Detection Of Benzene Research Articles

A Miniaturized Linear Wire Ion Trap with Electron Ionization and Single Photon Ionization Sources.

A linear wire ion trap (LWIT) with both electron ionization (EI) and single photon ionization (SPI) sources was built. The SPI was provided by a vacuum ultraviolet (VUV) lamp with the ability to softly ionize organic compounds. The VUV lamp was driven by a pulse amplifier, which was controlled by a pulse generator, to avoid the detection of photons during ion detection. Sample gas was introduced through a leak valve, and the pressure in the system is shown to affect the signal-to-noise ratio and resolving power. Under optimized conditions, the limit of detection (LOD) for benzene was 80ppbv using SPI, better than the LOD using EI (137ppbv). System performance was demonstrated by distinguishing compounds in different classes from gasoline. Graphical Abstract ᅟ.

Ultra-selective detection of sub-ppm-level benzene using Pd–SnO2 yolk–shell micro-reactors with a catalytic Co3O4 overlayer for monitoring air quality

Ultra-selective and sensitive detection of benzene was achieved using Pd-loaded SnO2 yolk–shell micro-reactor sensing films coated with a catalytic Co3O4 overlayer.

Investigation of Polymer-Plasticizer Blends as SH-SAW Sensor Coatings for Detection of Benzene in Water with High Sensitivity and Long-Term Stability.

We report the first-ever direct detection of benzene in water at concentrations below 100 ppb (parts per billion) using acoustic wave (specifically, shear-horizontal surface acoustic wave, SH-SAW) sensors with plasticized polymer coatings. Two polymers and two plasticizers were studied as materials for sensor coatings. For each polymer-plasticizer combination, the influence of the mixing ratio of the blend on the sensitivity to benzene was measured and compared to commercially available polymers that were used for BTEX (benzene, toluene, ethylbenzene, and xylene) detection in previous work. After optimizing the coating parameters, the highest sensitivity and lowest detection limit for benzene were found for a 1.25 μm thick sensor coating of 17.5%-by-weight diisooctyl azelate-polystyrene on the tested acoustic wave device. The calculated detection limit was 45 ppb, with actual sensor responses to concentrations down to 65 ppb measured directly. Among the sensor coatings that showed good sensitivity to benzene, the best long-term stability was found for a 1.0 μm thick coating of 23% diisononyl cyclohexane-1,2-dicarboxylate-polystyrene, which was studied here because it is known to show no detectable leaching in water. The present work demonstrates that, by varying type of plasticizer, mixing ratio, and coating thickness, the mechanical and chemical properties of the coatings can be conveniently tailored to maximize analyte sorption and partial chemical selectivity for a given class of analytes as well as to minimize acoustic-wave attenuation in contact with an aqueous phase at the operating frequency of the sensor device.

Preparation and application of a coated-fiber needle extraction device.

In this study, a needle-trap device with fibers coated with a molecularly imprinted polymer was developed for separation. A number of heat-resistant Zylon filaments were longitudinally packed into a glass capillary, followed by coating with a molecularly imprinted polymer. Then, the molecularly imprinted polymer coating was copolymerized and anchored onto the surface of the fibers. The bundle of synthetic fibers coated with the molecularly imprinted polymer was packed into a 21G stainless-steel needle and served as an extraction medium. The coated-fiber needle extraction device was used to extract volatile organic compounds from paints and gasoline effectively. Subsequently, the extracted volatile organic compounds were analyzed by gas chromatography. Calibration curves of gaseous benzene, toluene, ethylbenzene, and o-xylene in the concentration range of 1-250 μg/L were obtained to evaluate the method, acceptable linearity was attended with correlation coefficients above 0.998. The limit of detection of benzene, toluene, ethylbenzene, and o-xylene was 11-20 ng/L using the coated-fiber needle-trap device. The relative standard deviation of needle-to-needle repeatability was less than 8% with an extraction time of 20 min. The loss rates after storage for 3 and 7 days at room temperature were less than 30%.

Improving the analytical performance of ion mobility spectrometer using a non-radioactive electron source

For the ionization of gas mixtures, several ionization sources can be coupled to an ion mobility spectrometer. Radioactive sources, e.g. beta radiators like 63Ni and 3H, are the most commonly used ionization sources. However, due to legal restrictions radioactive ionization sources are not applicable in certain applications. Non-radioactive alternatives are corona discharge ionization sources or photoionization sources. However, using an electron gun allows regulation of ion production rate, ionization time and recombination time by simply changing the operating parameters, which can be utilized to enhance the analytical performance of ion mobility spectrometers. In this work, the impact of an ionization source parameter variation on the ion mobility spectrum is demonstrated. Increasing the ion production rate, the amount of the generated ions increases leading to higher signal intensity while the noise remains constant. Thus, the signal to noise ratio can be increased, leading to better limits of detection. In a next step, the ion production rate is kept constant while the influence of ionization time on the ion mobility spectrum is investigated. It is shown, that varying the ionization time allows the determination of the reaction rate constants as additional information to the ion mobility. Furthermore, we show the prevention of discrimination processes by using short ionization times combined with an increased ion production rate. Thus, the limit of detection for benzene in presence of toluene is improved. Additionally, it is shown that using ion-ion recombination leads to the detection of the ion species with the highest proton affinity at higher recombination times while the low proton affine ions already recombined. Thus, the measurement of the ion mobility spectra at a defined recombination time allows a suppression of disturbing low proton affine substances.

The detection of benzene in Saturn's upper atmosphere

AbstractThe stratosphere of Saturn contains a photochemical haze that appears thicker at the poles and may originate from chemistry driven by the aurora. Models suggest that the formation of hydrocarbon haze is initiated at high altitudes by the production of benzene, which is followed by the formation of heavier ring polycyclic aromatic hydrocarbons. Until now there have been no observations of hydrocarbons or photochemical haze in the production region to constrain these models. We report the first vertical profiles of benzene and constraints on haze opacity in the upper atmosphere of Saturn retrieved from Cassini Ultraviolet Imaging Spectrograph stellar occultations. We detect benzene at several different latitudes and find that the observed abundances of benzene can be produced by solar‐driven ion chemistry that is enhanced at high latitudes in the northern hemisphere during spring. We also detect evidence for condensation and haze at high southern latitudes in the polar night.

Ultra-sensitive benzene detection by a novel approach: Core-shell nanowires combined with the Pd-functionalization

We have realized an excellent selective sensing to benzene (C6H6) by means of using SnO2-ZnO core-shell nanowires functionalized with Pd nanoparticles. We obtained a response of 71 for 100ppb of C6H6, which is the highest response reported thus far. The synergistic effects of variation of SnO2/ZnO potential barriers and chemical sensitization of Pd are responsible for the highest C6H6-sensing performance. These results highlight the potential for using Pd functionalized nanowires as a sensing platform in detecting trace concentrations of benzene, which is applicable in the future sensor, including the disease diagnosis and the environmental monitoring.

Environmental temperature effect on the far-infrared absorption features of aromatic-based Titan's aerosol analogs

Benzene detection has been reported in Titan's atmosphere both in the stratosphere at ppb levels by remote sensing (Coustenis et al., 2007; Vinatier et al., 2007) and in the thermosphere at ppm levels by the Cassini's Ion and Neutral Mass Spectrometer (Waite et al., 2007). This detection supports the idea that aromatic and heteroaromatic reaction pathways may play an important role in Titan's atmospheric chemistry, especially in the formation of aerosols. Indeed, aromatic molecules are easily dissociated by ultraviolet radiation and can therefore contribute significantly to aerosol formation. It has been shown recently that aerosol analogs produced from a gas mixture containing a low concentration of aromatic and/or heteroaromatic molecules (benzene, naphthalene, pyridine, quinoline and isoquinoline) have spectral signatures below 500cm−1, a first step towards reproducing the aerosol spectral features observed by Cassini's Composite InfraRed Spectrometer (CIRS) in the far infrared (Anderson and Samuelson 2011, and references therein). In this work we investigate the influence of environmental temperature on the absorption spectra of such aerosol samples, simulating the temperature range to which aerosols, once formed, are exposed during their transport through Titan's stratosphere. Our results show that environmental temperature does not have any major effect on the spectral shape of these aerosol analogs in the far-infrared, which is consistent with the CIRS observations.

Detection of Benzene and Alkylated Benzene Derivatives in Fuel Contaminated Environments

Reported herein is the sensitive and selective detection of benzene and alkylated benzene derivatives as well as the practical application of this system in the detection of fuel contaminated environments following a March 2015 tanker truck crash at the Bourne Rotary in Bourne, Massachusetts. This detection method relies on the ability of cyclodextrin to promote proximity‐induced fluorescence modulation of a high quantum yield fluorophore, which led to unique modulation responses for each cyclodextrin‐analyte‐fluorophore combination investigated. The measured changes in fluorescence emission were used to generate arrays using linear discriminant analysis to generate unique pattern identifiers for each combination. The method was successful in detecting ppm levels of analytes with 100% success in differentiating analytes in purified buffer solution and 100% success in differentiating between analytes in water samples from three collection locations related to the crash site: downstream, upstream, and directly from the drainage pipe. Notably, this method was successful in generating well‐separated signals for structural isomers of xylene (ortho, meta, para) which is difficult without specialized mass spectrometry‐based techniques. The high selectivity, sensitivity, and broad applicability of this method have significant potential in the detection of aromatic analytes in a wide range of complex environments.

Integrated pre-concentrator gas sensor microsystem for ppb level benzene detection

An integrated microsystem for (indoor) air quality monitoring applications is presented. By combining a gas pre-concentrator based on metal-organic frameworks (MOFs) and a metal oxide semiconductor gas sensor, a device for detecting ppb levels of volatile organic compounds was designed, integrated and tested with benzene as a target gas. Two metal organic frameworks have been characterized for their suitability as gas pre-concentration materials for benzene and toluene using inverse gas chromatography and mass spectrometry measurements in order to obtain breakthrough values for gas adsorption. Both MOFs showed a higher pre-concentration effect compared to Tenax® TA, a state-of-the-art commercial adsorbent material.By depositing a MOF material on a micro hotplate integrated in a package together with a gas sensor, an integrated gas sensor microsystem was realized. This system has been characterized in FEM simulations concerning its gas pre-concentration capabilities and behavior. Test measurements were performed using benzene at concentrations of 10–1000ppb. Both the simulations and the measurements show the suitability of the system design for the task. Significantly increased gas concentrations have been observed during thermal desorption from the pre-concentrator after gas adsorption at a low temperature.

Effect of phytoremediation on concentrations of benzene, toluene, naphthalene, and dissolved oxygen in groundwater at a former manufactured gas plant site, Charleston, South Carolina, USA, 1998–2014

Concentrations of benzene, toluene, naphthalene, and dissolved oxygen in groundwater at a former manufactured gas plant site near Charleston, South Carolina, USA, have been monitored since the installation of a phytoremediation system of hybrid poplar trees in 1998. Between 2000 and 2014, the concentrations of benzene, toluene, and naphthalene (BTN this pathway of uptake by trees was confirmed by the detection of benzene, toluene, and naphthalene in trees during sampling events in 2002, and later in the study in 2012. These data suggest that the phytoremediation system affects the groundwater contaminants on a seasonal basis and, over multiple years, has resulted in a cumulative decrease in dissolved-phase contaminant concentrations in groundwater. The removal of dissolved organic contaminants from the aquifer has resulted in a lower demand on dissolved oxygen supplied by recharge and, as a result, the redox status of the groundwater has changed from anoxic to oxic conditions. This study provides much needed information for water managers and other scientists on the viability of the long-term effectiveness of phytoremediation in decreasing groundwater contaminants and increasing dissolved oxygen at sites contaminated by benzene, toluene, and naphthalene.

Spray Inlet Proton Transfer Reaction Mass Spectrometry (SI-PTR-MS) for Rapid and Sensitive Online Monitoring of Benzene in Water.

Rapid and sensitive monitoring of benzene in water is very important to the health of people and for environmental protection. A novel and online detection method of spray inlet proton transfer reaction mass spectrometry (SI-PTR-MS) was introduced for rapid and sensitive monitoring of trace benzene in water. A spraying extraction system was coupled with the self-developed PTR-MS. The benzene was extracted from the water sample in the spraying extraction system and continuously detected with PTR-MS. The flow of carrier gas and salt concentration in water were optimized to be 50 sccm and 20% (w/v), respectively. The response time and the limit of detection of the SI-PTR-MS for detection of benzene in water were 55 s and 0.14 μg/L at 10 s integration time, respectively. The repeatability of the SI-PTR-MS was evaluated, and the relative standard deviation of five replicate determinations was 4.3%. The SI-PTR-MS system was employed for monitoring benzene in different water matrices, such as tap water, lake water, and wastewater. The results indicated that the online SI-PTR-MS can be used for rapid and sensitive monitoring of trace benzene in water.

Integrated Gas Sensing System of SWCNT and Cellulose Polymer Concentrator for Benzene, Toluene, and Xylenes.

An integrated cellulose polymer concentrator/single-walled carbon nanotube (SWCNT) sensing system is demonstrated to detect benzene, toluene, and xylenes (BTX) vapors. The sensing system consists of functionalized cellulose as a selective concentrator disposed directly on top of a conductive SWCNT sensing layer. Functionalized cellulose concentrator (top layer) selectively adsorbs the target analyte and delivers the concentrated analyte as near as possible to the SWCNT sensing layer (bottom layer), which enables the simultaneous concentrating and sensing within a few seconds. The selectivity can be achieved by functionalizing cellulose acetate with a pentafluorophenylacetyl selector that interacts strongly with the target BTX analytes. A new design of the integrated cellulose concentrator/SWCNT sensing system allows high sensitivity with limits of detection for benzene, toluene, and m-xylene vapors of 55 ppm, 19 ppm, and 14 ppm, respectively, selectivity, and fast responses (<10 s to reach equilibrium), exhibiting the potential ability for on-site, real-time sensing applications. The sensing mechanism involves the selective adsorption of analytes in the concentrator film, which in turn mediates changes in the electronic potentials at the polymer-SWCNT interface and potentially changes in the tunneling barriers between nanotubes.

Triptycene-Roofed Quinoxaline Cavitands for the Supramolecular Detection of BTEX in Air.

Two novel triptycene quinoxaline cavitands (DiTriptyQxCav and MonoTriptyQxCav) have been designed, synthesized, and applied in the supramolecular detection of benzene, toluene, ethylbenzene, and xylenes (BTEX) in air. The complexation properties of the two cavitands towards aromatics in the solid state are strengthened by the presence of the triptycene moieties at the upper rim of the tetraquinoxaline walls, promoting the confinement of the aromatic hydrocarbons within the cavity. The two cavitands were used as fiber coatings for solid-phase microextraction (SPME) BTEX monitoring in air. The best performances in terms of enrichment factors, selectivity, and LOD (limit of detection) values were obtained by using the DiTriptyQxCav coating. The corresponding SPME fiber was successfully tested under real urban monitoring conditions, outperforming the commercial divinylbenzene-Carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fiber in BTEX adsorption.

Concave Cu2O octahedral nanoparticles as an advanced sensing material for benzene (C6H6) and nitrogen dioxide (NO2) detection

We report a facile and efficient method for the synthesis of novel concave Cu2O octahedral nanostructure. The concave Cu2O octahedral nanostructure has an average diameter of 400nm. Moreover, the Cu2O nanorods were also prepared by controlling the hydroxylamine hydrochloride (NH2OH·HCl) concentrations. The concave Cu2O octahedral nanostructures were evaluated as a sensing materials for benzene (C6H6) detection at operating temperature of 230°C and the results reveal that it has excellent sensing dependence to C6H6 concentration changes. Interestingly, The concave Cu2O octahedral nanostructure also has good sensing response to NO2 at relatively low operating temperatures of 50°C with high response of 4.3 and the response and recovery time shorter than 20 and 131s to 20ppm, respectively. The multifunctional concave Cu2O octahedral nanostructures would be promising functional nanomaterials in sensor fields.

Detection of volatile organic compounds released by wood furniture based on a cataluminescence test system.

Wood furniture is an important source of indoor air pollution. To date, the detection of harmful substances in wood furniture has relied on the control of a single formaldehyde component, therefore the detection and evaluation of pollutants released by wood furniture are necessary. A novel method based on a cataluminescence (CTL) sensor system generated on the surface of nano-3TiO2-2BiVO4 was proposed for the simultaneous detection of pollutants released by wood furniture. Formaldehyde and benzene were selected as a model to investigate the CTL-sensing properties of the sensor system. Field emission scanning electronic microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were employed to characterize the as-prepared samples. The results showed that the as-prepared test system exhibited outstanding CTL properties such as stable intensity, a high signal-to-noise ratio, and short response and recovery times. In addition, the limit of detection for formaldehyde and benzene was below the standard permitted concentrations. Moreover, the sensor system showed outstanding selectivity for formaldehyde and benzene compared with eight other common volatile organic compounds (VOCs). The performance of the sensor system will enable furniture VOC limit emissions standards to be promulgated as soon as possible.

Use of radiation sources with mercury isotopes for real-time highly sensitive and selective benzene determination in air and natural gas by differential absorption spectrometry with the direct Zeeman effect

A new analytical portable system is proposed for the direct determination of benzene vapor in the ambient air and natural gas, using differential absorption spectrometry with the direct Zeeman effect and innovative radiation sources: capillary mercury lamps with different isotopic compositions (196Hg, 198Hg, 202Hg, 204Hg, and natural isotopic mixture). Resonance emission of mercury at a wavelength of 254 nm is used as probing radiation. The differential cross section of benzene absorption in dependence on wavelength is determined by scanning of magnetic field. It is found that the sensitivity of benzene detection is enhanced three times using lamp with the mercury isotope 204Hg in comparison with lamp, filled with the natural isotopic mixture. It is experimentally demonstrated that, when benzene content is measured at the Occupational Exposure Limit (3.2 mg/m3 for benzene) level, the interference from SO2, NO2, O3, H2S and toluene can be neglected if concentration of these gases does not exceed corresponding Occupational Exposure Limits. To exclude the mercury effect, filters that absorb mercury and let benzene pass in the gas duct are proposed. Basing on the results of our study, a portable spectrometer is designed with a multipath cell of 960 cm total path length and detection limit 0.5 mg/m3 at 1 s averaging and 0.1 mg/m3 at 30 s averaging. The applications of the designed spectrometer to measuring the benzene concentration in the atmospheric air from a moving vehicle and in natural gas are exemplified.

Study on Effect of Acid and Heat Treatments of Multi-Walled Carbon Nanotubes on Benzene Detection

Effect of acid and heat treatments of multi-walled carbon nanotubes (MWCNTs) on benzene detection was investigated. For acid treatment, MWCNTs were treated by hydrochloric acid (HCl) for 1 h meanwhile other batches of MWCNTs were treated by heating under air ambient at 500°C for 1 h. Pristine, HCl-treated and heat-treated MWCNTs were separately coated with ethyl cellulose (EC) by spin-coating prior to fabrication of three different sensors named as EC/pristine MWCNTs, EC/HCl-MWCNTs and EC/heat-MWCNTs sensors, respectively. Each fabricated sensor was exposed to benzene vapor at room temperature for testing its sensing performance based on an increase in its electrical resistance which was sensitive to benzene vapor. Response of the sensors fabricated from EC/HCl-MWCNTs and EC/heat-MWCNTs were 3.66 and 1.92 times higher than that of EC/pristine MWCNTs, respectively. Sensitivity of all sensors would be attributed to swelling of EC, resulting in loosening of MWCNT network after benzene vapor exposure. In addition, the difference of sensing response of the EC/pristine MWCNTs when compared with those of EC/HCl-MWCNTs and EC/heat-MWCNTs would be ascribed to different crystallinity and functionalization of MWCNTs sidewalls, suggesting that acid and heat treatments of MWCNTs would be promising techniques for improvement of benzene detection.

Potential of ion mobility spectrometry versus FT-MIR and GC-MS to study the evolution of a heat transfer fluid after its heating process in a thermosolar plant

Heat transfer fluid (HTF) is commonly used in heat transfer industrial processes such as those performed in thermosolar plants. Although HTF is thermally stable, the high temperatures used in such plants (around 400°C) and overheating in continuous cycles can alter its composition. The potential changes in its initial composition (biphenyl and diphenyl ether), and the likely production of new compounds, such as benzene and phenol, require using fast-response portable instruments for on-site quality control at thermosolar plants. In this work, the degradation profile of HTF heated for a variable time was for the first time characterized by using two different ion mobility spectrometry (IMS) instruments. The simple one used a UV lamp as ionization source (UV-IMS), whereas the other included a chromatographic column coupled to a tritium source (GC-3H-IMS). Other analytical techniques such as Fourier transform-mid infrared spectroscopy (FT-MIR) and gas chromatography–mass spectrometry (GC-MS) were also used for the same purpose. Based on the results, both IMS instruments can be useful for online quality control of HTF in a thermosolar plant. Thus, the UV-IMS instrument can be used for screening purposes and the GC-3H-IMS instrument for selective detection of benzene and phenol as degradation products.

Humidity independent mass spectrometry for gas phase chemical analysis via ambient proton transfer reaction

In this work, a humidity independent mass spectrometric method was developed for rapid analysis of gas phase chemicals. This method is based upon ambient proton transfer reaction between gas phase chemicals and charged water droplets, in a reaction chamber with nearly saturate humidity under atmospheric pressure. The humidity independent nature enables direct and rapid analysis of raw gas phase samples, avoiding time- and sample-consuming sample pretreatments in conventional mass spectrometry methods to control sample humidity. Acetone, benzene, toluene, ethylbenzene and meta-xylene were used to evaluate the analytical performance of present method. The limits of detection for benzene, toluene, ethylbenzene and meta-xylene are in the range of ∼0.1 to ∼0.3ppbV; that of benzene is well below the present European Union permissible exposure limit for benzene vapor (5μgm−3, ∼1.44ppbV), with linear ranges of approximately two orders of magnitude. The majority of the homemade device contains a stainless steel tube as reaction chamber and an ultrasonic humidifier as the source of charged water droplets, which makes this cheap device easy to assemble and facile to operate. In addition, potential application of this method was illustrated by the real time identification of raw gas phase chemicals released from plants at different physiological stages.