among the 4 brands of spirit products, 3 kinds of PAE compounds were directly determined at very low concentrations from 1.30 to 114 ng·g-1 . Compared with other online and off-line methods, the spray-inlet microwave plasma torch tandem mass spectrometry technique is extremely simple, rapid, sensitive, and high efficient, providing an ideal screening tool for PAEs in spirits.