Thermal Desorption Method Research Articles

Superior Monitoring of Chemical Exposure Using Nanoconfinement Technology.

Military personnel are exposed to a broad range of potentially toxic compounds that can affect their health. These hazards are unpredictable because military service occurs in a wide array of uncontrolled environments. Therefore, a novel sorbent was developed that allows the fabrication of lightweight personal samplers that are both capable of sorbing an extremely wide range of organic chemical types and able to stabilize reactive compounds. OSU-6, a nanoporous silica, was provided by XploSafe LLC. The sorption capacity for several volatile organic compounds, the temperatures required for thermal desorption of adsorbed compounds, and the sampling rates for targeted analytes were determined. The uptake capacity was found to be on average 1.5 g/g of sorbent. Analytes were not only held tightly but also could be desorbed upon heating the sorbate to temperatures below 150°C. Sampling rates for volatile organic compound by an OSU-6 sampler badge were on average, 5.7 times higher than those for a commercially available activated carbon badge. Theoretical calculations showed that sorption of volatile organic compounds on the surface of the tightly curved pore walls in OSU-6 is because of exceptionally strong cumulative addition of Van der Waals forces. Analytes could readily be analyzed by either solvent extraction or thermal desorption gas chromatography/mass spectrometry techniques. Excellent sampling rates, high concentrations of analytes in the OSU-6 sorbent matrix, and high desorption efficiencies (recoveries) were obtained using the thermal desorption method. The performance of the OSU-6 sorbent makes it highly capable of meeting the need for personal samplers that enable Individual Longitudinal Exposure Records development. It can adsorb an extremely wide array of different volatile organic compounds, it can stabilize reactive compounds, it has high sampling rates coupled with high capacity that provide both sensitivity and resistance to saturation, and it is unique in being very amenable to thermal desorption in combination with having strong sorbate binding and high capacity and surface area.

Challenges and Strategies of Chemical Analysis of Drugs of Abuse and Explosives by Mass Spectrometry.

In analytical science, mass spectrometry (MS) is known as a “gold analytical tool” because of its unique character of providing the direct molecular structural information of the relevant analyte molecules. Therefore, MS technique has widely been used in all branches of chemistry along with in proteomics, metabolomics, genomics, lipidomics, environmental monitoring etc. Mass spectrometry-based methods are very much needed for fast and reliable detection and quantification of drugs of abuse and explosives in order to provide fingerprint information for criminal investigation as well as for public security and safety at public places, respectively. Most of the compounds exist as their neutral form in nature except proteins, peptides, nucleic acids that are in ionic forms intrinsically. In MS, ion source is the heart of the MS that is used for ionizing the electrically neutral molecules. Performance of MS in terms of sensitivity and selectivity depends mainly on the efficiency of the ionization source. Accordingly, much attention has been paid to develop efficient ion sources for a wide range of compounds. Unfortunately, none of the commercial ion sources can be used for ionization of different types of compounds. Moreover, in MS, analyte molecules must be released into the gaseous phase and then ionize by using a suitable ion source for detection/quantification. Under these circumstances, fabrication of new ambient ion source and ultrasonic cutter blade-based non-thermal and thermal desorption methods have been taken into account. In this paper, challenges and strategies of mass spectrometry analysis of the drugs of abuse and explosives through fabrication of ambient ionization sources and new desorption methods for non-volatile compounds have been described. We will focus the literature progress mostly in the last decade and present our views for the future study.

Thermal desorption part 2: applications in analytical measurement.

The past 30 years have seen increasing availability of methods and equipment using thermal desorption for the measurement of airborne substances. These methods offer excellent sensitivity and are well-suited to automation and, in particular, diffusive sampling, a sampling technique which is both easier to use and less obtrusive than pumped sampling. With advances in equipment, thermal desorption is being used in an increasingly wide variety of applications. The capabilities and limitations of thermal desorption equipment and measurement methods were the subject of AMC Technical Brief No. 97. This supplementary Technical Brief aims to illustrate the uses and applications of thermal desorption methods in analytical measurement.

In English

The aim of the work is synthesis and study on the properties of polyfunctional magnetosensitive nanocomposites (NC) and target-directed magnetic fluids (MF) based on physiological solution (PS), magnetite, gemcitabine (GEM) and HER2 antibodies (AB), promising for use in targeted antitumor therapy against MDA-MB-231 aggressive tumor cells of triple-negative human breast cancer (BC) with high proliferative and metastatic activity. The specific surface area (Ssp) of samples was determined by the method of thermal desorption of nitrogen using a device KELVIN 1042 of “COSTECH Instruments”. The size of nanoparticles (NP) has been estimated by the formula DBET = 6/(ρSBET), where ρ is the density of NC particle, SBET is the value of the specific surface area calculated by the polymolecular adsorption theory of Brunauer, Emmett and Teller (BET). The surface condition of nanodispersed samples was studied by IR spectroscopy (“Perkin Elmer” Fourier spectrometer, a model 1720X). To calculate the concentration of hydroxyl groups on the surface of nanostructures, the method of differential thermal analysis was used in combination with differential thermogravimetric analysis. The thermograms were recorded using a derivatograph Q-1500D of MOM firm (Hungary) in the temperature range of 20–1000 °C at a heating rate of 10 deg/min. X-ray phase analysis of nanostructures was performed using a diffractometer DRON-4-07 (CuKα radiation with a nickel filter in a reflected beam, the Bragg-Brentano focusing). The size and shape of NP were determined by electron microscopy (a transmission electron microscope (TEM) JEM-2100F (Japan)). The hysteresis loops of the magnetic moment of the samples were measured using a laboratory vibration magnetometer of Foner type at room temperature. Measurement of optical density, absorption spectra and GEM concentration in solutions was performed by spectrophotometric analysis (Spectrometer Lambda 35 UV/Vis Perkin Elmer Instruments). The amount of adsorbed substance on the surface of magnetite was determined using a spectrophotometer at λ = 268 nm from a calibration graph. The thickness of the adsorbed layer of GEM in the composition of Fe3O4@GEM NC was determined by magnetic granulometry. To study the direct cytotoxic/cytostatic effect of a series of experimental samples of MF based on PS, Fe3O4 NP, GEM, HER2 AB, as well as MF components in mono- or complex use, onto MDA-MB-231 cells in vitro, IC50 index was determined. MF were synthesized on the basis of single-domain Fe3O4 and PS, stabilized with sodium oleate (Ol.Na) and polyethylene glycol (PEG), containing GEM and HER2 (Fe3O4@GEM/Ol.Na/PEG/HER2+PS). The cytotoxic/cytostatic activity of MF against MDA-MB-231 cells was studied. It was found that as a result of application of synthesized MF composed of Fe3O4@GEM/Ol.Na/PEG/HER2+PS at the concentration of magnetite of 0.05 mg/mL, GEM - 0.004 mg/mL and HER2 AB - 0.013 μg/mL, a synergistic effect arose, with reduction of the amount of viable BC cells to 51 %. It has been proved that when using MF based on targeted Fe3O4/GEM/HER2 complex, the increased antitumor efficacy is observed compared to traditional use of the drug GEM, with a significant reduction (by four times) of its dose. The high cytotoxic/cytostatic activity of Fe3O4/GEM/HER2 complexes is explained by the fact that endogenous iron metabolism disorders play a significant role in the mechanisms of realization of the apoptotic program under the influence of nanocomposite. Thus, when the nanocomposite system contains Fe3O4/GEM/HER2 complexes in MDA-MB-231 cells, a significant increase is observed in the level of “free iron”, which favours formation of reactive oxygen species and causes oxidative stress (Fenton reaction). The consequences of oxidative stress are induction of apoptosis, enhancement of lipid peroxidation processes, as well as structural and functional rearrangement of biological membranes. The prospects have been shown of further studies of Fe3O4@GEM/Ol.Na/PEG/HER2+PS MF in order to create on their basis a magnetically carried remedy for use in targeted antitumor therapy.

In Ukrainian

Studying interaction of zinc (II) with silica and alumina-silica surfaces is important for several reasons. From a practical point of view, it is carried out in the framework of the creation of a medicinal product, the ingredients of which are, in particular, silica(alumina)containing sorbent and zinc compound; from a theoretical point of view, it is a search for the adsorption patterns on the mentioned surfaces in a series of d-elements with a close electronic structure (zinc, copper, nickel, cadmium, etc.). In addition, it is advisable to supplement the experimental adsorption data with the results of quantum chemical simulation of the structure and formation energy of zinc (II) complexes with active surface centers. Adsorption of Zn 2+ ions from a neutral aqueous solution on silica and alumina-silica materials was studied by means of the method of adsorption isotherm. The specific surface of the materials was determined by method of thermal desorption of argon. Quantum chemical analysis of the structure and energy of formation of the hydrated zinc sulfate ion pair on silica and alumina-silica surfaces was performed by means of Hartree-Fock-Roothaan method with extended basis set 6‑31++G(d,p). According to the magnitude of adsorption (A) of zinc, the test materials are divided into three groups: 1) enterosgel, kaolin, nanosilica A-300 and polymethylsiloxane, for which А max is from 0.15 to 0.3 mg/g; 2) Syloid® 244 FP, KG-60 and KG-40, aminopropylaerosil, smectite (А max from 1.2 to 12.0 mg/g); 3) zeolites NaA-TK-1173 and NaX (А max more than 30 mg/g). It is concluded that the high adsorption activity of zinc(II) is primarily due to the presence of developed porous structure. The most probable places of interaction between hydrated zinc ions and hydroxyl group of silica and alumina-silica surfaces are determined by means of quantum chemical simulation. The pK Me values have been calculated of ion exchange of silica surface when interacting with Zn 2+ cations.

Physical-chemical predictors of soil pollution in the megapolis

The problem of quantitative assessment of soil pollution of the capital metropolis by controlling physical-chemical factors of solid and liquid phases of soil is investigated. The metals were used as an integral indicator of pollution taking into account the mass fraction and the variation of soil bulk density. Multiple regression (R2=0.91-0.95) of layered heavy metals, as well as accumulation of biophilic elements of the exchange fund from two main predictors – dispersion (effective specific surface area of solid phase, determined by the original thermal desorption method) and pH of salt extract was revealed.

Cobalt catalyst for steam reforming of ethanol–Insights into the promotional role of potassium

The promotional effect of potassium doping on the ESR performance of the CoZn|α-Al2O3 catalyst was thoroughly investigated in the context of its impact on the selectivity and stability of the catalyst, and discussed in terms of cobalt dispersion, oxidation state, cobalt-alumina interactions, catalyst acidity, and the deactivation resistance of the catalyst. The potassium slightly inhibited the cobalt reducibility (XPS, TPR, STEM/EELS), significantly increased the surface concentration and the strength of Lewis sites (FT-IR), enhancing the selectivity to hydrogen. The surface state of potassium at various stages of the catalyst evolution was examined with a species resolved thermal alkali desorption (SR-TAD) method. These studies revealed a pronounced migration of K from the cobalt nanograins towards the alumina support upon the activation and during the ESR processes. Potassium stabilizes the high dispersion of cobalt crystallites and prevents their detachment from the surface and subsequent encapsulation by the growing carbon deposit.

Studying glauconite of the bakchar deposit (Western Siberia) as a prospective sorbent for heavy metals

Glauconite is one of natural clay minerals that are low-cost and readily available. Its specific characters, including potassium cations activity, layered structure and absorption capacity, explain the comprehensive interest to this mineral. It is especially prospective in regard of water treatment. Glauconite composition depends on the formation conditions, which lead to different sorption properties. Here we studied the sorption parameters and physical characteristic of unique glauconite of the Bakchar deposit by mean of granulometric analysis, electromagnetic separation, X-ray fluorescence analysis, inductively coupled plasma-mass spectroscopy, petrographic studies, scanning electron microscopy, X-ray diffraction analysis, nitrogen thermal desorption method, inversion voltammetry. Finally, we tested this mineral as a sorbent. The studied glauconitic concentrate has the best comparative sorption properties. Results show that glauconite of the Bakchar deposit is a cheap and prospective sorbent for heavy metals.

Deconvolution of FIGAERO–CIMS thermal desorption profiles using positive matrix factorisation to identify chemical and physical processes during particle evaporation

Abstract. The measurements of aerosol particles with a filter inlet for gases and aerosols (FIGAERO) together with a chemical ionisation mass spectrometer (CIMS) yield the overall chemical composition of the particle phase. In addition, the thermal desorption profiles obtained for each detected ion composition contain information about the volatility of the detected compounds, which is an important property for understanding many physical properties like gas–particle partitioning. We coupled this thermal desorption method with isothermal evaporation prior to the sample collection to investigate the chemical composition changes during isothermal particle evaporation and particulate-water-driven chemical reactions in α-pinene secondary organic aerosol (SOA) of three different oxidative states. The thermal desorption profiles of all detected elemental compositions were then analysed with positive matrix factorisation (PMF) to identify the drivers of the chemical composition changes observed during isothermal evaporation. The keys to this analysis were to use the error matrix as a tool to weight the parts of the data carrying most information (i.e. the peak area of each thermogram) and to run PMF on a combined data set of multiple thermograms from different experiments to enable a direct comparison of the individual factors between separate measurements. The PMF was able to identify instrument background factors and separate them from the part of the data containing particle desorption information. Additionally, PMF allowed us to separate the direct desorption of compounds detected at a specific elemental composition from other signals with the same composition that stem from the thermal decomposition of thermally instable compounds with lower volatility. For each SOA type, 7–9 factors were needed to explain the observed thermogram behaviour. The contribution of the factors depended on the prior isothermal evaporation. Decreased contributions from the factors with the lowest desorption temperatures were observed with increasing isothermal evaporation time. Thus, the factors identified by PMF could be interpreted as volatility classes. The composition changes in the particles due to isothermal evaporation could be attributed to the removal of volatile factors with very little change in the desorption profiles of the individual factors (i.e. in the respective temperatures of peak desorption, Tmax). When aqueous-phase reactions took place, PMF was able to identify a new factor that directly identified the ions affected by the chemical processes. We conducted a PMF analysis of the FIGAERO–CIMS thermal desorption data for the first time using laboratory-generated SOA particles. But this method can be applied to, for example, ambient FIGAERO–CIMS measurements as well. There, the PMF analysis of the thermal desorption data identifies organic aerosol (OA) sources (such as biomass burning or oxidation of different precursors) and types, e.g. hydrocarbon-like (HOA) or oxygenated organic aerosol (OOA). This information could also be obtained with the traditional approach, namely the PMF analysis of the mass spectra data integrated for each thermogram. But only our method can also obtain the volatility information for each OA source and type. Additionally, we can identify the contribution of thermal decomposition to the overall signal.

0450 Screening Method for Obstructive Sleep Apnea Syndrome by Patients’ Exhalant with TD-GC-MS System

Abstract Introduction Human exhaled breath test is getting more important for non-invasive health monitoring and detecting method nowadays. The diagnosis of obstructive sleep apnea syndrome (OSAS) is often difficult to be confirmed from the daytime presentation and usually need the overnight polysomnography. The methods for OSAS screening are therefore potentials for the clinical practice in the near future. Methods In this research, a method of thermal desorption (TD) tendon with gas chromatography-mass spectrometry (GC-MS) system has been developed for screeing of OSAS patients. We detected the volatile organic compounds (VOCs) from the special designed experimental bags which collected exhaled gas. Then we compared the VOCs from normal control and OSAS group in order to find out the biomarkers which could be used to screen OSAS patients. Furthermore, the Reliable Number(N) was used to see how often the VOC identified in all the experients in OSAS group and was defined as the times of a single VOC identified devided by the times of total experiment in a single OSAS patient. Results While the reliable number been set as ≥50%, we found 8 VOC markers, including Pentane and Cyclopentyl acetylene, appeared more often in OSAS patients. When we raise N to ≥70%, we have only 3 markers remaining. Conclusion Based on this result, we utilize the artificial intelligence method, deep learning, to figure out whether the peak intensity of different biomarkers are related to the severity of OSAS. Support Thanks for Da-Jeng Yao Lab’s support

Very low concentration adsorption isotherms of trichloroethylene on common building materials

Building materials that are found in the indoor environment can play an important role in determining indoor air quality. Previous studies have recognized that building materials are potential sinks/sources of indoor volatile organic compounds (VOCs), but their uptake under extremely low concentrations has not been extensively studied. This study has characterized the capacities of various building materials for adsorption of trichloroethylene (TCE), which is a contaminant of significant concern in vapor intrusion scenarios. The capacities of more than 20 building materials were established at a TCE concentration of 1.12 ppbv (and for selected materials at concentrations up to 12.5 ppbv). This was achieved using a thermal desorption method. Room temperature isotherms for glass wool, polyethylene, nylon carpet, drywall, printer paper, leather, and cinderblock were measured. The results showed that the sorptive capacities of the building materials were at nanograms per gram levels; cinderblock had the largest sorption capacity among all the building materials tested and this is believed to indicate that solid carbon content of materials plays a significant role during the sorption process. TCE desorption from selected building materials was also investigated at room temperature and 100 °C.

ФУНКЦИОНАЛЬНЫЕ НАНОСТРУКТУРИРОВАННЫЕ МАТЕРИАЛЫ НА ОСНОВЕ ДИОКСИДА ТИТАНА ДЛЯ ИСПОЛЬЗОВАНИЯ В ОРТОПЕДИЧЕСКОЙ СТОМАТОЛОГИИ

Subject. The creation of functional ceramic coatings based on titanium dioxide for the manufacture of orthopedic structures, including dental implants and systems for osteosynthesis, helps to prevent possible complications during dental surgical and orthopedic treatment by improving the processes of osseointegration.
 The goal is to develop domestic proprietary technology for producing nanopowders and functional coatings based on titanium dioxide, free of chemical impurities, which can be used in the practice of orthopedic dentistry for the construction of dental and maxillary prostheses, as well as implant systems.
 Methodology. The authors developed and proposed a method for applying to medical devices made of titanium, a nanostructured surface layer of titanium dioxide. To provide an evidence base for the advantages of using the proposed titanium dioxide coating, an experimental study was made of its chemical uniformity and freedom from impurities, as well as an assessment of the adhesion force between the oxide layer deposited by titanium dioxide in the anatase phase and the surface of the titanium support.
 Results. During Raman spectroscopy, titanium dioxide nanopowder did not detect extraneous chemical impurities. According to the results of the method of thermal desorption of nitrogen, the specific surface of the titanium dioxide powder was 67-70 m2 / g, and the average calculated particle size was 20-22 nm. It was shown by optical microscopy that the average thickness of the oxide layer (rutile phase) is 15 ± 5 μm, anatase is 70 ± 10 μm, the adhesion force between the oxide layer (rutile phase) and the titanium base is 6.3 ± 0.1 MPa, at applying anatase - 4.9 ± 0.1 MPa. In the study of the adhesion force of a functional titanium dioxide coating with a titanium base, it was found that the onset of peeling occurs at a load of 8.6 N.
 Conclusions. Studies of a highly developed functional surface layer of nanostructured titanium dioxide indicate the wide possibilities of its use in the practice of a dentist.

Study of the adsorption activity of Fe3O4 synthesized by the solvothermal method in relation to doxorubicin

The solvothermal method synthesized magnetite (Fe3O4) and investigated the processes of immobilization of the cytostatic drug doxorubicin (DOX) on its surface in the medium of 0.9% NaCl solution. The size and morphology (transmission electron microscopy (TEM), crystalline phase magnetite formation [X-ray diffraction analysis (XRD), FTIR spectroscopy] and magnetic properties (vibration magnetometer (VSM), specific surface area and pore size were determined by the method of nitrogen thermal desorption were investigated for the synthesized samples. The adsorption processes were studied and the high adsorption activity of the Fe3O4 nanoparticles (MNPs) surface with respect to DOX was established in the model physiological environment. According to the studies, the adsorption equilibrium time is 45–90 min with up to 80% DOX extraction and maximum adsorption capacity (Amax) 17.5 mg g−1. The analysis of kinetic dependences and DOX adsorption isotherms using mathematical models that take into account the chemical interaction in the system indicates the monomolecular nature of adsorption (Freundlich model). Obtained MNPs can be potentially suitable for oncology applications specifically in the targeted drug delivery and adsorption materials of intracorporeal and extracorporeal detoxification of the body.

Development of Synthetic Magnetic Zeolite Adsorbents and Application to Ammonium Ion Removal

Synthetic magnetic zeolite with Fe3O4 was developed and its adsorption performance of ammonium ions was examined. The influence of pH levels, Fe3O4 content of the magnetic zeolite, magnetization curve of the magnetic zeolite and isotherm curve were examined in batch type experiments. Magnetic zeolite synthesized by a hydrothermal process was observed with less than 12.6 wt% of Fe3O4 content by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. With the optimum pH level around 8, qe decreases linearly with the increase of Fe3O4 content. Additionally, the adsorption isotherm of ammonium ions is approximated by a Langmuir equation when the maximum adsorption was obtained at about 1.60 mmolg−1. Such processes as the substitution and thermal desorption methods were successfully introduced to regenerate the magnetic zeolite saturated by ammonium ions, which is shown to be easily separated by magnetic force. Thus, the magnetic zeolite is a potential adsorbent for the removal of ammonium ions with an easy separation method using a magnetic process.

Practical investigation of direct analysis in real time mass spectrometry for fast screening of explosives

While the direct analysis in real time ionization coupled with mass spectrometry (DART-MS) is viable for the screening of trace explosives, a comprehensive evaluation is needed before its implementation in practice. This work has investigated the effectiveness and limitations of different DART-MS modules for the high-throughput and sensitive detection of nineteen organic explosive residues in four different categories deposited on several substrates. The Quickstrip method was used to optimize DART gas heater temperature as well as dopants. Four sample introducing strategies for DART-MS including transmission, thermal desorption, closed mesh, and direct-insert methods were implemented to analyze liquid and dried samples deposited on different substrates (e.g., fabric, leather, metal, plastic, and synthetic skin). It was found that representative explosives from each category could be detected with nanogram sensitivity and in less than 10 s. Therefore, DART-MS could provide prompt analysis of explosives for forensic applications.

Formula omitted]C signatures of organic aerosols: Measurement method evaluation and application in a source study

Analysis of the stable carbon isotope 13C in organic carbon (OC) can give insight into sources and atmospheric processing of carbonaceous aerosols, provided the 13C source signatures are known. However, only few data on 13C signatures of OC emitted by common sources of carbonaceous aerosol are available in Europe. We present and evaluate an improved version of a measurement method to obtain δ13C signatures on organic aerosols desorbed from filter samples at three different desorption temperatures (200 °C, 350 °C and 650 °C) and apply it in a source study.With our calibration approach, the reproducibility of a L-Valine reference material desorbed at a single temperature step of 650 °C shows a standard deviation of 0.19‰ over a period of more than one year. The average δ13C value for this reference material over 248 measurements is −24.10‰, which shows only a slight bias to the nominal value of −24.03‰. Repeated analysis of ambient filter samples desorbed at three temperature steps show typical standard deviations of about 0.3‰ for all temperature steps (200 °C, 350 °C and 650 °C). Isotopic fractionation due to partial thermal desorption during the individual temperature steps was tested on single compound reference materials. It showed significant isotopic fractionation only at temperature steps, in which a very minor fraction of the compound was desorbed. Possible isotope effects caused by charring of organic material were investigated and found to be not significant.The thermal desorption method was applied to various source filter samples from the region of Naples, Italy. We analyzed two different biomass burning sources, exhaust from a city bus and traffic emissions collected in a tunnel and compared these to ambient filter samples from the same region. δ13C signatures of the total OC show values in a narrow range of about −28‰ to −26‰ for all sources, which does not allow a source apportionment only based on 13C. Nevertheless, the results add information to a source inventory of δ13C, where information of 13C in organic aerosol from specific emission sources are rare. City bus emissions show little variation of δ13C over the temperature steps, whereas biomass burning aerosol is enriched in 13C for OC desorbed at 650 °C. For PM10 samples in the urban tunnel an enrichment in δ13C at the 650 °C temperature steps was observed, which is likely caused by the contribution of carbonate carbon to the carbonaceous material desorbed at this temperature step.

Improvement of quantification and identification of atmospheric reactive mercury

The mercury (Hg) research community is in need of a method to quantify reactive, gaseous oxidized, and particulate-bound Hg compounds. The University of Nevada, Reno-Reactive Mercury Active System (UNR-RMAS) was designed to quantify reactive Hg, as well as identify compounds present in the atmosphere. This system has undergone significant improvements and is now designated as UNR-RMAS 2.0. The system physical design, flow management, and sample analytical methods have been improved. A new sample manifold increased reliability and consistency of air flow. The thermal desorption method for identification of gaseous oxidized Hg compounds was improved with respect to temporal resolution and temperature management. A statistical method was developed that allows for quantifying reactive Hg (RM) compounds. In addition, analyses of anions on nylon membranes was investigated as means of understanding air mass chemistry and potential RM compounds. The results of these improvements are demonstrated through comparison of a year of UNR-RMAS 2.0 sample data collected in 2018–2019 with that collected in 2014–2015. Implemented changes resulted in improved sample replication and resolution of RM quantification and speciation.

Solvent assisted thermal desorption for the on-site detection of illegal drugs by a miniature ion trap mass spectrometer

Schematic diagram of the SFTDPI-ITMS (synchronized flash-thermal-desorption purging and ion injection ion trap mass spectrometer).

Thermal Desorption Technique for Analysis of Aerosolized Methylchloroisothiazolinone/Methylisothiazolinone (CMIT/MIT) in Inhalation Toxicity Testing.

When assessing the inhalation toxicity of diverse inhalable substances, a first step is accurate quantitative analysis. In this study, we developed a method for the quantitative analysis of methylisothiazolinone (MIT) and methylchloroisothiazolinone (CMIT), main components in humidifier disinfectants. A simple thermal desorption (TD) method was used to analyze the CMIT/MIT. Using this method, sample loss during aerosolization was minimized compared with other more complicated pretreatment methods, like solvent absorption and extraction (SV). The results of the TD and SV methods were compared to determine the optimal analytical system for CMIT/MIT analysis. In both methods, the concentration of MIT increased systematically with increasing the CMIT/MIT aerosol concentration (R2>0.98). The MIT contents in the aerosol given by the two analytical methods were somewhat similar (MIT content=1.52% (sample solution), 1.43% (TD) and 1.18% (SV)). In contrast, the measured CMIT content in the aerosol was different depending on the type of pretreatment used. The CMIT content was 2.90% for the TD method, while that for the solvent method recorded 0.75% (CMIT content of the sample solution=4.66%). We confirmed that the sample loss of the CMIT with high reactivity occurred in the complicated sampling and pretreatment steps of the SV method.

Assessment of thermal desorption method application for determination of the saturation characteristics along borehole

Assessment of thermal desorption method application for determination of the saturation characteristics along borehole