Direct Thermal Desorption Research Articles

Analysis of nitrogen-containing rocket fuel transformation products in loamy soil by thermal desorption gas chromatography-tandem mass spectrometry.

Unsymmetrical dimethylhydrazine (UDMH) based rocket fuel, when released into the soil, undergoes oxidative transformations to form a variety of toxic nitrogen-containing products (TPs). Loamy soils containing aluminosilicates (clay) are capable of strong binding and retention of UDMH TPs due to a combination of polar sorption and cation-exchange properties, posing challenges for their extraction and quantification. To overcome this problem, the present study proposes direct thermal desorption (TD) of analytes from loam facilitated by the addition of modifiers competing with UDMH TPs for sorption centers and ensuring their conversion into molecular form. Among tested additives, the mixture of potassium chloride and hydroxide demonstrated the best performance and provided recoveries of the most UDMH TPs exceeding 70% under optimized TD conditions (200°C, 30min). The online combination of TD with gas chromatography-tandem mass spectrometry allowed for the development of a method for the determination of 15 UDMH TPs in loamy soils with limits of detection in the range of 0.2-15µg/kg. The use of matrix-matched calibration and deuterated internal standards ensured high accuracy (80%-100%) and precision (relative standard deviation<18%) of the analysis. The developed method was validated and successfully tested in the analyses of real loamy soil samples polluted with rocket fuel.

Profiling of Organosulfur Compounds in Onions: A Comparative Study between LC-HRMS and DTD-GC-MS

Onions are known not only for their culinary importance but also for their nutritional and health-promoting properties. Both properties are closely linked to their content of organosulfur compounds, which account for up to 5% of the dry weight of an onion. Given the importance of these compounds, suitable analytical methods are required for their study. Two techniques should be highlighted in this context: gas chromatography coupled to mass spectrometry (GC-MS), and liquid chromatography coupled to mass spectrometry (LC-MS). In this study, eight different onion varieties were analyzed using two distinct analytical techniques: direct thermal desorption–gas chromatography–mass spectrometry (DTD-GC-MS) and high-resolution mass spectrometry (HRMS) on an LC-ESI-QqTOF instrument. Each method identified different organosulfur compounds, with LC-HRMS targeting 15 non-volatile compounds, such as cysteine sulfoxides, and GC-MS targeting 18 volatiles, such as disulfides and trisulfides. The results obtained were studied using Pearson correlations and principal component analysis. No precise correlation was found between the initial organosulfur compounds in onions and their hydrolysates. Consequently, although GC is one of the most employed techniques in the scientific literature, the use of LC-HRMS or a combination of both techniques may offer a more comprehensive and accurate description of the metabolomic profile of onions.

Measuring aliphatic hydrocarbons in sediments by direct thermal desorption-gas chromatography-mass spectrometry: Matrix effects and quantification challenges

Direct sample introduction thermal desorption (TD) coupled to GC–MS was investigated for the analysis of paraffinic hydrocarbons (HCs) from polluted sediments. TD-GC–MS is sometimes used for analysing paraffinic HCs from atmospheric particles but rarely for their direct desorption from sediments. So, the new TD methodology, applied to sediments, required development, optimization and validation. A definitive screening experimental design was performed to discriminate the critical factors on TD efficiency, from model sediments containing various organic matter (OM) amounts. Low molecular weight HCs had extraction behaviours markedly different from high molecular ones (HMW-HCs), but a compromise was found using very few sediment amount (5 mg), high temperature rate (55 °C min−1) and final temperature (350 °C). Linear HCs (n-C10 to n-C40) could be quantified using the matrix-matched calibration method, with very low detection limits (3.8–13.4 ng). The amount of the overall paraffinic alkanes was also determined as a sum of unresolved components between predefined equivalent carbon ranges. The developed solventless methodology was compared to an optimized solvent microwave assisted extraction (MAE). Matrix effects could be higher for TD compared to MAE but it depended on sediment matrix. When matrix effect was strong, particularly on HMW-HCs signal depletion, a dilution with pure non-porous sand was favourable for accurate quantification. The sum of resolved and unresolved HCs gave comparable results between MAE and TD extractions, with an exception of alkanes greater than C30 which were less quantitatively extracted via TD. However, TD-GC–MS was more sensitive than MAE-GC–MS. So TD-GC–MS is useful for analyzing sediments containing a great range of paraffinic HCs (C9-C34) and it has the advantages of being fully automated, with few sample preparation and operator intervention, using very low amounts of solvent, and generating few wastes.

Impact of diluents on the calibration of direct dynamic thermal desorption prior to gas chromatography

A thermal desorber (TD) can be used in different ways to introduce samples in a gas chromatographic (GC) system. Besides its conventional use where the collected analytes are released from the sorbent in the sample tube, direct dynamic desorption (DDD) is an interesting option where a solid sample is put directly in the TD tube. However, since no sorbent is used for the sample, proper calibration is not straightforward. This issue was investigated in the present work using offline liquid calibration (OLC) and inline liquid calibration (ILC). Unexpectedly, ILC yielded a lower response than OLC. This could be related to the adsorption kinetics of the analytes and water on the cold trap of the TD. More insight was gained performing double injection ILC experiments with toluene as diluent for the analytes and injecting water before or after the toluene solution. This revealed a clear influence of the diluent. The influence of water was further explored applying two cold trap temperatures (4 °C and −30 °C). Inserting a LiCl trap in the TD tube to capture the water was found to be an effective solution for the problem. Finally, quantitative aspects of this approach were demonstrated.

Direct quantification of 1,1-dimethylhydrazine transformation products in sandy soil by thermal desorption gas chromatography – Tandem mass spectrometry

The use of rocket propellants based on unsymmetrical dimethylhydrazine (UDMH) in launch vehicles and boosters poses a threat to the environment due to the release of UDMH into soils and its subsequent transformation into a variety of nitrogen-containing compounds, including toxic and carcinogenic ones. The present proof-of-concept study proposes a novel approach to screening and simultaneous determination of a wide range of nitrogen-containing UDMH transformation products in soils, based on direct thermal desorption (TD) as a solvent-free sample extraction technique coupled with GC–MS/MS analysis.Optimal TD conditions consisting of the incubation of 5 mg sample at 300 °C for 30 min, allowed attaining high recoveries (80–100 %) for the most tested compounds and developing the method for quantification of fifteen acyclic and heterocyclic UDMH transformation products in sandy soil with LODs of 0.3–7.8 µg kg−1. The matrix matched calibration and introduction of the internal standard (pyridine‑d5) ensured high accuracy (75–100 %) and precision (RSD < 15 %) of the analysis. Along with high sensitivity and accuracy, the main advantages of the developed method are exceptional simplicity of sample preparation, low amount of toxic sample, high automation degree, and environmental friendliness.The developed method was successfully tested in the analysis of seven real soil samples taken from the Baikonur cosmodrome operational zone (Kazakhstan). The use of TD-GC–MS analysis in full spectrum scanning mode allowed for tentative identification of 62 UDMH transformation products including several compounds not yet described in the literature.

A comparative study on flavor trapping techniques from the viewpoint of odorants of hot-pressed rapeseed oil.

Rapeseed oil, as one of the three major vegetable oils in the world, its matrix effect makes the decoding flavor a challenge. Solid-phase microextraction (SPME), SPME-Arrow, headspace stir bar sorptive extraction (HSSE), direct thermal desorption (DTD), and solvent-assisted flavor evaporation (SAFE) were compared based on the odorants in hot-pressed rapeseed oil. Besides, methodological validation for 31 aroma standards was conducted to compare reliability and robustness of these approaches. DTD showed the largest proportion of acids, while the other techniques extracted a majority of nitriles. The highest number of odorants was detected by SAFE (31), followed by HSSE (30), SPME-Arrow (30), SPME (24), and DTD (14). SPME-Arrow showed the best performance in linearity, recovery, and reproducibility followed by SPME, HSSE, DTD, and SAFE. Results reveal the advantages and limitations of diverse methodologies and provide valuable insights for the selection of extraction methods in an oil matrix and flavor decoding.

Year-round measurement of atmospheric volatile organic compounds using sequential sampling in Dronning Maud Land, East-Antarctica

Antarctica is considered the most pristine environment on Earth but is also characterized by its unique conditions such as the strong polar vortex and extreme cold. A detailed understanding of volatile organic compounds (VOCs) and the atmospheric oxidation reactions they undergo is essential to document biogeochemical cycles and to better understand their impact on radiative forcing. This research aims to provide a unique dataset of oxygenated (O)VOCs occurring in the Antarctic troposphere and provide insights into their temporal behavior. A home-made sequential sorbent tube auto sampler was deployed at the atmospheric observatory of the Princess Elisabeth station (71.95° S, 23.35° E, 1390 m asl) to collect 20 samples during the period from December 2019 to October 2020. The samples were analyzed consecutively by TD-GC-MS followed by direct thermal desorption of samples in a high-resolution PTR-Qi-TOFMS.Concentrations of 70 VOCs allocated to 4 different chemical groups (halogenated compounds, non-aromatic hydrocarbons, sulfur-containing compounds, and oxygenated aromatic and non-aromatic compounds) were determined. The results show temporal patterns for compounds such as bromoform (14 ± 6 ng/m3) and OVOCs such as furaldehyde (24 ± 9 ng/m³), amongst others, which are attributed to the seasonality of atmospheric conditions. Products of the atmospheric oxidation process show linear correlation indicating their mutual relationship and association with a common parent compound.The usage of an autonomous autosampler in the extreme conditions of Antarctica was demonstrated and proved to be a powerful tool in the sampling of air in such a remote location. The novel approach of using two analytical techniques boasts increased sensitivity and a broad range of compounds that can be detected, yielding the first dataset of its kind for Antarctica.

17 What’s in the Air We Breathe? Chemical Fingerprinting of Organic Species in Pm2.5 By Td-Gc×Gc-Tof Ms

Abstract The issue of urban air quality has received increased attention in recent years due to increased awareness of the potential health risks associated with particulate matter (PM) concentrations. Airborne particulate matter is composed of solid and/or liquid materials of various sizes, but the fine particles with diameters of &amp;lt;2.5 μm (so-called PM2.5) are of most concern, as long-term exposure to PM2.5 is thought to have the biggest impact on public health. PM2.5 consists of a wide range of components, from both primary emissions (e.g. vehicle exhausts or forest fires) and secondary reactions (i.e. compounds formed in the atmosphere by chemical reactions). It is important to have robust analysis of PM2.5 as the composition can give an indication of its source. PM2.5 is typically trapped onto quartz fibre filters and the semi-volatile organic compounds (SVOCs) are extracted using a solvent. Direct thermal desorption (TD) of the filter avoids this time-consuming sample preparation, for simple, yet sensitive, analysis of particulate matter. However, their identification and quantitation remains a challenge due to sample complexity. Analysts may attempt to address this using longer columns and/or slower oven temperature ramps, but this inevitably leads to longer analysis times. In recent years, the complexity of such samples has been revealed using the improved separation of comprehensive two-dimensional GC coupled with time-of-flight mass spectrometry (GC×GC–TOF MS). Here, we demonstrate the enhanced performance of a TD-GC×GC–TOF MS through analysis of a number of real-world PM2.5 filters.

Application of Direct Thermal Desorption-Gas Chromatography-Mass Spectrometry for Determination of Volatile and Semi-Volatile Organosulfur Compounds in Onions: A Novel Analytical Approach.

The population is now more aware of their diets due to the connection between food and general health. Onions (Allium cepa L.), common vegetables that are minimally processed and grown locally, are known for their health-promoting properties. The organosulfur compounds present in onions have powerful antioxidant properties and may decrease the likelihood of developing certain disorders. It is vital to employ an optimum approach with the best qualities for studying the target compounds to undertake a thorough analysis of these compounds. In this study, the use of a direct thermal desorption-gas chromatography-mass spectrometry method with a Box-Behnken design and multi-response optimization is proposed. Direct thermal desorption is an environmentally friendly technique that eliminates the use of solvents and requires no prior preparation of the sample. To the author's knowledge, this methodology has not been previously used to study the organosulfur compounds in onions. Likewise, the optimal conditions for pre-extraction and post-analysis of organosulfur compounds were as follows: 46 mg of onion in the tube, a desorption heat of 205 °C for 960 s, and a trap heat of 267 °C for 180 s. The repeatability and intermediate precision of the method were evaluated by conducting 27 tests over three consecutive days. The results obtained for all compounds studied revealed CV values ranging from 1.8% to 9.9%. The major compound reported in onions was 2,4-dimethyl-thiophene, representing 19.4% of the total area of sulfur compounds. The propanethial S-oxide, the principal compound responsible for the tear factor, accounted for 4.5% of the total area.

Method comparison of sample pretreatment and discovery of differential compositions of natural flavors and fragrances for quality analysis by using chemometric tools

Natural flavors and fragrances or their extracts have been widely used in a large variety of areas, including food, cosmetic, and tobacco industrial processes, among others. The compositions and intrinsic attributes of flavors and fragrances were related to many factors, such as species, geographical origin, planting environment, storage condition, processing method, and so on. This not only increased the difficulty in analyzing the product quality of flavors and fragrances, but also challenged the idea of “quality-by-design (QbD)”. This work proposed an integrated strategy for precise discovery of differential compounds among different classes and subsequent quality analysis of complex samples through flavors and fragrances used in tobacco industry as examples. Three pretreatment methods were first inspected to effectively characterize the sample compositions, including direct injection (DI), thermal desorption (TD), and stir bar sorptive extraction (SBSE)-TD, coupled with gas chromatography-mass spectrometry (GC–MS) analysis to obtain characteristic information of samples of flavors and fragrances. Then, principal component analysis (PCA) was applied to discover the relation and difference between chromatographic fingerprints and peak table data once significant components were recognized in a holistic manner. Model population analysis (MPA) was then used to quantitatively extract the characteristic chemicals representing the quality differences among different classes of samples. Some differential marker compounds were discovered for difference analysis, including benzyl alcohol, latin acid, l-menthol acid, decanoic acid ethyl ester, vanillin, trans-o-coumaric acid, benzyl benzoate, and so on. Furthermore, partial least squares-discriminant analysis (PLS-DA) and support vector machine (SVM) were respectively applied to construct multivariate models for evaluation of quality differences and variations. It was found that the accuracy attains to 100% for sample classification. With the help of optimal sample pretreatment technique and chemometric methods, the strategy for quality analysis and difference discovery proposed in this work can be widely delivered to more areas of complex plants with good interpretability and high accuracy.

A Methodology for Assessing Pollution Off-Gassing of Museum Construction Materials Using a Pyrolysis Microfurnace

Museum professionals must ensure that protective enclosures for artworks do not in fact cause damage to the objects within due to pollution off-gassing from the container’s components. Ideally, all materials used in proximity to artworks should be assessed for their potential to emit harmful volatiles. The standard approach used in the museum field, known as the Oddy test, requires significant effort and time and can produce unreliable results if not conducted by a trained staff member, all of which reduce the likelihood that proper vetting will be rigorously employed. This paper reports a methodology utilizing a microfurnace pyrolyzer coupled to a gas chromatograph with a mass spectrometer to optimize these assessments and produce actionable results with minimal time and expense. Simple confirmatory chemical tests augment the direct thermal desorption (DTD) experiment, and as a last resort, time-consuming accelerated aging tests are utilized if deemed necessary to eliminate or decide between options when a non-polluting material is not available. The successes and challenges of this developing protocol are highlighted for the planning of a recent non-traditional, multisensory exhibition, THE LUME Indianapolis, with its inaugural digital experience featuring the works of Vincent van Gogh at the Indianapolis Museum of Art at Newfields.

Pre-Drying of Chlorine-Organic-Contaminated Soil in a Rotary Dryer for Energy Efficient Thermal Remediation.

In response to the current problem of the high energy consumption of direct thermal desorption systems when treating soils with a high moisture content, we propose using the waste heat of the system to pre-dry soil to reduce its moisture. Taking chlorine-organic-contaminated soil as an object, an experimental study on the drying and pollutant desorption characteristics of soil in an indirect rotary dryer was carried out. The results show that the non-isothermal drying process was divided into warm-up and falling rate periods, and no constant period was observed. The higher the rotation speed, the lower the soil outlet temperature and the higher the drying tail gas temperature. Soil outlet and dry tail gas temperatures were lower for soils with a higher moisture content. Benzene and cis-1,2-dichloroethylene are easily desorbed. Therefore, the disposal of dry tail gas should be determined according to the type and concentration of soil pollutants present. The volumetric heat transfer coefficient was found to be 85-100 W m-3 °C-1, which provides a key parameter for the size design of a rotary dryer.

Enhancing low-temperature thermal remediation of petroleum sludge by solvent deasphalting.

Thermal treatment is a promising technique for treating petroleum sludge (PS). However, asphaltenes as a recalcitrant fraction of PS induce strong bounding between petroleum and minerals, and therefore lead to the need for high temperature and hence high energy consumption in thermal treatment of PS. In this study, a novel method combining a deasphalting pretreatment of PS with low-temperature thermal desorption (LTTD) was developed. The efficiency of deasphalting was found to be positively correlated to the ability of n-alkanes and asphaltene dispersants in dispersing asphaltenes. In treating six different kinds of PS, the residual oil contents were all below 2.5% after the deasphalting alone. Compared with direct thermal desorption at 600°C for 1h, dodecyl benzene sulfonic acid (DBSA)-assisted heptane deasphalting made thermal desorption at 350°C for 1h sufficient to treat these APS. The residual oil content of sludge after LTTD is lower than 0.45%. FT-IR, Raman spectra and XPS analysis confirmed that the carbon residue in APS after LTTD is primarily graphite state, which is extremely stable and does not migrate to the surrounding environment as compared with the crude oil in the APS. Hence, solvent deasphalting results in effective treatment of PS by LTTD, while the solvent can be recycled by distillation and crude oil recovered as value-added petroleum resource. The LTTD represents therefore a novel green strategy for treating PS and resource utilization.

A Comprehensive Evaluation Method for Soil Remediation Technology Selection: Case Study of Ex Situ Thermal Desorption.

Quantitative evaluation of different contaminated soil remediation technologies in multiple dimensions is beneficial for the optimization and comparative selection of technology. Ex situ thermal desorption is widely used in remediation of organic contaminated soil due to its excellent removal effect and short engineering period. In this study, a comprehensive evaluation method of soil remediation technology, covering 20 indicators in five dimensions, was developed. It includes the steps of constructing an indicator system, accounting for the indicator, normalization, determining weights by analytic hierarchy process, and comprehensive evaluation. Three ex situ thermal desorption technology—direct thermal desorption, indirect thermal desorption, and indirect thermal heap—in China were selected for the model validation. The results showed that the direct thermal desorption had the highest economic and social indicator scores of 0.068 and 0.028, respectively. The indirect thermal desorption had the highest technical and environmental indicator scores of 0.118 and 0.427, respectively. The indirect thermal heap had the highest resource indicator score of 0.175. With balanced performance in five dimensions, the indirect thermal desorption had the highest comprehensive score of 0.707, which is 1.6 and 1.4 times higher than the direct thermal desorption and indirect thermal heap, respectively. The comprehensive evaluation method analyzed and compared the characteristics of the ex situ thermal desorption technology from different perspectives, such as specific indicators, multiple dimensions, and single comprehensive values. It provided a novel evaluation approach for the sustainable development and application of soil remediation technology.

Personal External Exposomes from Around the World

BACKGROUND AND AIM: Industrial advances have led to a plethora of anthropogenic chemicals in our air, water, and soil. Exposures to a subset of these chemicals can lead to illnesses including respiratory illnesses, auto-immune disorders, inhibited immune response, and various cancers. Most studies focus on particulate matter or a select set of chemicals, missing chemicals of potential concern. Therefore, we have developed a personal exposure monitoring technology and workflow to comprehensively determine airborne chemical exposures of concern in populations across the globe. METHODS: Polydimethylsiloxane (PDMS) passive samplers placed in wristbands were deployed in South Africa, China, United States, Canada, and India, both in rural and urban regions. Samplers were shipped to Yale University and analyzed by direct thermal desorption gas-chromatography high-resolution mass spectrometry using a Q-Exactive orbitrap mass spectrometer. A software was developed to rank suspect screening annotations in terms of confidence, normalize for batch effects, filter out chemicals from background contamination, and remove redundant chemical annotations. Furthermore, a workflow implementing tools on the US EPA CompTox Chemicals Dashboard and prototype Hazard Comparison Dashboard was developed to automatically determine chemicals of most concern from a health perspective. RESULTS:Unique chemicals of concern, including pesticides used for malaria control in South Africa and for household pest control in China, fungicides deployed in the United States, and anti-microbial agents found in all populations, were determined. Participants were likely inhaling some of these chemicals, which poses health concerns. Chemical exposures were dynamic, with seasonal variation predominating any other factor among studies in different locations. CONCLUSIONS:We are finding that people around the world, from children in rural South African villages to the elderly in Chinese metropolis, to college students at Yale, are inhaling chemicals of concern, including biocides. These chemical exposures are dynamic, with season seeming to have the greatest influence on exposure profiles. KEYWORDS: Air pollution, external exposome, exposure assessment, omics technologies, mixtures, pesticides

Cross Platform Analysis of Volatile Organic Compounds Using Selected Ion Flow Tube and Proton-Transfer-Reaction Mass Spectrometry.

Volatile breath metabolites serve as potential disease biomarkers. Online mass spectrometry (MS) presents real-time quantification of breath volatile organic compounds (VOCs). The study aims to assess the relationship between two online analytical mass spectrometry techniques in the quantification of target breath metabolites: selected ion flow tube mass spectrometry (SIFT-MS) and proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS). The two following techniques were employed: (i) direct injection with bag sampling using SIFT-MS and PTR-ToF-MS and (ii) direct injection and thermal desorption (TD) tube comparison using PTR-ToF-MS. The concentration of abundant breath metabolites, acetone and isoprene, demonstrated a strong positive linear correlation between both mass spectrometry techniques (r = 0.97, r = 0.89, respectively; p < 0.001) and between direct injection and TD tube (r = 0.97, r = 0.92, respectively; p < 0.001) breath sampling techniques. This was reflected for the majority of short chain fatty acids and alcohols tested (r > 0.80, p < 0.001). Analyte concentrations were notably higher with the direct injection of a sampling bag compared to the TD method. All metabolites produced a high degree of agreement in the detection range of VOCs between SIFT-MS and PTR-ToF-MS, with the majority of compounds falling within 95% of the limits of agreement with Bland-Altman analysis. The cross platform analysis of exhaled breath demonstrates strong positive correlation coefficients, linear regression, and agreement in target metabolite detection rates between both breath sampling techniques. The study demonstrates the transferability of using data outputs between SIFT-MS and PTR-ToF-MS. It supports the implementation of a TD platform in multi-site studies for breath biomarker research in order to facilitate sample transport between clinics and the laboratory.

Profiling of volatile substances by direct thermal desorption gas chromatography high-resolution mass spectrometry for flagging a characterising flavour in cigarette tobacco

This paper describes an analytical method that supports the implementation of articles 9 and 10 of the WHO Framework Convention on Tobacco Control (FCTC) regarding the provisions on the reduction of the palatability and attractiveness of tobacco products regarding flavour ingredients. This study aimed to develop a screening method to identify cigarettes that may have a characterising flavour to support the implementation of the ban of characterising flavours of tobacco products, as laid down in the US and EU law. An analytical method combining direct thermal desorption and GC–QTOF MS was developed for acquiring the profile of volatile and semi-volatile substances in tobacco. A database of flavour additives was created comprising 133 compounds. A group of cigarettes without a declared characterising flavour was used to establish a reference profile of flavouring chemicals commonly present in tobacco products. A reference profile was modelled both by the means of principal component analysis (PCA) and based on the calculation of threshold values specified as 95th percentile of measured compounds’ relative responses. Cigarettes and roll-your-own tobacco labelled as flavoured were analysed to evaluate the discrimination power of the method. A constructed model of the reference cigarettes allowed the differentiation of the flavoured tobacco products from the reference group. The method allows drawing conclusions on the chemical profiles of flavour constituents of tobacco products at even sensorial subliminal concentration levels and is suitable for both the initial screening of products on the market for characterising flavours and for confirmatory purposes after sensory analysis.Graphical abstract

Nanomechanical sampling of material for nanoscale mass spectrometry chemical analysis.

The ability to spatially resolve the chemical distribution of compounds on a surface is important in many applications ranging from biological to material science. To this extent, we have recently introduced a hybrid atomic force microscopy (AFM)-mass spectrometry (MS) system for direct thermal desorption and pyrolysis of material with nanoscale chemical resolution. However, spatially resolved direct surface heating using local thermal desorption becomes challenging on material surfaces with low melting points, because the material will undergo a melting phase transition due to heat dissipation prior to onset of thermal desorption. Therefore, we developed an approach using mechanical sampling and collection of surface materials on an AFM cantilever probe tip for real-time analysis directly from the AFM tip. This approach allows for material to be concentrated directly onto the probe for subsequent MS analysis. We evaluate the performance metrics of the technique and demonstrate localized MS sampling from a candelilla wax matrix containing UV stabilizers avobenzone and oxinoxate from areas down to 250nm × 250nm. Overall, this approach removes heat dissipation into the bulk material allowing for a faster desorption and concentration of the gas phase analyte from a single heating pulse enabling higher signal levels from a given amount of material in a single sampling spot.Graphical abstract.

In situ generated ionic liquid and dispersive liquid-phase microextraction to determine chlorobenzenes in environmental samples by gas chromatography-mass spectrometry

An in situ generated ionic liquid dispersive liquid-phase microextraction procedure (IL-DLPME) is proposed for the preconcentration of ten chlorobenzene compounds (CBs). Direct microvial insert thermal desorption allowed the direct analysis of the IL extract by gas chromatography with mass spectrometry (GC–MS). The developed procedure was applied to the analysis of water and soil samples. An ultrasound assisted extraction (UAE) stage was applied to isolate the analytes from the soil matrices into an ammonium acetate buffer solution, before the preconcentration stage. Several factors affecting microextraction efficiency (volume of ionic components used in the extractant phase and the volume and salt content of the aqueous phase), and the thermal desorption step (desorption time and temperature, and gas flow rate) were studied. Quantification of the water samples was carried out against aqueous standards, while in the case of soils the standard additions method was used, taking into consideration the detected matrix effect. Detection limits in the 0.5–7.2 ng L−1 and 8.4–252 ng kg−1 ranges, depending on the analyte, were obtained for waters and soils, respectively. The accuracy of the method was checked using a certified reference material and by recovery studies. Concentrations in the 2.7–256 ng L−1 and 1.5–50 ng g−1 ranges were obtained for some CBs in waters and soils, respectively.

Assessing the Suitability of Unplasticized Poly(Vinyl Chloride) for Museum Showcase Construction

ABSTRACT Rigid, unplasticized poly(vinyl chloride) (PVC-U) sheet products were evaluated comprehensively for the first time with regard to their use in museum showcase construction. The compositions of numerous name brand products (Sintra, Forex, Komatex, Komacel, Celtec, Ex-cel FF, PALIGHT, and ePVC) have been determined using pyrolysis-gas chromatography-mass spectrometry, while their volatile emissions were assessed using modified Oddy tests as well as direct thermal desorption chromatography at elevated temperatures. Despite frequently passing the aggressive conditions of the Oddy test, most premium quality brands were found to release 2-ethylhexyl thioglycolate (2-EHTG), a sulfur-bearing byproduct of a heat stabilizing additive. Importantly, only the economy versions of PVC-U analyzed in this study (Komacel and ePVC) did not contain the sulfur compound. This volatile thioglycolate was shown here using molecular spectroscopies to deposit on and react with copper and silver surfaces. Similarly, lead white pigmented watercolor was blackened by the thioglycolate. Based on these results, alternative materials are recommended for display cases that will contain sulfide-sensitive materials like metals.