Boosting the sensitivity of single photon ionization time-of-flight mass spectrometry using a segmented focus quadrupole-ion guide.

Single photon ionization time-of-flight mass spectrometry (SPI-TOF-MS) is a powerful analytical technique for real-time detection of trace VOCs. However, efficient ion transmission within the ionization chamber has always been a challenging issue in SPI-TOF-MS. In this study, a novel ion guide termed the Segmented Focus Quadrupole Ion Guide (SFQ-IG) was introduced for SPI-TOF-MS. The SFQ-IG device consists of 12 printed circuit boards (PCB), each containing four quarter-ring electrodes with inner diameters progressively decreasing from 26 to 4 mm. The simulation results demonstrated that SFQ-IG exhibited superior ion transmission efficiency than both ion funnel (IF) field and direct current-only (DC-only) field. By integrating into a SPI-TOF-MS, this ion guide was optimized in terms of the ionization source pressure, direct current gradient, and radio frequency amplitude. Further comparative experiments demonstrated that the SPI-TOF-MS with the SFQ-IG exhibited higher sensitivity than both the IF field (1.3-7.4 times) and DC-only field (3.5-8.8 times) for the test VOCs. The improvements in limit of detection (LOD) with the SFQ-IG ranged from 1.6 to 5.3 times compared to the DC-only field for the test VOCs. Fabricated using PCB technology, the SFQ-IG is characterized by its cost-effectiveness, compact size, and high transmission efficiency, facilitating its integration into other mass spectrometers.

Simultaneous and on-line detection of organic and heavy metal components in water using a novel nebulization-assisted injection plasma ionization triple quadruple mass spectrometry instrument.

BACKGROUND: The global release of organic and heavy metal components into natural water bodies is a major concern for the environment and human health. The assessment of water quality relies on analyzing organic and heavy metal components qualitatively and quantitatively. Real-time identification of organic and metal components in water systems requires different analytical techniques due to varying measurement requirements. Thus, on-line detecting both organic compounds and heavy metals in ambient water systems simultaneously using a single instrumentation setup presents a significant challenge. RESULTS: In this study, an analytical technique of nebulization-assisted injection plasma ionization mass spectrometry (NI-PIMS) was developed. This novel method enables the simultaneous detection of heavy metals and organic compounds in water system with high sensitivity, which has been demonstrated by the limit of quantification (LOQ) values below 1.0 µg/L for the three sterols (Enrofloxacin, ciprofloxacin, and clenbuterol) and three heavy metals (Pb, Ba, and Cd). Moreover, the method was successfully applied to rapidly analyze real water samples from urban and rural areas in China. The analytical results are available in less than 0.5 min, and only a few microliters of sample are required for each analysis. SIGNIFICANCE AND NOVELTY: As far as we know, this is the first report of on-line simultaneous analysis of organic compounds and heavy metals in a water system using a single mass spectrometry instrument. Compared to traditional methods, NI-PIMS demonstrates higher efficiency, sensitivity, no or lower sample preparation, and less sample consumption. The advancement and widespread use of this technology are expected to enhance the effectiveness of mass spectrometers, broaden the applications, and play an important role in complex sample analysis in fields such as atmospheric science, environmental science, and earth science.

Nonderivatized Method for the Detection of Perfluoroalkane Sulfonyl Fluorides by Liquid Chromatography-Microwave Plasma Torch Ionization Mass Spectrometry.

Per- and polyfluoroalkyl substances (PFAS) have caused widespread environmental concern in recent years. Among them, the levels of perfluoroalkane sulfonyl fluorides (PFASFs) in the environment have rarely been reported due to the lack of sensitive analytical methods. Herein, a novel liquid chromatography-microwave plasma torch ionization-mass spectrometry (LC-MPTI-MS) technique was designed for the direct analysis of PFASFs in the environment. The collaborative action of reactive oxygen species (such as hydroxyl radicals) and the elevated temperature within the ambient MPTI environment results in the replacement of the fluorine atom in sulfonyl fluoride by oxygen, leading to the detection of perfluoroalkanesulfonic acid (PFSA) ions by MS. Concurrently, LC was employed to separate other PFSAs that are present in the environment. Three PFASFs exhibited good linearity within the range of 1-500 µg/L with R2 > 0.994. The limit of detections (LODs) and the limit of quantifications (LOQs) were measured at 39.32-87.87 and 131.07-292.90 ng/L, respectively. The method was utilized for the direct detection of spiked perfluorooctane sulfonyl fluoride (PFOSF) in wastewater with recoveries of 77.16 to 124.81%. Our approach circumvents the laborious process of chemical derivatization and is anticipated to serve as a robust tool for determining the levels and behaviors of PFASFs in the environment.

Analysis and identification of degradation products in gas, particle, and liquid phases of polypropylene and polyethyleneterephthalate microplastics aging through non-thermal plasma simulation.

Plastic aging can cause alterations in the physical and chemical characteristics of plastics, as well as their behavior in the environment. Due to the extremely slow natural aging process, laboratory simulated aging methods have to be used. In this study, non-thermal plasma (NTP) was adopted to investigate the aging process of polypropylene (PP) and polyethylene terephthalate (PET) microplastics. Various analytical instruments, including proton transfer reaction mass spectrometry and single-particle aerosol mass spectrometry, were employed to examine and identify the organic constituents of the gas, liquid, and particle phase degradation products, as well as to monitor the degradation process. The results showed that after 90 min of aging, both PP and PET surfaces showed yellowing, and the carbonyl index of PP increased while that of PET decreased, with an increase in crystallinity. The organic components of reaction products, such as ketones, esters, acids, and alcohols, increased with longer aging times. Gas products mainly contain aromatic hydrocarbons, while particles from aged PET contain compounds with benzene rings and metal elements. Liquid products from aged PP show a significant presence of branched alkanes. Based on this analysis, degradation mechanisms of PP and PET by NTP were proposed. This investigation represents the initial systematically exploration of the release of organic substances during the degradation of microplastics mediated by NTP. It provides significant insights into the detrimental organic compounds emitted during this process, thereby offering valuable information for understanding the environmental and human health implications of natural microplastic degradation. Furthermore, it addressed the requirements for increased attention to the potential environmental risks associated with these harmful components.

Development of Low-Pressure He-MC-MIP-MS and Its Application for Oxygen Isotopic Analysis.

In Ar-based inductively coupled plasma mass spectrometry (MS), Ar-related interference and the low ionization capacity of the Ar-ion source prevent facile and precise determination of certain elements. To address this problem, we investigated the application of microwave-induced plasma (MIP), and we improved its ionization capacity using He as the working gas. The MIP ion source was connected to a multicollector mass spectrometry (MC-MS) apparatus to improve the accuracy and precision of the isotopic analysis. A vacuum pump was used to achieve a low pressure (200-300 Pa) at the interface. The analytical figures of merit were discussed and evaluated by measuring the oxygen isotopes in oxygen. With the application of low-pressure He-MC-MIP-MS, the degree of ionization of oxygen could be significantly improved with He plasma. The interference of oxygen from the atmosphere could also be eliminated with low-pressure plasma, and the determination precision of oxygen isotopes could be improved with the application of MC-MS. Subsequently, using this method, 16O18O/16O16O was applied as the analytical ratio to investigate the interference, sensitivity, and precision. With this constructed method, the obtained long-term producibility of δ18O was 0.16‰ (2 SD), and the measured result for oxygen was consistent with that obtained by MAT 253 within the uncertainty limit. The development of low-pressure He-MC-MIP-MS can pave the way for the accurate measurement of nonmetal isotopes and easily interfered isotopes in Ar plasma.

Rapid analysis of pharmaceutical and personal care products by soft microwave-based plasma ionization-linear ion trap mass spectrometer (SMPI-LTQ) in natural water.

In this study, a soft microwave plasma torch (SMPT) combined with a mass spectrometer (MS) was used for the first time as an analytical method to detect and analyze various pharmaceutical and personal care products (PPCPs) in aquatic environments without the need for sample pretreatment. For this purpose, ambient SMPT was used to generate plasma for ionizing the analyte molecules. Accordingly, nine PPCPs were identified by the SMPT-MS, and their identification was verified by collision-induced dissociation (CID). The technique's performance was verified with known PPCP samples, and the limits of detection (LOD) and quantification (LOQ) obtained over a linear range of 50-1 µg/L were 1.56 to 2.81 and 2.07 to 3.62 µg/L, respectively, with the standard addition recovery rate falling between 87.14 and 115.16%. These results show that the method has excellent sensitivity and selectivity, suggesting that SMPT can rapidly and directly detect PPCPs in environmental water, making it a promising method for rapid water quality inspection.

Online study of the plasma-accelerated aging process and toxicity of polyethylene terephthalate.

Plastic aging occurs in all environmental media and affects their environmental behavior and toxicity. In this study, non-thermal plasma was applied to simulate the aging process of plastics, with polyethylene terephthalate (PET-film) being used as a model. The surface morphology, mass defects, toxicity of aged PET-film and the generation of airborne fine particles were comprehensively characterized. The surface of PET films began to become rough and then gradually became uneven, generating pores, protrusions and cracks. The toxicity of aged PET films was assessed in Caenorhabditis elegans which significantly reduced head thrashing, body bending and brood size. A single particle aerosol mass spectrometry instrument was used to characterize the size distribution and chemical composition of airborne fine particles in real-time. Few particles were observed during the first 90 min, while the generation of particles accelerated significantly after aging time beyond 90 min. For two pieces of PET film with surface area of 5 cm2, during the 180 min, at least 15113 ± 153 fine particles were generated, having a unimodal size distribution with a peak of 0.4 µm. The main components of these particles included metals, inorganic non-metals, and organic components. The results provide useful information on plastic aging and are beneficial in assessing the potential environmental risks.

Three-dimensional spatiotemporal variability of CO2 in suburban and urban areas of Shaoxing City in the Yangtze River Delta, China.

Metropolitan areas are the most anthropogenically active places but there is a lack of knowledge in carbon dioxide (CO2) spatial distribution in suburban and urban areas. In this study, the CO2 three-dimensional distributions were obtained from 92 times vertical unmanned aerial vehicle (UAV) flight observations in Shaoxing suburbs and 90 times ground mobile observations in Shaoxing urban areas from Nov. 2021 to Nov. 2022. The vertical distribution showed that CO2 concentrations gradually decreased from 450 to 420 ppm with altitude from 0 to 500 m. CO2 vertical profile concentrations can be influenced by transport from multiple regions. Based on the vertical observation data combining a potential source contribution function (PSCF) model, Shaoxing suburban CO2 were to be derived from urban areas in spring and autumn, while in winter and autumn were mainly from the long-transports from neighboring cities. Further the CO2 concentrations of urban horizontal distribution were observed in the range of 460-510 ppm through the mobile campaigns. Urban CO2 were partly emitted from traffic exhausts and residential combustion. Overall, CO2 concentrations were observed to be lower in spring and summer due to the CO2 uptake by plant photosynthesis. This uptake was initially quantified and accounted for 4.2 % of total CO2 in suburbs and 3.3 % in urban areas by calculating the decrease in CO2 concentration from peak to trough in the daytime. Compared with the CO2 observed in the Lin'an background station, the maximum regional CO2 enhancement in Shaoxing urban areas reached to 8.9 % while the maximum in suburbs only 4.4 %. The contribution differences between urban and suburban areas to regional CO2 were relatively constant at 1.6 % in four seasons may be mainly ascribed to the contribution of long-range CO2 transport to the suburbs.

Catalyst-Free Oxidation Reactions in a Microwave Plasma Torch-Based Ion/Molecular Reactor: An Approach for Predicting the Atmospheric Oxidation of Pollutants.

The atmospheric oxidation of chemicals has produced many new unpredicted pollutants. A microwave plasma torch-based ion/molecular reactor (MPTIR) interfacing an online mass spectrometer has been developed for creating and monitoring rapid oxidation reactions. Oxygen in the air is activated by the plasma into highly reactive oxygen radicals, thereby achieving oxidation of thioethers, alcohols, and various environmental pollutants on a millisecond scale without the addition of external oxidants or catalysts (6 orders of magnitude faster than bulk). The direct and real-time oxidation products of polycyclic aromatic hydrocarbons and p-phenylenediamines from the MPTIR match those of the long-term multistep environmental oxidative process. Meanwhile, two unreported environmental compounds were identified with an MPTIR and measured in the actual water samples, which demonstrates the considerable significance of the proposed device for both predicting the environmental pollutants (non-target screening) and studying the mechanism of atmospheric oxidative processes.

A Novel Integrated APCI and MPT Ionization Technique as Online Sensor for Trace Pesticides Detection.

The misuse of pesticides poses a tremendous threat to human health. Excessive pesticide residues have been shown to cause many diseases. Many sensor detection methods have been developed, but most of them suffer from problems such as slow detection speed or narrow detection range. So, the development of rapid, direct and sensitive means of detecting trace amounts of pesticide residues is always necessary. A novel online sensor technique was developed for direct analysis of pesticides in complex matrices with no sample pretreatment. The portable sensor ion source consists of an MPT (microwave plasma torch) with desolventizing capability and an APCI (atmosphere pressure chemical ionization), which provides abundant precursor ions and a strong electric field. The performance which improves the ionization efficiency and suppresses the background signal was verified by using pesticide standard solution and pesticide pear juice solution measurements with an Orbitrap mass spectrometer. The limit of detection (LOD) and the limit of quantization (LOQ) of the method were measured by pear juice solutions that were obtained in the ranges of 0.034-0.79 µg/L and 0.14-1 µg/L. Quantitative curves were obtained ranging from 0.5 to 100 µg/L that showed excellent semi-quantitative ability with correlation coefficients of 0.985-0.997. The recoveries (%) of atrazine, imidacloprid, dimethoate, profenofos, chlorpyrifos, and dichlorvos were 96.6%, 112.7%, 88.1%, 85.5%, 89.2%, and 101.9% with the RSDs ranging from 5.89-14.87%, respectively. The results show that the method has excellent sensitivity and quantification capability for rapid and direct detection of trace pesticide.

Dual ambient plasma source ionization mass spectrometry for the rapid detection of trace sterols in urban water: Rapid detection of trace sterols in urban water.

A direct analytical method based on dual ambient plasma ion source tandem mass spectrometry was used for the simultaneous determination of four sterols in the environment. This technology has very high sensitivity and the method detects the four sterols in methanol-water (1:3) solutions with limits of detection (LOD) and limits of quantification (LOQ) ranging from 1.2 ng/L to 6.9 ng/L and 7.6 ng/L to 10.0 ng/L, respectively. The method was also used to test water quality at three locations within the city and successfully detected all four sterols at very low concentrations. The dual plasma source tandem mass spectrometry technique is extremely simple, rapid, sensitive and highly efficient compared to other traditional methods, providing a useful screening tool for sterols in water.

Rapid Analysis of Trace Phthalates by Spray-Inlet Microwave Plasma Torch Ionization Tandem Mass Spectrometry in Commercial Perfumes.

BACKGROUND: The less volatile fraction of perfumes is susceptible to contamination by phthalate esters (PAEs), which are endocrine-disrupting chemicals encountered during the production, bottling, and transportation processes. There is a need to establish an innovative and rapid method for the determination of trace PAEs in commercial perfumes. OBJECTIVE: Therefore, self-built spray-inlet microwave plasma torch (MPT) ionization coupled with quadrupole time-of-flight (QTOF) tandem MS (MS/MS) was developed for the direct analysis of PAEs in perfumes without sample pretreatment. METHODS: Perfumes were sprayed directly onto the flame of the MPT by means of a sampling pump at a rate of 10 µL/min and the ions produced by the MPT were introduced into the QTOF-MS equipment with the MPT operating at 2450 MHz and 40 W at a flow rate of 800 ml/min of argon. RESULTS: For the established method, excellent linearity was obtained with a correlation coefficient of 0.9799 for di-n-pentyl phthalate and of greater than 0.99 for the other substances tested. The LOD and LOQ obtained were in the ranges of 1.452-18.96 and 4.839-63.19 ng/g, respectively. The spiked recoveries of PAEs ranged from 100.1 to 105.2% with satisfactory intraday RSDs and interday RSDs ranging from 1.51 to 4.34% and 3.45 to 5.65%, respectively. PAEs in commercial perfumes were successfully detected by spray-inlet MPT-MS/MS with low concentrations ranging from 0.036 to 1.352 µg/g. CONCLUSIONS: The method is a promising tool for the on-site analysis of PAEs in cosmetic solutions requiring rapid qualitative and quantitative analysis. HIGHLIGHTS: The method was successfully applied to the analysis of the commercial perfume samples within 30 s, and displayed the merits of simplicity, sensitivity, environmental friendliness and ease of operation.

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.

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.