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This paper introduced a homemade high-performance proton transfer reaction time-of-fight mass spectrometer (PTR-TOF MS), which can be used for real-time online analysis and monitoring of complex organic gas mixtures. Proton transfer reaction ionization is one of the typical methods of “soft” ionization techniques, which generally takes water and hydronium ions as parent ions, and the objects which have higher proton affinity than water can be ionized. By integrating an orthogonal-injection reflectron time-of-flight mass analyzer and a micro-channel plate detector, the instrument’s resolution and sensitivity are significantly enhanced，with the characteristics of high sensitivity, a wide mass detection range, a low detection limit, a wide linear range and little sample pretreatment. The system is mainly composed of hollow cathode discharge ion source, proton transfer reaction tube, high efficiency ion transport region and high-performance time-of-flight mass analyzer. To reduce ion loss during transmission, improve system performance and ensure the stability of vacuum at all levels, the system adopts a four-stages of differential vacuum design, with the first stage being the proton transfer reaction tube, the second stage being the radio frequency quadrupole ion transport region, the third stage being the direct current quadrupole ion transport region, and the fourth stage being the time-of-flight mass analyzer. Based on the proton affinity of the reaction reagent ions, the system can analyze the majority of VOCs while excluding interference from air components. Experimental tests showed that the system’s resolution (full width half maximum, FWHM) is better than 2 069 (for toluene), with the detection limit of 0.36 μg/m3, a linear range of 4 orders of magnitude, and a linear correlation coefficient (R2) of 0.991. The development of this system provides a new method for online rapid analysis of VOCs in environmental monitoring, industrial processes, and biomedicine, accelerating the technical development of PTR-TOFMS domestically and narrowing the gap with the international advanced level.

Atmospheric organic aerosols consist of both gas-phase organic compounds and particle-phase organic compounds. The components of aerosol particles (solid or liquid droplets) can undergo exchange or chemical reactions with gas-phase components, influencing atmospheric physical and chemical processes and potentially impacting atmospheric environment, climate, and human health. Methods for detecting organic compounds in aerosol particle phase are classified into offline and online detection. Offline detection methods involve collecting aerosol samples for analysis using chromatography-mass spectrometry, which is time-consuming and limited sensitivity. Online detection methods involve enriching aerosols through aerodynamic lens and then detecting them using laser ablation or electron impact ionization techniques. However, these methods usually generate a large number of ion fragments, making mass spectrum analysis difficult. Therefore, it is necessary to develop an online detection method for aerosol particle-phase organic compounds with soft ionization and high sampling efficiency. In the present work, a set of aerodynamic lens sampling systems was designed and developed for online detection and analysis of organic compounds in aerosol particle phase. This sampling system consists of a gas-phase stripping module for removing gas-phase organic compounds, an aerodynamic lens module for particle focusing and enrichment, and a thermal desorption module for extracting particle-phase organic compounds. The efficiency of gas-phase organic compound removal and the particle transmission rate of the gas-phase stripping module were firstly investigated. The results showed that gas-phase stripping module achieves a removal efficiency of 98.89% for gas-phase organic compounds, and the particle transmission rate ranges from 75.16% to 91.15% for particles with the diameters between 295 and 375 nm. Subsequently, the effectiveness of the aerodynamic lens was studied through theoretical simulations. The simulation results indicated that the transmission rate of particles in the diameters of 0.36-6.0 μm is above 90% in the designed aerodynamic lens. Finally, The designed aerodynamic lens sampling system with a homemade proton transfer reaction mass spectrometer (PTR-MS) was integrated to develop an aerodynamic lens-PTR-MS device. This device was tested by detecting simulated aerosol samples containing reaction products of α-pinene and ozone. The mass spectrometry results demonstrated that the intensity changes of the examined ten ions are closely related to the presence of α-pinene, confirming that the device can achieve online detection of organic compounds in aerosols ranging from submicron to several micrometers.

The objective of this paper is to evaluate the physicochemical properties of electron transfer reaction of semicarbazide and tetrakis (2, 2'-bipyridine)-µ-oxodiiron (III) complex [Fe2O4+] in aqueous acidic media at [H+] = 0.001mol dm-3, µ = 0.3 mol dm-3(NaCl), T = 27 ± 0.5, at max = 520 nm by spectrophotometric method. In the course of the reaction a mole of semicarbazide was consumed by a mole of [Fe2O4+]. The order of reaction is unity dependent on [Fe2O4+] and zero order dependent on semicabazide and is not H+ and µ dependent. Addition of cations and anions did not affect the reaction. There was no intermediate formation when a partially reacted reaction mixture and the solution of oxidant were respectively scanned within a wavelength of 400 - 700nm. Absence of spectroscopic evidence of intermediate complex formation suggests that the reaction proceeds by the outer-sphere mechanistic pathway with ion pair character. [ABSTRACT FROM AUTHOR]

The physicochemical properties of molecules can be modulated through polariton formation under strong electromagnetic confinement. Here, we discuss the possibility of exploiting this phenomenon to increase the electron transfer rate at an electrode–electrolyte interface. Electron transfer theory under strong electromagnetic confinement can be extended to the electrode–electrolyte interface, and single-electron transfer reactions can be simulated using Gerischer's theory. Although single electron transfer in free space is well described using Marcus theory, the vacuum electric field can facilitate an additional electron transfer pathway via virtual photon excitation under cavity strong coupling conditions. Therefore, this binary reaction pathway for single electron transfer can yield a quasi-two-particle electron transfer process. This quantum behavior can dominate when the mode volume is small and when there are a large number of molecules in the vacuum electric field. Exploitation of polaritons in single electron transfer reactions can lead to enhanced electrochemical energy conversion systems. [ABSTRACT FROM AUTHOR]

The photochemistry of carbonyl compounds significantly influences tropospheric chemical composition by altering the local oxidative capacity; free radical abundance in the upper troposphere; and formation of ozone, peroxycarboxylic nitric anhydride (PAN), and secondary organic aerosol particles. Carbonyl compounds can be emitted directly from the biosphere into the atmosphere and are formed through photochemical degradation of various precursor compounds. Aldehydes have atmospheric lifetimes of hours to days, whereas ketones persist for up to several weeks. While standard operating conditions for a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) using H3O+ ions are unable to separate aldehydes and ketones, the use of NO+ reagent ions allows for the differential detection of isomeric carbonyl compounds with a high temporal resolution. Here we study the temporal (24 h) and vertical (80–325 m) variability of individual carbonyl compounds in the Amazon rainforest atmosphere with respect to their rainforest-specific sources and sinks. We found strong sources of ketones within or just above the canopy (acetone, methyl ethyl ketone (MEK), and C5 ketones). A common feature of the carbonyls was nocturnal deposition observed by loss rates, most likely since oxidized volatile organic compounds are rapidly metabolized and utilized by the biosphere. With NO+ chemical ionization, we show that the dominant carbonyl species include acetone and propanal, which are present at a ratio of 1 : 10 in the wet-to-dry transition season and 1 : 20 in the dry season.

Volatile organic compounds (VOCs) are one of significant contributors to air pollution and have profound effects on human health and the environment. This study introduces a detailed analysis of VOC emissions from various industries within an industrial complex using a high-resolution measurement instrument. This study aimed to identify the VOC profiles and their concentrations across 12 industries. Sampling was conducted across 99 facilities in an industrial complex in South Korea, and VOC analysis was performed based on measurement data using a Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS). The results indicated that the emission of oxygenated VOCs (OVOCs) was dominant in most industries. Aromatic hydrocarbons were also dominant in most industries, except in screen printing (SP), lubricating oil and grease manufacturing (LOG), and industrial laundry services (ILS) industries. Chlorinated VOCs (Cl-VOCs) showed a relatively higher level in the metal plating (MP) industry than those in other industries and nitrogen-containing VOCs (N-VOCs) showed high levels in general paints and similar product manufacturing (PNT), MP, and ILS industries, respectively. The gravure printing industry was identified as the highest emitter of VOCs, with the highest daily emissions reaching 5934 mg day−1, primarily consisting of ethyl acetate, toluene, butyl acetate, and propene. The findings suggest that the VOC emissions from the gravure printing and plastic synthetic leather industries should be primarily reduced, and it would be the most cost-effective approach to improving air quality. This study can provide the fundamental data for developing effective reduction technologies and policies of VOC, ultimately contributing to enhanced atmospheric models and regulatory measures.

The objective of this paper is to evaluate the physicochemical properties of electron transfer reaction of semicarbazide and tetrakis (2, 2’-bipyridine)-μ-oxodiiron (III) complex [Fe2O4+] in aqueous acidic media at [H+] = 0.001mol dm-3, µ = 0.3 mol dm-3(NaCl), T = 27 ± 0.5, at λmax = 520 nm by spectrophotometric method. In the course of the reaction a mole of semicarbazide was consumed by a mole of [Fe2O4+]. The order of reaction is unity dependent on [Fe2O4+] and zero order dependent on semicabazide and is not H+ and µ dependent. Addition of cations and anions did not affect the reaction. There was no intermediate formation when a partially reacted reaction mixture and the solution of oxidant were respectively scanned within a wavelength of 400 -700nm. Absence of spectroscopic evidence of intermediate complex formation suggests that the reaction proceeds by the outer-sphere mechanistic pathway with ion pair character.

Studies of volatile organic compounds (VOCs) emitted from the bottom sediments of three Pomeranian lakes in Poland: Łazienkowskie, Rychnowskie, and Jeleń were conducted. All three lakes are subject to anthropogenic pressure but to varying degrees. In 2021, bottom sediment samples were taken from the lakes studied and an analysis of the emission of 20 volatile organic compounds was carried out using a proton transfer reaction mass spectrometer (PTR-MS). Concentrations in emissions from the bottom sediments of VOCs with the following mass–charge ratio (m/z) were analyzed: 57, 61, 63, 69, 75, 81, 83, 85, 87, 95, 97, 99, 101, 109, 111, 127, 129, 137, 149, and 157. The obtained data were analyzed by performing statistical tests and multivariate cluster and PCA analysis. The analysis shows that the lowest concentrations of VOCs were observed from bottom sediments in Lake Jeleń, which is subject to the lowest anthropopressure among the studied lakes. The analysis shows that the lowest concentrations of VOCs were observed from bottom sediments in Lake Jeleń, which is subject to lower anthropopressure among the studied lakes. With the help of cluster analysis, it was possible to collect data on the VOC concentrations into clusters, which resulted in demonstrating similarities between Łazienkowskie and Rychnowskie lakes—lakes connected by an isthmus, and the different characteristics of Lake Jeleń. PCA analysis leads to similar observations. The tested m/z VOCs can be identified using additional analytical methods.

Condensed particulate polycyclic aromatic hydrocarbons (PAHs) are a group of toxic organic compounds that are produced by the incomplete combustion of organic material, for example, via biomass burning or traffic emissions. Even at low long-term exposure levels, such as 1 ng m−3 of benzo(a)pyrene, PAHs are recognized to be detrimental to human health. Therefore, a quantitative characterization of PAHs at sub-nanogram-per-cubic-meter levels is important to examine precise long-term exposure. A new ultrasensitive generation of proton transfer reaction mass spectrometry (PTR-MS) instruments coupled to the CHARON particle inlet are capable of quantitatively detecting this toxic class of compounds at a molecular composition level while also offering a high temporal resolution of < 1 min and sub-nanogram-per-cubic-meter limits of detection. To demonstrate the capabilities of this new CHARON FUSION PTR-TOF 10k instrument, we present a thorough characterization of summertime ambient condensed PAHs in Innsbruck, Austria. With a mass resolution of > 14 000 (m Δm−1 at full width at half maximum) and sensitivities of up to 40 cps ng−1 m3 (where cps represents counts per second), a series of nine condensed PAHs of four (C16H10) to six aromatic rings (C26H16) are identified among a plethora of organic compounds in ambient organic aerosol. With 1 min limits of detection between 19 and 46 pg m−3, quantitative time series of these PAHs at the lowermost mass concentrations are determined. To understand the sources and processes associated with these condensed summertime PAHs in greater detail, a matrix factorization including the ∼ 4000 ionic signals detected by the CHARON FUSION PTR-TOF 10k is performed, representing the vast majority of the mass concentration of ambient organic aerosol. A total of 10 factors and their corresponding time series can be identified. Known tracer compounds like levoglucosan, pinonic acid or nicotine consequently allow the assignment to individual organic aerosol sources and physicochemical processes. PAH emissions from traffic are found to be minor contributors during this summertime sampling period. The highest concentrations of PAHs are identified in a mixed aged oxygenated organic aerosol, followed by a biomass burning and a cigarette smoke organic aerosol.

We present a theory of the effect of quantum tunneling on the basic parameter that characterizes the effect of pressure on the rate constant of chemical reactions in a dense phase, the activation volume. This theory results in combining, on the one hand, the extreme pressure polarizable continuum model, a quantum chemical method to describe the effect of pressure on the reaction energy profile in a dense medium, and, on the other hand, the semiclassical version of the transition state theory, which includes the effect of quantum tunneling through a transmission coefficient. The theory has been applied to the study of the activation volume of the model reaction of hydrogen transfer between methyl radical and methane, including the primary isotope substitution of hydrogen with deuterium (H/D). The analysis of the numerical results offers, for the first time, a clear insight into the effect of quantum tunneling on the activation volume for this hydrogen transfer reaction: this effect results from the different influences that pressure has on the competing thermal and tunneling reaction mechanisms. Furthermore, the computed kinetic isotope effect (H/D) on the activation volume for this model hydrogen transfer correlates well with the experimental data for more complex hydrogen transfer reactions. [ABSTRACT FROM AUTHOR]

Kaffir lime juice, often treated as production waste, can be a good source of terpenes. These compounds undergo various decomposition processes under the influence of external factors, especially during transportation and storage. In this paper, it was possible to monitor changes in the terpene profile of kaffir lime juice under different storage conditions, namely, 4 °C, 20 °C, and 35 °C. The identification of key decomposition products was achieved using gas chromatography–mass spectrometry (GC–MS) and a data mining protocol. It was followed by tracing those products in different storage conditions using a high-throughput proton transfer reaction mass spectrometry (PTR–MS) approach. Based on our findings, degradation pathways were presented, showing that the main products resulting from storage are p-cymene, p-cymenene, terpinene-4-ol, and α-terpineol. It was shown that conversion to p-cymenene occurs after 5 days of storage. Terpinene-4-ol and α-terpineol were found to be the final products of the conversion at all temperatures. Changes in the composition of terpenes are important from the point of view of their bioactive properties.

Volatile organic compounds (VOCs) affect secondary pollutant formation via active chemistry. Proton-transfer-reaction mass spectrometry (PTR-MS) is one of the most important techniques to study the highly variable spatial and temporal characteristics of VOCs. The response of protonated, adduct, and fragmented ions in PTR-MS in changing instrument settings and varying relative humidity (RH) requires rigorous characterization. Herein, we present dedicatedly designed laboratory experiments conducted to investigate the response of these ions for 21 VOCs, including 12 oxygenated VOCs and 2 nitriles, using the recently developed Vocus PTR-MS. Our results show that the focusing ion–molecule reactor (FIMR) axial voltage increases sensitivity by 3 to 4 orders of magnitude but does not significantly change the fractions of protonated ions. Reducing the FIMR pressure, however, substantially increases fragmentation. Applying a high radio frequency (RF) amplitude radially to the FIMR can enhance sensitivity by 1 to 2 orders of magnitude without affecting the protonated ion fractions. The change in big segmented quadrupole (BSQ) amplitude mainly affects sensitivity and protonated ion fraction by modifying ion transmission. The relationship between sensitivity and proton-transfer reaction rate constant is complicated by the influences from both ion transmission and protonated ion fraction. The protonated ions of most VOCs studied (19 out of 21) show less than 15 % variations in sensitivity as RH increases from ∼ 5% to ∼ 85 %, except for some long-chain aldehydes which show a positive RH variation of up to 30 %. Our results suggest that the Vocus PTR-MS can reliably quantify the majority of VOCs under ambient conditions with varying RH. However, caution is advised for small oxygenates such as formaldehyde and methanol due to their low sensitivity and for long-chain aldehydes due to their slight RH dependence and fragmentation.

The prerequisite for electrocatalytic hydrogenation reactions (EHRs) is H2O splitting to form surface hydrogen species (*H), which occupy catalytic sites and lead to mismatched coverage of *H and reactants, resulting in unsatisfactory activity and selectivity. Thus, modulating the splitting pathway of H2O is significant for optimizing the EHR process. Herein, a Cu−Ag alloy with a superlattice structure of staggered‐ordered Cu and Ag is theoretically predicted and experimentally proven to undergo a pathway for H2O splitting called the hydrogen transfer reaction (HTR) in the water layer, which involves the formation of *H, the capture of *H by a water cluster to form H*(H2O)x and subsequent hydrogenation reactions by H*(H2O)x. Taking acetylene hydrogenation as a model case, the as‐proposed HTR pathway could lead to a relaxation hydrogenation process to modulate the matching degree of C2H2 and *H, thus enabling a 91.2 % C2H4 Faradaic efficiency at a partial current density of 0.38 A cm−2, greatly outperforming its counterpart without a superlattice structure. [ABSTRACT FROM AUTHOR]