The determination of volatile organic compounds (VOCs) in various gases, including atmospheric and exhaled air, is necessary to solve a wide range of environmental problems and monitore gas composition, and is increasingly used for diagnosing a variety of diseases. Recently, methods of soft ionization with minimal fragmentation of components have been rapidly developed. Our research group is developing an approach to the direct analysis of mixtures of volatile organic compounds by time-of-flight mass spectrometry with a pulsed glow discharge. Previously, the effects of various gases and gas mixtures on ionization processes have not been compared. This work presents a study of the mechanisms of VOC ionization in argon, nitrogen, and air. Toluene, p-xylene, chlorobenzene, and 1,2,4-trimethylbenzene were selected as model VOCs. The parameters of the microsecond pulsed glow discharge (pulse period and duration, ejection pulse delay, pressure in the discharge cell) have been optimized for each compound and a gas mixture of several volatile organic compounds. The predominant ionization mechanisms are the formation of molecular ions of VOCs through Penning ionization and proton transfer reactions, with their effects varying depending on the gas. The use of argon, even with a small addition of water, leads to the predominance of the proton transfer reaction, while in nitrogen and air mixtures, Penning ionization prevails. Under the optimized conditions in air, for which the highest VOC intensities were attained, the developed approach for analyzing exhaled breaths and samples of atmospheric air was tested.

Hexanal detection is essential for real-time monitoring of oil oxidation stability and evaluating health impact. Nevertheless, accurately monitoring hexanal levels in the presence of other volatile organic compounds (VOCs) remains a significant challenge. In this article, we present an In2O3/SnO2 composite-based electrochemical gas sensor that offers excellent selectivity for hexanal over other tested VOCs, such as styrene, acetone, and n-hexane, and featured a remarkably low detection limit of approximately 50 parts per billion (ppb). In addition, a gas sensing device that integrated the aforementioned electrochemical hexanal sensor with blockchain technology was developed to facilitate remote monitoring of hexanal variations. In particular, shuffling technology and digital signatures were utilized to bolster the security of data transmission and access. It turns out that the developed sensing device demonstrated impressive performance in both sensing accuracy and data security, highlighting its potential as a promising solution for remote hexanal monitoring.

This article describes the key achievements over the past 10 years in the microsecond pulsed glow discharge mass spectrometry applied to the analysis of solids and gaseous mixtures. The solid-state analysis allows studying solid materials with different conductivities, including direct simultaneous quantitation of light elements with high ionization energy (N, O, F, Cl, etc.), heavy elements (U, Th, etc.), and isotope analysis. Dielectric materials analysis is considered in details with special emphasis on sample preparation approaches. Particular attention is focused on a new application of the technique for detection of volatile organic and inorganic compounds in gas mixtures (model gas mixtures, ambient air and exhaled air). This approach has prospects for solving medical and environmental problems as well as for process gas monitoring. Several applications (He determination in deuterium, detection of VOCs, Xe and other inorganic compounds in air) are presented as examples. Using the high resolution (6000 for Pb, m/z 208) of Lumas PGD-301 time-of-flight mass spectrometer helps to eliminate most of the interferences and thereby improves the analytical performance. Combination of high energy electron ionization with soft Penning and other ionization mechanisms allows to detect almost all known elements and molecules.

The application of electronic nose system as an instrument for exhaled air analysis for diagnosing various diseases (lung cancer, etc.) is one of the most rapidly developing areas of predictive medicine. However, a significant disadvantage of such systems is difficulty in production of identical multi-sensor systems because the sensors of the same type are not identical, that degrades the predictive ability. To solve this problem calibration transfer methods are used.This paper analyzes currently applied calibration transfer methods. A new approach to evaluate the effectiveness of calibration transfer methods for two multi-sensor systems is proposed and implemented. One- and three-component gas mixtures are taken for the analysis. In this work, four methods are used to adjust the sensor responses: UDS, UDSwoi, DS-L1R and DS-PLS2. Applicability of one-factor standardization methods (UDS and UDSwoi) is shown on the classification tasks: multi-class classification task of one-component gas mixtures and binary classification task of three-component gas mixtures. Multi-class classification of model one-component gas mixtures for UDS, UDSwoi with 4 calibration transfer samples provided the classification accuracy of 0.985 and 0.990, respectively. The binary classification of two three-component mixtures with different ratios of three VOCs within the 20% discrepancy limits, UDS, UDSwoi and DS-PLS2 achieved an error-free accuracy of 1.000.

The real-time monitoring of food freshness in refrigerators is of significant importance in detecting potential food spoiling and preventing serious health issues. One method that is commonly reported and has received substantial attention is the discrimination of food freshness via the tracking of volatile molecules. Nevertheless, the ambient environment of low temperature (normally below 4 °C) and high humidity (90% R.H.), as well as poor selectivity in sensing gas species remain the challenge. In this research, an integrated smart gas-tracking device is designed and fabricated. By applying pump voltage on the yttria-stabilized zirconia (YSZ) membrane, the oxygen concentration in the testing chamber can be manually tailored. Due to the working principle of the sensor following the mixed potential behavior, distinct differences in sensitivity and selectivity are observed for the sensor that operated at different oxygen concentrations. Typically, the sensor gives satisfactory selectivity to H2S, NH3, and C2H5OH at the oxygen concentrations of 10%, 30%, and 40%, respectively. In addition, an acceptable response/recovery rate (within 24 s) is also confirmed. Finally, a refrigerator prototype that includes the smart gas sensor is built, and satisfactory performance in discriminating food freshness status of fresh or semi-fresh is verified for the proposed refrigerator prototype. In conclusion, these aforementioned promising results suggest that the proposed integrated smart gas sensor could be a potential candidate for alarming food spoilage.

Metal-organic frameworks (MOFs) have attracted widespread interest due to their unique and unprecedented advantages in microstructures and properties. Besides, surface-enhanced Raman scattering (SERS) technology has also rapidly developed into a powerful fingerprint spectroscopic technique that can provide rapid, non-invasive, non-destructive, and ultra-sensitive detection, even down to single molecular level. Consequently, a considerable amount of researchers combined MOFs with the SERS technique to further improve the sensing performance and broaden the applications of SERS substrates. Herein, representative synthesis strategies of MOFs to fabricate SERS-active substrates are summarized and their applications in ultra-sensitive biomedical trace detection are also reviewed. Besides, relative barriers, advantages, disadvantages, future trends, and prospects are particularly discussed to give guidance to relevant researchers.

Glow discharge (GD) source gained an increased level of attention in relation to the analysis of volatile organic compounds (VOCs) since past work showed that this soft ionization method allowed direct analysis of VOCs with minimal fragmentation, however, the issue of fragmentation was not previously studied in detail. The aim of the present work was to investigate the effect of discharge conditions on VOC fragmentation in the system consisting of the cell with pulsed glow discharge and a time-of-flight mass spectrometer. Ionization of VOCs of different classes (hydrocarbons, alcohols, esters, and carboxylic acids) was investigated. A copper cathode with flat geometry was used. VOCs were ionized in the afterglow of short pulse glow discharge in the air. The use of discharge afterglow significantly reduces or eliminates the effects of ionization mechanisms other than Penning process, in particular, electron ionization. This significantly reduced VOC fragmentation and provided rather low limits of detection. Specific cluster formation was observed for alcohols and esters, which may facilitate their identification.

The determination of nonmetals, first of all, the most electronegative ones-nitrogen, oxygen, fluorine, chlorine, and bromine, poses the highest challenge for element analysis. These elements are characterized by high reactivity, volatility, high ionization energy, and the absence of intensive spectral lines in the optical spectral range. Conventional techniques of their quantification include considerable "wet chemistry" stages so the application of these techniques for the solid sample is highly laborious and prone to uncontrollable uncertainties. Additionally, current development in material science and other areas requires the quantification of the elements at lower levels with good sensitivity. Owing to their robustness and flexibility, mass spectrometry techniques provide vast possibilities for the quantification, spatial and isotopic analysis, including the solutions for direct analysis of solids. The current review focuses on the application of major mass spectrometric techniques for the quantification of N, O, F, Cl, and Br in solid samples. The following techniques are mainly considered: thermal ionization mass spectrometry (TIMS), isotope-ratio MS (IRMS), secondary ion MS (SIMS), inductively coupled plasma MS (ICP-MS), and glow discharge MS (GDMS); as the most accessible and widely applied for the purpose. General ionization issues, advantages, limitations, and novel methodological solutions are discussed.

The aim of the study was to investigate the possibility of using а concentration of aluminum as a marker of neurodegenerative diseases.Material and methods. To achieve this goal, there was carried out an analysis of literary origins from various databases, in particular Scopus and PubMed.Results. The analysis shows that by now there has been accumulated strong evidence that certain neurodegenerative diseases are associated with chronic exposure to low-dose of aluminum: in particular, Alzheimer's disease (AD); motor neuron disease or amyotrophic lateral sclerosis (ALS); multiple sclerosis (MS) and a number of others.Conclusion. Thus, it can be assumed that the measurement of the concentration of Al in the blood plasma will make it possible to identify a group people with of high risk of AD, which will allow starting preventive treatment at the earliest stage of the disease. The capabilities of the existing methods of analysis: atomic absorption spectrometry with electrothermal atomization (GFAAS) and inductively coupled plasma mass spectrometry (ICP-MS) enable to solve this problem.

A recent trend in glow discharge analysis, previously considered as a 'purely inorganic' technique, is related to the effective ionisation of volatile organic compounds (VOCs). This approach was demonstrated to be capable of analysing VOCs in both model gas mixtures and ambient air. In the current study, the possibility of the direct determination of VOCs of different classes of organic compounds (including toluene, p-xylene, chlorobenzene and 1,2,4-trimethylbenzene) in ambient air using microsecond pulsed glow discharge time-of-flight mass spectrometry (mu s-Pulsed GD TOFMS) with copper hollow cathode was demonstrated. The ionisation processes with the formation of molecular ions M+, which can be used for quantification, were discussed. The fragmentation of detected molecular ions of VOCs was found to be quite low, which benefits both qualitative and quantitative determination. The ease of identification and relative simplicity of the mass spectrum is promising for the analysis of VOC mixtures. One of the possible applications of the designed method is the direct determination of VOCs in human exhaled breath for the diagnosis of lung diseases, including lung cancer. However, revealing its potential applicability for this purpose requires further research.

Direct analysis of matrix and admixture elements in non-conducting crystals is a relevant analytical task in terms of quality assurance of optical materials. The current study aimed to develop a method capable to assess the inhomogeneity of optical crystals with sufficient sensitivity. K1−xRbxTiOPO4 (x = 0.002 and 0.05) and KGd1−yNdy(WO4)2 (y = 0.05) were grown using the top-seeded solution growth method (TSSG). The samples were analyzed by microsecond direct current pulsed glow discharge time-of-flight mass spectrometry (µs-PDC TOF GDMS). The data were compared with the results obtained by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM EDX) and spectrophotometry and validated by the analysis of certified reference material. Sample glow discharge sputtering and analysis were optimized and implemented in real samples. Sample coating with a silver layer and sample pressing in the metallic matrix were proposed to ensure effective sputtering for K1−xRbxTiOPO4 and KGd1−yNdy(WO4)2, respectively. Using the designed method, the inhomogeneity of the dopant’s distribution was demonstrated along the growth axis and in the case of K1−xRbxTiOPO4, also in the growth sectors of different faces. The designed method is applicable for the direct analysis of optical crystal and may be implemented in quality assurance in the manufacturing of optical materials.

The pollution of the environment with uranium dictates the need to control the concentration of this element in natural waters to the permissible limits for the stability of the ecosystems and public health. In 2011, WHO set maximum permissible concentration of uranium in water to 0.03 ppm due to the strong toxicity and radioactivity of uranium in water. Therefore, the continuous monitoring of uranium content is an important task for the safety and health of the citizens. To determine the low uranium content in natural waters, the conservation of the studied solutions is necessary. However, this method of storage and transportation is not always simple. In the current paper, as a convenient method of concentrating uranium, preserving the sample and transporting it, we used the method of sorbing uranium on sorbents. Single-layer carbon nanotubes were used as sorbents. Their surfaces were modified using wet chemical oxidation and synthesis with Aerosil A-380 silica. Two schemes were considered for concentrating the uranium on the surface of the sorbent: individual carbon nanotubes and nanotubes modified with silica. The direct analysis was used to determine the content of uranium in the sorbent, namely, time-of-flight mass spectrometry with the pulsed glow discharge (GD-MS). The most effective approach for the determination of uranium in water was the sorption of uranium on the tablet consisting of oxidized nanotubes modified with silica. The limit of detection in this case was 0.2 ppb.

RationaleDopants in ionic conductors play a crucial role in achieving the required electrochemical properties. A slight variation in their concentration considerably affects the conductivity of crystals and their applicability as ionic conductors and laser materials. To ensure the growth of high‐quality fluoride crystals, adequate approaches for the quantification of matrix and admixture/dopant components are required.MethodsA panel of SrF2‐ and GdF3‐doped LaF3 single crystals was investigated. The electrical conductivity of the crystals was measured using impedance spectroscopy in the frequency range 100 Hz–1 MHz to control for crystal quality. Pulsed glow discharge mass spectrometry (GDMS) was used to simultaneously quantify fluorine, strontium, lanthanum, and gadolinium in the crystals. X‐ray fluorescence, scanning electron microscopy–energy dispersive X–ray spectroscopy, and arc optical emission spectrometry were used for validation.ResultsQuasiperiodic intensity drifts under sputtering of the ionic conductors were observed and attributed to F− redistribution on the sample surface, affecting surface conductivity and sputtering rate. Several sample preparation protocols were tested to address that effect. Full coating of the sample with a layer of silver several micrometers thick provided stable and effective sputtering. The parameters for the GDMS determination of F, Sr, La, and Gd were optimized. The elements' distribution was studied in different parts of the crystals.ConclusionsAn analytical approach to the direct multi‐element analysis of fluoride‐containing ionic conductors using pulsed GDMS with La1−x−ySrxGdyF3−x as an example was designed and tested. Instability effects of ionic conductivity were explained and coped with, providing effective and stable sputtering.

Recently glow discharge (GD) mass spectrometry, which is conventionally used to analyze solid samples, was successfully applied for ionization and the subsequent determination of volatile organic compounds (VOCs). In the present study, the possibility of direct determination of VOCs in ambient air using time-of-flight mass spectrometry with microsecond pulsed discharge in a copper hollow cathode was considered for the first time. The discharge cell of the mass spectrometer was modified for the direct analysis of gaseous samples by the introduction of a quartz capillary into the argon input channel. Various classes of compounds (aromatic and aliphatic hydrocarbons and derivatives of carboxylic acids) were studied. Particular attention was paid to the ionization mechanisms of VOCs. New mechanisms of chemical and electron ionization, resulting in the formation of associate ions with cathode material (copper) – CuM+, were demonstrated and implemented. Alternative mechanisms of organic compounds ionization in GD may be related to Penning process and proton transfer reactions. These processes are mainly responsible for the formation of molecular and protonated molecular ions. The relative contribution of all these mechanisms can be adjusted by operating parameters. In general, an extremely low degree of fragmentation of molecular ions or associates was observed. Due to its isotopic structure (only two isotopes 63Cu and 65Cu with comparable abundances), the use of copper as cathode material additionally increases the reliability of VOC identification in the form of their CuM+ associates. Such association shifts the detected ions to the region of large masses with fewer interferences and noise related to scattered ions.

A combined hollow cathode microsecond direct current pulsed glow discharge time-of-flight mass spectrometry system has proved its efficiency for quantification; however, it has not been properly tested for the purpose of depth analysis.

A methodological approach for the direct determination of mercury in the blood using analyzer RA-915 with pyrolytic decomposition of the sample has been developed. The detection limit of the proposed technique is 0,5 µg/L with the relative standard deviation not exceeding 10%. To determine the lead content, the previously created method of direct lead determination in the blood has been used. In the second stage of the study, biomonitoring of pregnant women has been carried out in order to identify the relationship between the termination of pregnancy in early terms with the content of mercury and lead in women’s blood. The study involved 25 women with a diagnosis of non-developing pregnancy, and 47 women from the control group. As a result of the conducted studies, it has been found that the contents of mercury and lead in women with nondeveloping pregnancy were almost 25% higher.

We optimized procedures for the collection, preparation, and storage of samples of exhaled air and the conditions for determining volatile organic compounds in exhaled air by gas chromatography–mass spectrometry (GC–MS), the presence or change in the concentration of which can be caused by lung cancer. The analysis circuit includes group adsorption preconcentration followed by the thermal desorption and determination of analytes by GC–MS. Polymer bags of a Tedlar® film were used for sample collection. The conditions and periods of the storage of samples in bags and adsorption tubes are determined. A method for cleaning and conditioning bags is proposed. For preconcentrating exhaled air components, we used hydrophobic adsorbents (Porapak™ P, Porapak™ Q, and Tenax® TA) and three-section tubes containing Tenax® GR, Carbopack™ B, and Carbosieve® S-III. Their relative efficiency was evaluated by assessing the residual background of gas emission from the adsorbent, the magnitude of the analytical signal, the efficiency of adsorption/desorption, and the efficiency of storage. The conditions for the preconcentration of volatile organic compounds (volume and rate of aspiration, time, and temperature of thermal desorption) are optimized. The main volatile organic compounds in the exhaled air of conditionally healthy volunteers were identified, and their concentrations are evaluated.