Vapor Samples Research Articles

A device to generate multi-concentration tritiated water vapor

Access to a gas tritium source with controlled concentrations is the key to calibrating tritium measurement instruments. In this study, a method of generating multi-concentration tritiated water vapor based on a closed circulation loop is outlined. The method produces tritiated water vapor by a bubbling process, the operational parameters for achieving the saturated bubbling process were determined through simulation. The temperature dependence of the isotope fractionation coefficient has been established through experimental tests. In order to avoid leakage of tritium and contamination of laboratory environment, tritiated water vapor generator was plugged into a closed loop and tested. Two tritiated water standard samples with known concentrations were used to produce 20 tritiated water vapor samples at 10 different temperatures, where the experimental results were in good agreement with the empirical formula. Based on the experimental results, the model for a non-closed loop tritiated water vapor generation has been modified, and the formula for multi-concentration tritiated water vapor generation based on a closed loop is established.

The sampling and removal of tritiated water vapor in Taiwan research reactor

The Taiwan Research Reactor (TRR) is a research facility in Taiwan. TRR is a heavy water reactor designed based on the National Research Experiment (NRX) with output thermal power 40 MW. On January 3, 1973, it reach criticality. TRR had been operated for 15 years and was permanently shut down in early 1988. TRR uses heavy water moderation and light water cooling. Hence, some tritium was created when deuterium captures a neutron. The inside of the Calandria has been washed with clean water after shutdown. After draining the water in the interior, it is inevitable that some residual water would remain at the bottom of the Calandria. Air sampling and analysis techniques were employed to detect and quantify tritiated water vapor. The investigation of tritiated water vapor in the TRR Calandria proved potential tritium contamination risks. Adopting the vapor condensation drying technique proved effective in removing tritiated water vapor from the TRR Calandria. After the removal of tritiated water vapor, the air in the Calandria no longer contains rich concentration of tritiated water vapor. That will help to ensure a safe environment for decommissioning operations.

B-229 Extraction-free Nucleic Acid Sample Preparation from Inhibitor Rich Samples via Hyperbaric Heating

Abstract Background Extraction-based nucleic acid sample preparation for PCR is limited by long processing times, liquid transfers, cost, and storage requirements. Extraction-free approaches enable streamlined sample prep but are severely impacted by inhibitors present in biological sample matrices. We previously reported the use of Hyperbaric Heating (HBH) for effective organism lysis and demonstrate here its effectiveness to prepare nucleic acids for PCR from various inhibitor-rich sample matrix types. Methods HBH exposes the sample to high temperature/high pressure environment for a short duration. This process effectively lyses organisms and denatures inhibitors within seconds. Samples are sealed within a pressure-tight metallic vessel, then rapidly heated using magnetic induction. Within the sealed metallic vessel, vaporization of the aqueous sample raises the internal pressure, enabling an internal temperature higher than 100°C. Proprietary sample processing beads containing chelating agents and other proteins protect nucleic acids from fragmentation during heating. Results The efficacy of HBH for PCR amplification was tested against commercial kits and extraction-free methods. HBH treatment of nasal swab samples spiked with inactivated SARS-CoV-2 elicited detection down to 125 viral copies/mL. Viruses such as RSV and Influenza spiked in nasal swab samples demonstrated comparable PCR results as extraction prepped samples. HBH treatment of microbe samples, including Candida albicans spiked in urine and Bacillus subtilis spiked in serum, had comparable PCR threshold cycles as microbe specific DNA extraction methods (Table 1). Conclusions HBH is a generalizable extraction-free nucleic acid sample prep technology affording detection capabilities comparable to commercial sample prep methods. We demonstrated the use of HBH sample prep for detection of several infectious microorganisms in common biological matrices (nasal swab, serum, urine) without additional sample purification. With its ease of use, speed, and lower cost, HBH will be a key tool in applications where nucleic acid amplification is pivotal for diagnostic and research use.

Development of an Ultrasonic Nebulization System for an Inverse Low Temperature Plasma Ionization Source.

An effective nebulization and evaporation of a liquid sample, like in liquid chromatography, mass spectrometry (LC-MS) couplings, is an essential requirement for the ionization of analyte molecules in the gas phase by, for example, atmospheric pressure chemical ionization (APCI) or the novel low temperature plasma (LTP)-based ion source. These LTP-based ion sources have recently gained interest in the field of atmospheric pressure ion sources, as they can cover a wide range of polarity and molecular mass. They can be used in combination with separation techniques like liquid chromatography or used as an ambient ion source. However, commercial nebulizer systems are of course not constructed to fit to home-built LTP-based ion sources, and this was one incentive to develop a new nebulization system. Instead of an atmospheric pressure chemical ionization (APCI) nebulizer, two commercial nebulizers were disassembled and remodeled to be used as nebulizing systems in an LC-MS setup using an LTP-based ion source. Based on these results, a novel nebulizer system was subsequently developed. To further improve the degree of ionization, cones to focus the LC eluent spray on the plasma region, heating applications, and auxiliary nitrogen gas for dispersion of the solvent droplets were implemented. The LOD that could be calculated via the rule of three resulted in an average of 2.0 μg/L for the APCI-nebulizer and 41 μg/L for the USN. Both could be reduced to 1.4 and 18 μg/L, respectively, by using a TPI-configuration instead of an iLTP. The linearity was equally good for both types of nebulization devices. The final nebulizer could also be operated with a high water content and flow rates higher than those of the two previous ones, indicating an important improvement step.

What caused the lag between oxygen-18 and deuterium excess in atmospheric vapor and precipitation during the earlier summer season in southwest China?

A combined interpretation of oxygen-18 (δ18O) and deuterium excess (d-excess) in various archives in the Indian monsoon-dominated region may add value to the isotopic climate significance. Yet, coupling water δ18O and d-excess together is rarely discussed. Here, we present measurements for both δ18O and δ2H in water vapor and precipitation samples collected in the Nujiang River valley, an important moisture corridor for the Indian monsoon in southwestern China, aiming for an improved understanding of the hydrological cycle on seasonal scales. The observation found a significant drop occurred in the earlier summer season for δ18O and d-excess in vapor and precipitation. However, an approximately one-month lag between vapor δ18O and vapor d-excess is observed in seasonal variations, revealing different drivers for the seasonal patterns of vapor d-excess and δ18O. Spatial correlation analysis found that d-excess is mainly modulated by the relative humidity over the core moisture source over the Bay of Bengal (BOB), while the sharp decrease of vapor δ18O corresponds to the onset of the Indian summer monsoon associated with large-scale convective activities, which significantly depleted the vapor heavy isotopes. The finding of the phase difference in the seasonal isotope signals and the underlying mechanism will benefit the study in particularly using both δ18O and d-excess for an improved understanding of the hydrological processes in the Indian monsoon-dominated region, and will provide new insight into studies of paleoclimate rebuilding by using isotope-based proxy as well.

Sensing signal augmentation by flow rate modulation of carrier gas for accurate differentiation of complex odours

ABSTRACT For olfactory sensors, clear differentiation of complex odour samples requires diverse information. To obtain such information, hardware modifications, such as introducing additional channels with different physical/chemical properties, are usually needed. In this study, we present a new approach to augmenting the sensing signals of an olfactory sensor by modulating the flow rate of the carrier gas. The headspace vapour of complex odours is measured using a sensing system of nanomechanical sensor (Membrane-type Surface stress Sensor, MSS). The resulting data set is quantitatively evaluated using the Davies-Bouldin index (DBI) of principal component analysis (PCA). The increasing number of sensing signals obtained at different gas flow rates leads to a decrease in the DBI, achieving better cluster separation between different odours. Such gas flow effects can be attributed to several factors, including the sample evaporation and the equilibrium of the gas-liquid and gas-solid interfaces. Proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS) experiments reveal that the compositions of odour samples vary with the different gas flow rates. It is demonstrated that a simple technique for modulating gas flow rates can significantly improve the differentiation performance of complex odours, providing an additional degree of freedom in olfactory sensing.

Automated compound speciation, cluster analysis, and quantification of organic vapors and aerosols using comprehensive two-dimensional gas chromatography and mass spectrometry

Abstract. The advancement of analytical techniques, such as comprehensive two-dimensional gas chromatography coupled with mass spectrometry (GC×GC–MS), enables the efficient separation of complex organics. Developing innovative methods for data processing and analysis is crucial to unlock the full potential of GC×GC–MS in understanding intricate chemical mixtures. In this study, we proposed an innovative method for the semi-automated identification and quantification of complex organic mixtures using GC×GC–MS. The method was formulated based on self-constructed mass spectrum patterns and the traversal algorithms and was applied to organic vapor and aerosol samples collected from the tailpipe emissions of heavy-duty diesel vehicles and the ambient atmosphere. Thousands of compounds were filtered, speciated, and clustered into 26 categories, including aliphatic and cyclic hydrocarbons, aromatic hydrocarbons, aliphatic oxygenated species, phenols and alkylphenols, and heteroatom-containing species. The identified species accounted for over 80 % of all the eluted chromatographic peaks at the molecular level. A comprehensive analysis of quantification uncertainty was undertaken. Using representative compounds, quantification uncertainties were found to be less than 37.67 %, 22.54 %, and 12.74 % for alkanes, polycyclic aromatic hydrocarbons (PAHs), and alkyl-substituted benzenes, respectively, across the GC×GC space, excluding the first and the last time intervals. From a source apportionment perspective, adamantane was clearly isolated as a potential tracer for heavy-duty diesel vehicle (HDDV) emissions. The systematic distribution of nitrogen-containing compounds in oxidized and reduced valences was discussed, and many of them served as critical tracers for secondary nitrate formation processes. The results highlighted the benefits of developing self-constructed models for the enhanced peak identification, automated cluster analysis, robust uncertainty estimation, and source apportionment and achieving the full potential of GC×GC–MS in atmospheric chemistry.

Effects of Heat Treatment on Anodic Porous Alumina Membranes for Mass Spectrometry

Abstract Desorption ionization using through-hole alumina membrane (DIUTHAME) method is a mass spectrometry imaging (MSI) method that uses an anodic porous alumina membrane (APAM) with an array of submicron-sized through-holes as a surface-assisted laser desorption/ionization (SALDI) substrate. The DIUTHAME method is particularly promising for MSI because it does not generate interfering peaks in the low-molecular-weight region. However, the SALDI effect cannot be obtained if the nanostructures of the substrate are destroyed owing to laser irradiation before sample vaporization. APAMs that maintain their structures after irradiation with a high-intensity laser must be fabricated to realize highly sensitive measurements. In this study, we investigated the role of heat treatment suppressing the laser irradiation induced fracture of APAMs. We found that heat treatment at higher temperatures more effectively suppressed APAM fracture associated with laser irradiation. This result was attributed to the reduction of anion-derived impurities in APAMs upon heat treatment. The resulting heat-treated APAM is expected to serve as a substrate for highly sensitive and robust MSI.

A Finger-Actuated Sample-Dosing Capillary-Driven Microfluidic Device for Loop-Mediated Isothermal Amplification.

Loop-mediated isothermal amplification (LAMP) has attracted significant attention for rapid and accurate point-of-care diagnostics. However, integrating sample introduction, lysis, amplification, and detection steps into an easy-to-use, disposable system has so far been challenging. This has limited the uptake of the technique in practical applications. In this study, we developed a colourimetric one-step LAMP assay that combines thermolysis and LAMP reaction, to detect the SARS-CoV-2 virus in nasopharyngeal swab samples from COVID-19-infected individuals. The limit of detection was 500 copies per reaction at 65 °C for 25 min in reaction tubes. Additionally, we developed a finger-operated capillary-driven microfluidic device with selective PVA coating. This finger-actuated microfluidic device could self-dose the required sample amount for the LAMP reaction and inhibit sample evaporation. Finally, we integrated the LAMP assay into the microfluidic device by short-term pre-storage of the LAMP master mix. Using this device, nasopharyngeal swab samples from COVID-19-infected individuals showed positive results at a reaction time of 35 min at 65 °C. This integrated device may be adapted to detect other RNA viruses of interest rapidly.

Flow analysis-solid phase extraction system and UHPLC-MS/MS analytical methodology for the determination of antiviral drugs in surface water

An automated flow analysis-solid phase extraction (FA-SPE) system and methodology of ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) analysis were developed for the determination of selected antiviral drugs (acyclovir, amantadine, rimantadine, and oseltamivir) in water samples. The proposed FA-SPE approach enables the integration of various extraction stages and elimination of the sample evaporation step and offers individual customisation of SPE parameters, inter alia sample, and eluate flow rate and volume. Using the developed FA-SPE procedure, e.g. a 100-fold preconcentration of the target analytes in 1 h was achieved. A method for chromatographic analysis was also developed to determine the selected antiviral drugs in combination with the use of the FA-SPE system. The developed FA-SPE UHPLC-MS/MS method was validated including the determination of linearity of analytical graphs, limits of detection (5.5–99.9 pg mL−1) and quantification (18.3–329.8 pg mL−1), intra-day (1.8–8.3%) and inter-day (3.0–9.2%) precision, recovery (95.6–105.3%), and matrix effects (− 12.9 to 13.2%). The proposed method was successfully applied to analyse tap, drinking, and river water samples, revealing the presence of amantadine at a concentration of 40.1 pg mL−1 in one sample. The environmental impact of the developed FA-SPE sample preparation procedure was also assessed using the AGREEprep metric tool and compared with five other literature methods, achieving the most sustainable outcome.Graphical abstract

A Simple Water Sample Storage Test for Water Isotope Analysis

Water is pivotal for human societies’ sustainability and resilience. Isotope hydrology and hydrogeology research plays an important role in understanding and managing water resources. Reliable scientific results hinge on high-quality data. Preventing water sample evaporation is essential for accurate isotopic analysis. In this study, the impacts on the quality of isotopic data were tested for the storage of water samples and the repetitive opening of a laboratory reference material (LRM) sub-sample replica during daily operation. Twenty 15 mL water samples were stored in high-density polyethylene (HDPE) bottles at room temperature and humidity to simulate storage conditions. One 60 mL water sample was collected from the same starting batch to simulate the LRM sub-sample. Each 15 mL sample was analysed once over 80 days for the isotopic composition of oxygen (δ18O) and hydrogen (δ2H). The 60 mL sample was repeatedly analysed in the same period. The data were tested to identify shifts in the isotopic composition induced by evaporative processes. The main results of the work are the following: (i) storage of the 15 mL water samples did not cause detectable evaporation in the testing period; (ii) the 60 mL δ18O values showed evidence of evaporation as proved by the positive shift of the isotopic data; (iii) the repetitive opening of the 60 mL sample was the main cause of evaporation; (iv) five openings can already cause detectable isotopic enrichment. Careful manipulation and frequent replacement of the LRM are thus necessary to prevent deterioration of the quality of the analyses.

A new setup for measurements of absolute saturation vapor pressures using a dynamical method: Experimental concept and validation.

We describe a new experimental system for direct measurements of the absolute saturation vapor pressures of liquid or solid samples. The setup allows the isolation of the sample under steady conditions in an ultra-high vacuum chamber, where the measurement of the sample's vapor pressure as a function of its temperature can be performed in a range around room temperature and in a pressure range defined only by the applied absolute pressure sensor. We characterize the setup and illustrate its capability to measure saturation vapor pressures as well as enthalpies of evaporation around room temperature with explicit measurements on four liquid compounds (diethyl phthalate, 1-decanol, 1-heptanol, and 1-hexanol) for which accurate vapor pressures have previously been reported.

Physiological and hygienic assessment of a multilayer set of personal protective equipment against low temperatures made using membrane materials

Introduction. Advanced personal protective equipment (PPE) against low temperatures is a high–tech product created using the latest achievements of science, design designs, ergonomic, aesthetic solutions that determine its thermal protection properties. The use of membrane materials in PPE from low temperatures allows them to combine low weight and high thermal protection properties, low air permeability and sufficient vapor permeability necessary to ensure heat and moisture exchange between humans and the environment. The study aims to determine the thermal protection properties of various sets of multilayer workwear and indicators of heat and moisture exchange of volunteers when modeling professional activity at low air temperature. Materials and methods. The authors have conducted a study in a microclimatic chamber with the participation of six practically healthy male volunteers. The researchers have determined the thermal protection properties of multilayer workwear of various configurations in accordance with GOST R 12.4.185-99 and MUK 4.3.1894-04. As test samples, they have used pipes of three different configurations to protect against low temperatures, wind, water, general industrial pollution and mechanical influences, as well as short-term exposure to open fire. The assessment of heat and moisture exchange indicators of various PPE configurations was carried out by specialists when modeling work activities with measurements of the relative humidity level in the layers of the kits and the level of accumulated moisture in each element of the PPE. Results. The authors have determined the values of thermal insulation of the studied materials and the scope of their application. To assess heat and moisture exchange, two samples of PPE were selected, made using membrane and cotton fabrics with similar thermal insulation values. The analysis of the results of studies of moisture exchange indicators showed a slightly lower efficiency of moisture evaporation of the control sample. The indicator of the relative humidity of the air under the shelter space and between the layers of the package of materials and clothing has shown its informative significance for assessing the effectiveness of moisture transfer from the surface of the human body to the environment. Conclusion. The results of a physiological and hygienic assessment of a set of multilayer clothing made of membrane materials have shown that various combinations of its constituent elements make it possible to create kits that provide adequate protection for an employee in a wide range of air temperatures and wind speeds. The use of membrane materials in combination with structural elements (ventilation openings) provides a more efficient transfer of moisture from the skin surface to the external environment, as evidenced by the values of the relative humidity index of the air under the clothing space and between the layers of clothing. Ethics. The study was approved by the local Ethical committee of the Izmerov Research Institute of Occupational Health (Minutes of the meeting No. 6 dated 07/20/12)

Axial Phenoxylation of Aluminum Phthalocyanines for Improved Cannabinoid Sensitivity in OTFT Sensors.

Cannabis producers, consumers, and regulators need fast, accurate, point-of-use sensors to detect Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) from both liquid and vapor source samples, and phthalocyanine-based organic thin-film transistors (OTFTs) provide a cost-effective solution. Chloro aluminum phthalocyanine (Cl-AlPc) has emerged as a promising material due to its unique coordinating interactions with cannabinoids, allowing for superior sensitivity. This work explores the molecular engineering of AlPc to tune and enhance these interactions, where a series of novel phenxoylated R-AlPcs are synthesized and integrated into OTFTs, which are then exposed to THC and CBD solution and vapor samples. While the R-AlPc substituted molecules have a comparable baseline device performance to Cl-AlPc, their new crystal structures and weakened intermolecular interactions increase sensitivity to THC. Grazing-incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM) are used to investigate this film restructuring, where a significant shift in the crystal structure, grain size, and film roughness is detected for the R-AlPc molecules that do not occur with Cl-AlPc. This significant crystal reorganization and film restructuring are the driving force behind the improved sensitivity to cannabinoids relative to Cl-AlPc and demonstrate that analyte-semiconductor interactions can be enhanced through chemical modification to create more responsive OTFT sensors.

Chemical Characterization of Human Body Odor Headspace Components

This study focused on evaluating human body odor volatiles using a chamber approach. Ten participants were asked to sit inside the chamber for 1 h, while using SPME as the extraction technique for vapor sampling. A total of 105 compounds were detected across participants, with nonanal having the highest frequency. PCA statistical analysis depicted tighter clustering in female whole-body odor profiles when compared to males, thus corroborating gender odor differences. Concurrently, various biospecimens (hand, axillary, breath) from the same participants allowed for a comparison between whole-body and individual biospecimen odor signatures. When comparing whole-body sampling and distinctive biospecimens, nonanal and decanal were the only odor volatiles shared. Statistical clustering depicted higher similarity within the odor profiles of individual biospecimens compared to odor profiles of the whole body, indicating distinctiveness of the odor chemical landscape as a function of sampling region. Overall, this study demonstrated that SPME-GC/MS methodology was successful in the extraction, detection, and identification of previously reported human scent volatiles when employing the human chamber for whole-body sampling. Our presented testing paradigm allows for a direct comparison of odor volatiles across the full body and specific body locations that allows odor markers to be furthered exploited for diagnostic and biological detection contexts.

Real-time monitoring and predictive analysis of VOC flux variations in soil vapor: Integrating PID sensing with machine learning for enhanced vapor intrusion forecasts

In the rapidly evolving domain of vapor intrusion (VI) assessments, traditional methodologies encompass detailed groundwater and soil vapor sampling coupled with comprehensive laboratory measurements. These models, blending empirical data, theoretical equations, and site-specific parameters, evaluate VI risks by considering a spectrum of influential factors, from volatile organic compounds (VOC) concentrations in groundwater to nuanced soil attributes. However, the challenge of variability, influenced by dynamic ambient conditions and intricate soil properties, remains. Our study presents an advanced on-site gas sensing station geared towards real-time VOC flux monitoring, enriched with an array of ambient sensors, and spearheaded by the reliable PID sensor for VOC detection. Integrating this dynamic system with machine learning, we developed predictive models, notably the random forest regression, which boasts an R-squared value exceeding 79 % and mean relative error near 0.25, affirming its capability to predict trichloroethylene (TCE) concentrations in soil vapor accurately. By synergizing real-time monitoring and predictive insights, our methodology refines VI risk assessments, equipping communities with proactive, informed decision-making tools and bolstering environmental safety. Implementing these predictive models can simplify monitoring for residents, reducing dependence on specialized systems. Once proven effective, there's potential to repurpose monitoring stations to other VI-prone regions, expanding their reach and benefit. The developed model can leverage weather forecasting data to predict and provide alerts for future VOC events.

Intrinsic Water Transport in Moisture-Capturing Hydrogels.

Moisture-capturing hydrogels have emerged as attractive sorbent materials capable of converting ambient humidity into liquid water. Recent works have demonstrated exceptional water capture capabilities of hydrogels while simultaneously exploring different strategies to accelerate water capture and release. However, on the material level, an understanding of the intrinsic transport properties of moisture-capturing hydrogels is currently missing, which hinders their rational design. In this work, we combine absorption and desorption experiments of macroscopic hydrogel samples in pure vapor with models of water diffusion in the hydrogels to demonstrate the first measurements of the intrinsic water diffusion coefficient in hydrogel-salt composites. Based on these insights, we pattern hydrogels with micropores to significantly decrease the required absorption and desorption times by 19% and 72%, respectively, while reducing the total water capacity of the hydrogel by only 4%. Thereby, we provide an effective strategy toward hydrogel material optimization, with a particular significance in pure-vapor environments.

Gas Chromatographic Determination of Residual Concentrations of a Mixture of Organochlorine Pesticides in Food Products

Purpose of research. The aim of the work is to optimize the conditions for gas chromatographic determination of a mixture of eight organochlorine pesticides: aldrin, hexachlorobenzene, heptachlor, α-hexachlorocyclohexane, γ-hexachlorocyclohexane, dichlorodiphenyltrichloromethylmethane, dichlorodiphenyldichloroethane and dichlorodiphenyldichloroethylene.Methods. For chromatographic studies of organochlorine pesticides we used a Shimadzu GC-2010Plus gas chromatograph (Shimadzu, Japan) equipped with an automatic equilibrium vapor sample dispenser NT200N, electron-capture detector based on 63Ni and quartz capillary nonpolar column "Chromatek" SPB-5 (30 m, 0.32 mm, film thickness on the basis of phenyl(5%) and dimethyl(95%) polysiloxanes 0.5 μm) with an operating temperature range of 60°C 320/340°C. The chromatograms were processed in the application LabSolutions GPC.Results. On the basis of experimentally obtained data the optimal conditions for gas chromatographic determination and separation of eight-component mixture of organochlorine pesticides were selected, namely: the value of mobile phase flow division 1:10, carrier gas flow rate – 1.0 ml/min, two-stage temperature programmable column mode from 160 to 240°C with the rate of increase of 5°C/min. The metrological characteristics of the analysis and validation of the results of the proposed technique with the method of high-performance liquid chromatography were evaluated. Good reproducibility of chromatography results with the possibility of detection of organochlorine pesticides at the level of 10-6 – 10-5 μg/cm3 was proved. Application of Fisher's test has shown absence of significant differences in reproducibility of sampled populations the investigated methods of chromatographic analysis of COPCs are equally accurate. Extraction sample preparation of samples of real objects was proposed, the calculated extraction degrees >84% allow to recommend the technique for quantitative determination of analytes.Conclusion. The method of gas chromatographic analysis was tested for determination of organochlorine pesticides in samples of drinking water and baby puree (Russia) by additive method. Exceeding the norms of residual contents of organochlorine pesticides in the samples of the food products under study was not detected.

Development of a direct PMMA-PCB bonding method for low cost and rapid prototyping of microfluidic-based gas analysers.

Rapid prototyping of microfluidic devices requires low cost materials and simple fabrication methods. PMMA and PCB have been used separately for the fabrication of microfluidic devices in a wide range of applications. Although the combined use of PMMA and PCB can have considerable merits, few works have been reported on the direct bonding of these materials. In this work we have investigated the fabrication of microfluidic devices using PMMA and PCB for the analysis of gaseous samples. In order to yield a reliable direct bonding method, four parameters including temperature, pressure, solvent and patterned interface material were experimentally investigated. Results of testing various prototypes showed that a patterned interface of concentric rectangular copper rings exposed to solvent at room temperature and under moderate pressure provided better adhesion strength, sealing and durability. After successful development of the PMMA-PCB direct bonding process, sample prototypes were designed and fabricated to practically assess the combined advantages of two materials. Presented concepts include implementation of heater on a PCB, array of gas sensors coupled with microchannels, serpentine microchannel and fast evaporation of liquid sample using an SMD resistor. It has been shown that advantages of utilizing PMMA such as fabricating the channel easily and with low cost, can be combined with benefits of a PCB including simple sensor installation and the use of copper tracks and electronic components for gas flow modulation. Moreover, it is possible to implement channel, circuit and other electronic components such as microprocessors on a single device.

Ultraviolet-Visible Absorption Spectroscopy of MoCl5, MoOCl4, and MoO2Cl2 Vapors.

This article reports quantitative absorption spectra for MoCl5, MoOCl4, and MoO2Cl2 in the vapor phase from 45,500 to 15,500 cm-1 (645 to 220 nm). Spectra are obtained in an ultrahigh purity stainless steel vacuum system by rapidly sampling a range of analyte partial pressures. The short measurement times and the differential absorbance method employed here minimize effects from uncontrolled transients such as window deposits. A detailed analysis of replicate measurements and time-resolved spectra shows generally reproducible spectral response from MoCl5 vapors at 120 °C. The presence of HCl and MoOCl4 impurities in the MoCl5 vapor samples is determined to be unlikely based on the analysis of absorbance-pressure curves and spectral peak fitting. Comparison with MoOCl4 and MoO2Cl2 spectra shows a unique spectral fingerprint for MoCl5 at 28,500 cm-1 providing a convenient means of discriminating between MoCl5 and its oxychlorides in the visible wavelengths. Adsorption behavior of MoCl5 on surfaces is also discussed with particular emphasis on the use of MoCl5 as a reactant in vapor phase thin film deposition processes.