Ambient Mass Research Articles

Rapid desorption and analysis for illicit drugs and chemical profiling of fingerprints by SICRIT ion source.

Forensic analysis can encompass a wide variety of analytes from biological samples including DNA, blood, serum, and fingerprints to synthetic samples like drugs and explosives. In order to analyze this variety, there are various sample preparation techniques, which can be time-consuming and require multiple analytical instruments. With recent advancements in ambient ionization mass spectrometry (MS), plasma-based dielectric barrier discharge ionization (DBDI) sources have demonstrated to cover a wide range of these analytes. The flow-through design of this source also allows for easy connection to a thermal desorption type of sample introduction. We present an in-house built thermal desorption device where the sample is introduced via a glass slide, which gets heated and transferred to the DBDI-MS with nitrogen for identification and semi-quantification. Using a glass slide as an inexpensive sampling device, detection limits as low as 20 pg for fentanyl are demonstrated. Additionally, a very precise (>96% accuracy) identification of persons based on the chemical profile of their fingerprints is possible, establishing a direct analytical link of the drug trace to the individual in one measurement. We compared the DAG, TAG, sterol, and (semi-)volatile region of the averaged fingerprint spectra over multiple days, showing the best model accuracy for identification based on the DAG region. The combination of thermal desorption and DBDI-MS minimized sample preparation, leading to an ultrasensitive and rapid analysis of illicit drug traces and the identification of underlying personas based on fingerprints.

Designing a Novel Setup for High-Throughput Investigations of Electrochemical Reactions in Real Time

With the great interest in new electrochemical processes, fast screening of various reaction parameters is highly desirable. For this purpose, differential electrochemical mass spectrometry (DEMS) and membrane-inlet mass spectrometry (MIMS) have been established to enable real-time monitoring of volatile compounds. However, the analysis of non-volatile compounds is commonly limited by the temporal resolution of traditional quantification methods such as NMR, GC-MS, or LC-MS. While ambient ionization mass spectrometry (AIMS) generally enables time-resolved monitoring of non-volatile compounds, electrolyte salts can lead to ionization suppression. The latter can decrease the sensitivity of product detection and the reliability of quantitative data. Therefore, a suitable reaction setup and thorough investigations are needed when utilizing AIMS. Nonetheless, in recent efforts, an electrochemical flow cell was coupled with such a technique to provide a method for on-line monitoring of non-voltile reaction products in aqueous electrolytes. To keep up with the increasing interest in electrosynthesis in organic media, we now present a new setup that is also applicable to non-aqueous media. It pairs a novel and versatile electrochemical cell with an AIMS and DEMS for highly sensitive detection of reaction products. Moreover, various reaction parameters such as electrode material, electrolyte, and temperature can be investigated in high-throughput.Key words: Electrocatalysis, Electrosynthesis, Real-time, On-line monitoring, High-throughput

Photocatalytic degradation-based ambient mass spectrometry imaging for enhancing detection coverage of poorly-ionizable lipidomes

Localization of lipidomes and tracking their spatial changes in tissues by mass spectrometry imaging (MSI) plays an important role in unveiling the mechanisms of living processes, diseases and therapeutic treatments. However, it is always challenging to achieve direct MSI of poorly-ionizable lipids, such as glycolipids and glycerolipids, due to the strong ion suppression and isobaric peaks interference from high-abundance phosphatidylcholines (PCs) in tissues. Here we developed a photocatalytic degradation-based ambient liquid extraction MSI method to largely enhance the detection coverage of poorly-ionizable lipids by rapid online removal of PCs in MSI. Phospholipids were found to be selectively photodegraded on TiO2 surface in acidic conditions in the presence of water under UV irradiation, while other poorly-ionizable lipids remained. Sulfate ion could largely improve the degradation efficiencies. Anatase nanoparticles-embedded TiO2 monolith was in-situ synthesized in the capillary of ambient liquid extraction system, and rapid online photodegradation of PCs was achieved during MSI with efficiency >80 %, largely reducing ion suppression. The pathway analysis showed that PC was oxidatively degraded starting from hydroxylation of C=C bonds. With intense UV irradiation, PCs were completely degraded into small molecules<200 Da without interference on the detection of endogenous lipids. With the new MSI method, detection coverage to cerebrosides, ceramides and diglycerides was enhanced by 2–9 times comparing with traditional MSI. Clearer localizations were observed for poorly-ionizable lipids via the new method than traditional method. Thus, this work provided a complementary MSI method for traditional MSI to address the issues on direct imaging of poorly ionizable lipids in ambient conditions.

An adaptive cabin air recirculation strategy for an electric truck using a coupled CFD-thermoregulation approach

Cabin climatization is one of the largest auxiliary loads in an electric vehicle, and its performance significantly affects the driving range. Recirculating climatized air from the cabin has been shown to reduce energy consumption, but at the risk of fogging the windows and deteriorating the air quality. Therefore, many automobile manufacturers refrain from adopting it at low ambient temperatures. In this paper, an adaptive recirculation strategy that takes these issues into account is proposed and studied on an electric truck cabin while heating. Numerical simulations were performed using a coupled CFD-thermoregulation model, with the consideration of humidity and CO2. The JOS-3 thermoregulation model was employed for estimations of skin temperatures and evaporation of vapor from the skin, and the Berkeley comfort model was used to evaluate the comfort metrics. Ten scenarios were considered at various vehicle speeds, temperatures, and relative humidity levels while evaluating them with and without the proposed return-air strategy. The controller adapted between humidity and CO2-critical conditions during run-time. The fresh-air mass flow requirements reduced with increasing difference between the setpoint and ambient vapor mass fractions under humidity critical conditions, and plateaued at 10 g/s where CO2 was more critical. The proposed strategy provided energy savings ranging from 9% to 34% depending on the operating condition.

Determination of MCPA in environmental samples using an analytical on-line system based on imprinted poly[2-(3-butenyl)-2-oxazoline] and ambient ionization mass spectrometry

Monitoring and quantifying organic chemicals in the environment play a vital role in understanding their behavior and ensuring environmental safety. MCPA (2-methyl-4-chlorophenoxyacetic acid) is a commonly used phenoxy herbicide that poses potential risks to aquatic life. In this study, we present an innovative analytical approach for MCPA quantification, employing molecularly imprinted polymers (MIPs) for selective extraction and ambient plasma mass spectrometry for direct on-line analysis. To synthesize functional MIPs, we employed a post-polymerization strategy based on a thiol-ene click reaction conducted on a short-chain poly[2-(3-butenyl)-2-oxazoline] (poly(ButenOx)) that allowed attachment of 3-mercaptopropionic acid (MPA) to polymer side chains. The incorporation of MPA groups into polymer structure enabled the attainment of elevated maximum adsorption capacities and enhanced selectivity towards MCPA. Utilizing a specially designed ambient plasma mass spectrometry setup, we successfully quantified MCPA in water samples, achieving significantly improved detection limits compared to conventional solution-based analysis, whereas the quantification of MCPA in real-life river water samples demonstrated excellent recoveries. In conclusion, this novel analytical method employing MIPs and ambient plasma mass spectrometry provides an effective and sensitive approach for accurate MCPA detection in environmental water samples. The technique holds promise for facilitating reliable monitoring and management of MCPA levels in aquatic ecosystems.

Selectivity of Explosives Analysis with Ambient Ionization Single Quadrupole Mass Spectrometry: Implications for Trace Detection.

Ambient ionization (AI) is a rapidly growing field in mass spectrometry (MS). It allows for the direct analysis of samples without any sample preparation, making it a promising technique for the detection of explosives. Previous studies have shown that AI can be used to detect a variety of explosives, but the exact gas-phase reactions that occur during ionization are not fully understood. This is further complicated by differences in mass spectrometers and individual experimental set ups between researchers. This study investigated the gas-phase ion reactions of five different explosives using a variety of AI techniques coupled to a Waters QDa mass spectrometer to identify selective ions for explosive detection and identification based on the applied ambient ionization technique. The results showed that the choice of the ion source can have a significant impact on the number of ions observed. This can affect the sensitivity and selectivity of the data produced. The findings of this study provide new insights into the gas-phase ion reactions of explosives and could lead to the development of more sensitive and selective AI-based methods for their detection.

Evaluation of nasal delivery systems of olanzapine by desorption electrospray ionization mass spectrometry imaging

Nose-to-brain delivery presents an attractive administration route for neuroactive drugs that suffer from compromised bioavailability or fail to pass the blood–brain barrier. However, the conventional gauge of effectiveness for intranasal delivery platforms primarily involves detecting the presence of the administered drug within the brain, with little insight into its precise localization within brain structures. This may undermine the therapeutic efficacy of drugs and hinder the design of systems that target specific brain regions. In this study, we designed two intranasal delivery systems for the antipsychotic drug, olanzapine, and evaluated its distribution in the rat brain following intranasal administration. The first evaluated system was an olanzapine-loaded microemulsion and the second one was nanoparticulate aqueous dispersion of olanzapine. Both systems exhibited characteristics that render them compatible for intranasal administration, and successfully delivered olanzapine to the brain. We further employed an ambient mass spectrometry imaging method, called desorption electrospray ionization mass spectrometry imaging, to visualize the signal intensity of olanzapine in different brain regions following the intranasal administration of these two systems. Substantial variations in the distribution patterns of olanzapine across various brain structures were revealed, potentially highlighting the importance of mass spectrometry imaging in designing and evaluating intranasal drug delivery platforms.

Pulled Flowprobe for Ambient Liquid Extraction-Based High Spatial Resolution Mass Spectrometry Imaging with Enhanced Sensitivity and Stability.

Ambient liquid extraction techniques enable direct mass spectrometry imaging (MSI) under ambient conditions with minimal sample preparation. However, currently an integrated probe for ambient liquid extraction-based MSI with high spatial resolution, high sensitivity, and stability is still lacking. In this work, we developed a new integrated probe made of pulled coaxial capillaries, named pulled flowprobe, and compared it with the previously reported single-probe. Mass transfer kinetics in probes was first investigated. The extraction kinetic curves during probe sampling indicate a narrower and higher peak shape for the pulled flowprobe than single-probe. Computational fluid dynamics analysis reveals that in the pulled flowprobe flow velocities are lower in liquid microjunction and higher in the transferring channels, resulting in higher extraction efficiencies and reduced band diffusion compared with single-probe and other probes with a similar flow route. Results of ambient liquid extraction-based MSI of lipids in rat cerebrum show that signals of low-abundance lipids were 2-5 times higher via a pulled flowprobe than via a single-probe, and 26 more lipid species were detected on brain tissue via a pulled flowprobe than via a single-probe. The stability of MSI with the pulled flowprobe was found to be higher than that with single-probe (averaged relative standard deviation = 18% vs 80%) by imaging a lab-made uniform ink coating. Moreover, in the pulled flowprobe, no retraction of the inner capillary from outer capillary is optimal for both sensitivity and stability. The spatial resolution of the pulled flowprobe (30-40 μm) was measured to be higher than that of a comparable size single-probe by calculation with the "80-20" rule. Finally, the new pulled flowprobe was applied to high-resolution MSI of lipids in the hippocampus, and localization of several lipids to the specific cell layers in the hippocampus region was observed. Thus, this work provides an alternative easily fabricated sampling probe with enhanced sensitivity, stability, and spatial resolution, promoting the use of ambient liquid extraction-based MSI in biological and clinical research.

Triboelectric nanogenerator-coated blade spray mass spectrometry for volume-limited drug analysis

The demand for analytical tools for the analysis of low-concentration volume-limited samples has driven researchers to explore new analytical approaches. Mass spectrometry excels at trace analysis due to its high sensitivity and specificity, whereas ambient methods simplify, or completely eliminate sample preparation. Herein, we report a triboelectric nanogenerator-coated blade spray ambient mass spectrometry (TENG-CBS MS) method for the extraction, elution, and ionization of volume-limited, low-concentration small molecule drug samples with minimum sample preparation. Using a TENG device as the CBS power supply, we show it is possible to extract and analyze drug samples in a pulsed fashion at sub-nanogram to picogram levels with good stability and reproducibility. A wide range of analytes polarities were tested. Results indicated this method could also be useful for the analysis of low-level analytes in precious, volume limited samples in a simple single step.

Quantitative Determination of Water in Organic Liquids by Ambient Mass Spectrometry

AbstractThis study uses a rapid tandem mass‐spectrometry method to determine water content in complex organic solutions. Emphasis is placed on trace‐water analysis by a fast and accurate alternative to the Karl–Fischer method. In this new method, water is captured by a charge‐labeled molecular probe. Water binds strongly with high specificity to the strongly electrophilic aldehyde site in a charge‐labelled molecule (N‐methylpyridinium); competitive binding by other analytes is effectively discriminated against in the mass‐measurement step. Quantitative determinations are made over a wide concentration range, 0.001 % (10 ppm) to 99 %, with better than 10 % relative standard deviation, along with short (1 min) analysis times using small sample volumes (several μL). Applications include water measurement in simple organic solvents, for example, deuterated solvents, as well as in complex mixtures, for example, organic reaction mixtures. Additionally, this method allows for water monitoring in levitated droplets. Mechanistic investigations into the impact of water on important chemical processes in organic synthesis and environmental science are reported.

Quantitative Determination of Water in Organic Liquids by Ambient Mass Spectrometry.

This study uses a rapid tandem mass-spectrometry method to determine water content in complex organic solutions. Emphasis is placed on trace-water analysis by a fast and accurate alternative to the Karl-Fischer method. In this new method, water is captured by a charge-labeled molecular probe. Water binds strongly with high specificity to the strongly electrophilic aldehyde site in a charge-labelled molecule (N-methylpyridinium); competitive binding by other analytes is effectively discriminated against in the mass-measurement step. Quantitative determinations are made over a wide concentration range, 0.001 % (10 ppm) to 99 %, with better than 10 % relative standard deviation, along with short (1 min) analysis times using small sample volumes (several μL). Applications include water measurement in simple organic solvents, for example, deuterated solvents, as well as in complex mixtures, for example, organic reaction mixtures. Additionally, this method allows for water monitoring in levitated droplets. Mechanistic investigations into the impact of water on important chemical processes in organic synthesis and environmental science are reported.

Dual-use ionization source for direct and sensitive detection of trace carbamates residue

Directly determining trace compounds in actual sample by ambient ionization mass spectrometry (AIMS) has always been a challenge. Due to the excellent adsorption and desorption properties of nanomaterials, AIMS combined with nanomaterials can improve the adsorption and desorption properties of MS. In this work, we developed a molecularly imprinted graphene oxide coated steel sheet (MIGOCS) to be used as a solid phase extraction adsorbent. Graphene oxide was characterized by its strong adsorption abilities, and the surface molecularly imprinted polymer has high selectivity. Here, the MIGOCS coupled with the ambient electrospray ion source was used to detect trace carbamate pesticides in water samples. Meanwhile, the extraction and spray parameters were systematically optimized. The newly developed molecularly imprinted graphene oxide-steel sheet spray-mass spectrometry (MIGO-SS-MS) method has low detection limits (0.05 ∼ 0.4 ng mL−1) and satisfactory recoveries (83.23 ∼ 97.98 %) for carbamates (CMs). The method can be potentially applied to the determination of CMs in water and food samples.

Recent Advances and Applications of Ambient Mass Spectrometry Imaging in Cancer Research: An Overview.

Cancer metabolic variability has a significant impact on both diagnosis and treatment outcomes. The discovery of novel biological indicators and metabolic dysregulation, can significantly rely on comprehension of the modified metabolism in cancer, is a research focus. Tissue histology is a critical feature in the diagnostic testing of many ailments, such as cancer. To assess the surgical margin of the tumour on patients, frozen section histology is a tedious, laborious, and typically arbitrary method. Concurrent monitoring of ion images in tissues facilitated by the latest advancements in mass spectrometry imaging (MSI) is far more efficient than optical tissue image analysis utilized in conventional histopathology examination. This article focuses on the "desorption electrospray ionization (DESI)-MSI" technique's most recent advancements and uses in cancer research. DESI-MSI can provide wealthy information based on the variances in metabolites and lipids in normal and cancerous tissues by acquiring ion images of the lipid and metabolite variances on biopsy samples. As opposed to a systematic review, this article offers a synopsis of the most widely employed cutting-edge DESI-MSI techniques in cancer research.

Analysis of Pesticide Residues on Fruit Using Swab Spray Ionization Mass Spectrometry.

The vast quantity and high variety of pesticides globally used in agriculture entails considerable risks for the environment and requires ensuring the safety of food products. Therefore, powerful analytical tools are needed to acquire qualitative and quantitative data for monitoring pesticide residues. The development of ambient ionization mass spectrometry methods in the past two decades has demonstrated numerous ways to generate ions under atmospheric conditions and simultaneously to reduce the need for extended sample preparation and circumvent chromatographic separation prior to mass analysis. Swab spray ionization enables the generation of ions directly from swabs via the application of high voltage and solvent flow. In this study, swab sampling of fruit surfaces and subsequent ionization directly from the swab in a modified electrospray ion source was employed for the screening and quantitation of pesticide residues. Aspects regarding sample collection, sampling efficacy on different surfaces, and swab background are discussed. The effect of solvent composition on pesticide-sodium adduct formation and the suppression of ionization by the background matrix have been investigated. Furthermore, a novel approach for the quantitation of pesticide residues based on depletion curve areas is presented. It is demonstrated that swab spray ionization is an effective and quick method for spectral library-based identification and the quantitative analysis of polar contact pesticide residues on food.

Peroxides on the Surface of Organic Aerosol Particles Using Matrix-Assisted Ionization in Vacuum (MAIV) Mass Spectrometry.

Organic peroxides are key intermediates in the atmosphere but are challenging to detect, especially in the particle phase, due to their instability, which has led to substantial gaps in the understanding of their environmental effects. We demonstrate that matrix-assisted ionization in vacuum (MAIV) mass spectrometry (MS), which does not require an ionization source, enables in situ characterization of peroxides and other products in the surface layers of organic particles. Hydroxyl radical oxidation of glutaric acid particles yields hydroperoxides and organic peroxides, which were detected with signals of the same order of magnitude as the major, more stable products. Product identification is supported by MS/MS analysis, peroxide standards, and offline high-resolution MS. The peroxide signals relative to the stable carbonyl and alcohol products are significantly larger using MAIV compared to those in the offline bulk analysis. This is also the case for analysis using fast, online easy ambient sonic-spray ionization mass spectrometry. These studies demonstrate the advantage of MAIV for the real-time characterization of labile peroxides in the surface layers of solid particles. The presence of peroxides on the surface may be important for surface oxidation processes as well as for the toxicity of inhaled particles.

Systematic laboratory investigations concerning the reduction of uncertainties related to the modeling of the material behavior of crushed salt

Abstract. The planned use of crushed salt as the backfill and sealing material in the context of the final disposal of radioactive waste in rock salt is justified and favored by the realization that the material properties of loosely deposited crushed salt will be transformed into the material properties of in situ rock salt in the long term by the convergence of the viscous rock salt mass. In other words, the convergence-induced compaction of crushed salt ultimately results in a nearly pore-free material, with a tightness and creep capacity corresponding to that of the ambient rock salt mass. The computational prognosis of the load-bearing and sealing behavior required for the long-term safety assessment of underground repositories requires a sufficiently proven physical modeling of the, in general, three-dimensional load bearing and permeability behavior of crushed salt. This requirement can only be met if the influencing variables on the load bearing and permeability behavior are sufficiently quantified and represented by mathematical–physical functions on the basis of suitable laboratory and field investigations. In order to eliminate or reduce the currently (still) existing scientific deficits and uncertainties concerning the general three-dimensional load bearing and permeability behavior of crushed salt, a systematized laboratory program was developed within the framework of the joint project KOMPASS (compaction of crushed salt for the safe containment), with the aim of ensuring an isolated recording of individual processes and influencing factors on the compaction behavior. Based on this, triaxial long-term compaction tests, TUC-V2 and TUC-V4, with a test duration of 750 and 180 d, respectively, were carried out within the framework of the joint project KOMPASS and of the follow-up project KOMPASS II. Both tests, but especially TUC-V2 with its 2-year duration, represent a sequence of several loading phases for separate analysis of the effects of individual influencing factors on the compaction behavior of crushed salt. By integrating several loading phases in one long-term test each, it was possible, on the one hand, to eliminate the scattering of the material behavior that would have been expected if several individual tests had been carried out as an alternative and, on the other hand, to provide metrological evidence of the range of validity of the compaction behavior as a function of individual influencing factors for a comparatively wide range of different porosities in each case. The computational reanalysis of the long-term tests opens up the possibility of validating and strengthening the currently available constitutive model approaches with regard to their ability to influence several parameters on the compaction behavior, while eliminating the scatter band of the material behavior. The improvement of the existing constitutive model approaches up to the sufficient reproduction of the measurement results equals an increase in the validation status or the credibility of the constitutive models or, vice versa, a reduction in the uncertainties remaining due to (not yet) validated model assumptions. Within the framework of the KOMPASS II joint project, a benchmark was carried out against the background outlined above for the comparative analysis of the constitutive models currently available to the project partners for depicting the compaction behavior of crushed salt with regard to their ability to computationally represent the measurement results generated within the TUC-V2 experiment. Specifically, the focus is on constitutive model functions that control the viscous compaction and shear deformation behavior and, within these functions, the influencing factors of mean stress, deviatoric stress, and temperature, which were recorded by laboratory tests for medium ranges of porosities from ≈ 16 % to very low porosities of ≈ 2.5 %. Within the framework of the continuation of the investigations planned under the acronym MEASURES (Multi-scale Experimental and numerical Analysis of crushed Salt material Used as engineered backfill for a nuclear waste REpository in rock Salt), it is intended to continue the benchmark study with a more detailed investigation of the influence of the deviatoric stress, which includes considering the data from TUC-V4. It is also intended to supplement the laboratory data base with further experiments by (a) investigations on the compaction behavior in the range of high-to-medium porosities and (b) investigations on the influence of the moisture content on the compaction capability (to be performed with KOMPASS reference material).

Desorption Electrospray Ionization Mass Spectrometry: 20 Years.

ConspectusMass spectrometry (MS) is one of the most widely used technologies in the chemical sciences. With applications spanning the monitoring of reaction products, the identification of disease biomarkers, and the measurement of thermodynamic parameters and aspects of structural biology, MS is well established as a universal analytical tool applicable to small compounds as well as large molecular complexes. Regardless of the application, the generation of gas-phase ions from neutral compounds is a key step in any MS experiment. However, this ionization step was for many years limited to high-energy approaches that required gas-phase analytes and thus it was restricted to volatile samples. Over the last few decades, new methodologies have been developed to address this limitation and facilitate ionization of biological molecules. Electrospray ionization (ESI) is the most broadly used of these methods, as it facilitates the ionization of intact polar compounds from solution.Twenty years ago, our group reported a new ionization method that uses a charged solvent spray to impact a surface, generating ions from objects rather than just solutions and doing so directly in the ambient environment with no vacuum requirements and little to no sample preparation. This method was termed desorption electrospray ionization (DESI), and it initiated a new field that would come to be known as ambient mass spectrometry. The simplicity and wide applicability of the DESI technology─and the tens of ambient ionization methods developed subsequently─revolutionized the MS analysis of complex materials for their organic components, especially for in situ applications.This Account describes the history of DESI, starting with the development of the technique from early electrosonic spray ionization (ESSI) experimental observations as well as the studies leading to the understanding of its mechanism as a "droplet pick-up" phenomenon involving sequential events (i.e., thin film formation, solid-liquid extraction, secondary droplet generation, and ESI-like ionization from these droplets). We also overview the developments and applications of the technology that have been demonstrated by our group during the last two decades. In particular, we describe (i) the use of DESI for tissue imaging, one of its more significant applications to date, and its extension to intraoperative clinical diagnosis; (ii) the integration of the technology with portable instrumentation for in situ analysis, especially when coupled with tandem mass spectrometry (MS/MS); (iii) the use of DESI microdroplets as microvessels to accelerate organic reactions by orders of magnitude compared to those in bulk solution; and (iv) the combination of all these capabilities for automated high-throughput experiments aimed at accelerating drug discovery.

Guided analysis of ambient ionization mass spectrometry data with the MQ Assistant.

Guided analysis of ambient ionization mass spectrometry data with the MQ Assistant.

Disk Wind–Driven Expanding Radio-emitting Shell in Tidal Disruption Events

We study the evolution of a nonrelativistically expanding thin shell in radio-emitting tidal disruption events (TDEs) based on a one-dimensional spherically symmetric model considering the effect of both a time-dependent mass-loss rate of the disk wind and the ambient mass distribution. The analytical solutions are derived in two extreme limits; one is the approximate solution near the origin in the form of the Taylor series, and the other is the asymptotic solution in which the ambient matter is dominant far away from the origin. Our numerical solutions are confirmed to agree with the respective analytical solutions. We find that no simple power law of the time solution exists in early to middle times because the mass-loss rate varies over time, affecting the shell dynamics. We also discuss the application of our model to the observed radio-emitting TDE, AT 2019dsg.

Explosives removal and quantification using porous adsorbents based on poly(2-oxazoline)s with various degree of functionalization

Polymeric porous adsorbents are reported for removal of explosives, namely picric acid, 1,3,5-trinitro-1,3,5-triazinane (RDX), and pentaerythritol tetranitrate (PETN) and their subsequent quantification using direct analysis with ambient plasma mass spectrometry. The adsorbents are obtained by functionalization of short-chain poly(2-oxazoline)s with methyl ester side chains using 4-(aminomethyl)pyridine with a degree of functionalization equal to 0, 5, 10, and 20%. The subsequent step consist of cross-linking using a high internal phase emulsion procedure by further side-chain amidation with diethylenetriamine as crosslinker. Picric acid, RDX, and PETN were chosen as the model compounds as they belong to three different groups of explosives, in particular nitroaromatics, nitroamines, and nitrate esters, respectively. The adsorption isotherms, kinetics, as well as the influence of pH and temperature on the adsorption process was investigated. The porous adsorbents showed the highest maximum adsorption capacity towards picric acid, reaching 334 mg g−1, while PETN (80 mg g−1) and RDX (17.4 mg g−1) were less efficiently adsorbed. Subsequent quantification of the adsorbed explosives is performed by a specially designed ambient mass spectrometry setup equipped with a thermal heater. The obtained limits of detection were found to be 20-times improved compared to direct analysis of analyte solutions. The effectiveness of the proposed analytical setup is confirmed by successful quantification of the explosives in river water samples. The research clearly shows that functional porous adsorbents coupled directly with ambient mass spectrometry can be used for rapid quantification of explosives, which can be, e.g., used for tracking illegal manufacturing sites of these compounds.