Volatile Organic Compounds In Water Research Articles

In situ growth of silver nanoparticles on polydopamine-coated chalcogenide glass tapered fiber for the highly sensitive detection of volatile organic compounds in water

A high-sensitivity Ge-Sb-Se chalcogenide glass (ChG) tapered fiber (TF) sensor based on a polydopamine (PDA)-silver nanoparticle (AgNP) coating structure is proposed for the first time in this study. The influence of PDA coating thickness on sensitivity to p-xylene aqueous solution is investigated by characterizing the immersion time of TF in the dopamine. Experimental results demonstrate that an increased coating thickness results in higher sensitivity. Based on the reduction of Ag ions by catechol groups in PDA, the optimized PDA-coated TF is exposed to the AgNO3 solution to grow in-situ AgNPs on the coating surface. The existence of AgNPs can introduce effective light coupling between the AgNPs and evanescent waves, enhancing the infrared absorption of the molecules. The sensitivity of the PDA-coated sensor functionalized by AgNPs to detect p-xylene is significantly improved to 4.115E-4 a.u./μg/mL, which is 63 times higher than that of the uncoated sensor. Furthermore, the sensor based on the PDA-AgNP structure exhibits a shorter response time and good practical applicability.

Determination of 9 kinds of volatile halogenated alkane and chlorobenzene compounds in water by gas chromatography-mass spectrometry with purge and trap method

In this study, in the face of water environmental pollution, a more simple and efficient detection method was obtained for simultaneous determination of 9 kinds of volatile halogenated alkane and chlorobenzene compounds in water by PT/GCMS. By optimizing the purge and trap conditions, the optimal experimental conditions were obtained as follows: purge time was 15 min, purge temperature was 35 °C, purge velocity was 40 mL/min, desorption time was 2 min, desorption temperature was 240 °C. The linearity of the method was good, and the correlation coefficients were all greater than 0.999. The minimum detection limit(MDL) of the method was 0.1 μg/L. The average recovery rate ranged from 85.4 %~102.1 % in surface water and drinking water with relative standard deviation (RSD) ranged from 5.3 %-9.2 % in the spiked concentration levels of 5 μg/L and 10 μg/L. This method has the advantages of simple operation, good separation effect, rapid detection, high recovery and good precision, and can simultaneously meet the requirements of 9 kinds of volatile organic compounds detection in drinking water and surface water. This work provides a new method for the detection of volatile organic compounds in water and will have great significance for the detection of water quality.

Determination of Volatile Organic Compounds in Water by Attenuated Total Reflection Infrared Spectroscopy and Diamond-Like Carbon Coated Silicon Wafers

Volatile organic compounds (VOCs) are one of the most commonly detected contaminants in water. The occurrence is mainly in gasoline and other petroleum-based products, fumigants, paints and plastics. Releases into the environment and the widespread use have an impact on the ecosystem such as humans and animals due to their toxicity, mutagenicity, and carcinogenicity. VOCs may persist in groundwater and may enter drinking water supplies. In this paper, a diamond-like carbon (DLC)-coated silicon waveguide in combination with a polymer film (ethylene/propylene copolymer, E/P-co) for enrichment of analytes was investigated to determine its suitability for ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopic detection of VOCs. The DLC film was fluorine-terminated enhancing the adhesion of the hydrophobic polymer to the waveguide surface. The analytes diffuse into the hydrophobic polymer whereas water is excluded from the emanating evanescent field. Therefore, direct detection in aqueous systems is enabled. Nine VOCs, i.e., ethylbenzene (EB), trichloroethylene (TCE), tetrachloroethylene (TeCE), the xylene isomers (p-xylene, pXYL; m-xylene, mXYL; o-xylene, oXYL), naphthalene (NAPH), toluene (TOL), and benzene (BENZ), were evaluated simultaneously qualitatively and quantitatively showing the potential of DLC coatings revealing high sensitivities in the low ppb to ppm concentration range, i.e., 50 ppb for TeCE. To the best of our knowledge, this is the first time of IR spectroscopic detection of VOCs in aqueous solutions using DLC-coated waveguides in combination with a hydrophobic polymer. By utilizing a DLC-coated waveguide, a versatile sensor for real-time monitoring in harsh environments such as effluents, leaking pipelines, and underground storage tanks is feasible due to response times within a few minutes.

Layered double hydroxide/poly(vinylpyrrolidone) coated solid phase microextraction Arrow for the determination of volatile organic compounds in water.

Today, wide variety of adsorbents have been developed for sample pretreatment to concentrate and separate harmful substances. However, only a few solid phase microextraction Arrow adsorbents are commercially available. In this study, we developed a new solid phase microextraction Arrow coating, in which nanosheets layered double hydroxides and poly(vinylpyrrolidone) were utilized as the extraction phase and poly(vinyl chloride) as the adhesive. This new coating entailed higher extraction capacity for several volatile organic compounds (allyl methyl sulfide, methyl propyl sulfide, 3-pentanone, 2-butanone, and methyl isobutyl ketone) compared to the commercial Carboxen 1000/polydimethylsiloxane coating. Fabrication parameters for the coating were optimized and extraction and desorption conditions were investigated. The validation of the new solid phase microextraction Arrow coating was accomplished using water sample spiked with volatile organic compounds. Under the optimal conditions, the limits of quantification for the five volatile organic compounds by the new solid phase microextraction Arrow coating and developed gas chromatography with mass spectrometry method were in the range of 0.2-4.6ng/mL. The proposed method was briefly applied for enrichment of volatile organic compounds in sludge.

便携式GC-MS用于水中挥发性有机物的应急监测

便携式GC-MS用于水中挥发性有机物的应急监测

Enhanced headspace single drop microextraction method using deep eutectic solvent based magnetic bucky gels: Application to the determination of volatile aromatic hydrocarbons in water and urine samples.

A facile headspace single drop microextraction method was developed using deep eutectic solvent-based magnetic bucky gel as the extraction solvent for the first time. The hydrophobic magnetic bucky gel was formed by combining choline chloride/chlorophenol deep eutectic solvent and magnetic multiwalled carbon nanotube nanocomposite. Magnetic susceptibility, high viscosity, high sorbing ability, and tunable extractability of organic analytes are the desirable advantages of the prepared gel. Using a rod magnet as a suspensor in combination with the magnetic susceptibility of the prepared gel resulted in a highly stable droplet. This stable droplet eliminated the possibility of drop dislodgement. The prepared droplet made it possible to complete the extraction process in high temperatures and elevated agitation rates. Furthermore, using larger micro-droplet volumes without any operational problems became possible. These facts resulted in shorter sample preparation time, higher sensitivity of the method, and lower detection limits. Under the optimized conditions, an enrichment factor of 520-587, limit of detection of 0.05-0.90ng/mL, and linearity range of 0.2-2000ng/mL (coefficient of determination=0.9982-0.9995) were obtained. Relative standard deviations were<10%. This method was successfully coupled with gas chromatography and used for the determination of benzene, toluene, ethylbenzene, and xylene isomers as harmful volatile organic compounds in water and urine samples.

Development of Solid Ceramic Dosimeters for the Time-Integrative Passive Sampling of Volatile Organic Compounds in Waters.

Time-integrative passive sampling of volatile organic compounds (VOCs) in water can now be accomplished using a solid ceramic dosimeter. A nonporous ceramic, which excludes the permeation of water, allowing only gas-phase diffusion of VOCs into the resin inside the dosimeter, effectively captured the VOCs. The mass accumulation of 11 VOCs linearly increased with time over a wide range of aqueous-phase concentrations (16.9 to 1100 μg L-1), and the linearity was dependent upon the Henry's constant (H). The average diffusivity of the VOCs in the solid ceramic was 1.46 × 10-10 m2 s-1 at 25 °C, which was 4 orders of magnitude lower than that in air (8.09 × 10-6 m2 s-1). This value was 60% greater than that in the water-permeable porous ceramic (0.92 × 10-10 m2 s-1), suggesting that its mass accumulation could be more effective than that of porous ceramic dosimeters. The mass accumulation of the VOCs in the solid ceramic dosimeter increased in the presence of salt (≥0.1 M) and with increasing temperature (4 to 40 °C) but varied only slightly with dissolved organic matter concentration. The solid ceramic dosimeter was suitable for the field testing and measurement of time-weighted average concentrations of VOC-contaminated waters.

Fe(3)O(4)/polyethylene glycol nanocomposite as a solid-phase microextraction fiber coating for the determination of some volatile organic compounds in water.

A high-performance metal oxide polymer magnetite/polyethylene glycol nanocomposite was prepared and coated in situ on the surface of the optical fiber by sol-gel technology. The magnetite nanoparticles as nanofillers were synthesized by a coprecipitation method and bonded with polyethylene glycol as a polymer. The chemically bonded coating was evaluated for the headspace solid-phase microextraction of some environmentally important volatile organic compounds from aqueous samples in combination with gas chromatography and mass spectrometry. The prepared fiber was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The mass ratio of nanofiller and polymer on the coating extraction efficiency, morphology, and stability were investigated. The parameters affecting the extraction efficiency, including the extraction time and temperature, the ionic strength, desorption temperature, and time were optimized. The sol-gelized fiber showed excellent chemical stability and longer lifespan. It also exhibited high extraction efficiency compared to the two types of commercial fibers. For volatile organic compounds analysis, the new fiber showed low detection limits (0.008-0.063 ng/L) and wide linearity (0.001-450 × 104 ng/L) under the optimized conditions. The repeatability (interday and intraday) and reproducibility were 4.13-10.08 and 5.98-11.61%, and 7.35-14.79%, respectively (n = 5). For real sample analysis, three types of water samples (ground, surface, and tap water) were studied.

Highly porous nanostructured copper foam fiber impregnated with an organic solvent for headspace liquid-phase microextraction

A new headspace liquid-phase microextraction technique based on using a copper foam nanostructure substrate followed by gas chromatography-flame ionization detection was developed for the determination of volatile organic compounds in water and wastewater samples. The copper foam with highly porous nanostructured walls was fabricated on the surface of a copper wire by a rapid and facile electrochemical process and used as the extractant solvent holder. Propyl benzoate was immobilized in the pores of the copper foam coating and used for the microextraction of benzene, toluene, ethylbenzene and xylenes. The experimental parameters such as the type of organic solvent, desorption temperature, desorption time, salt concentration, sample temperature, equilibrium time and extraction time, were investigated and optimized. Under the optimum conditions, the method detection limit was between 0.06 and 0.25μgL−1. The relative standard deviation of the method for the analytes at 4–8μgL−1 concentration level ranged from 7.9 to 11%. The fiber-to-fiber reproducibility for three fibers prepared under the same condition was 9.3–12%. The enrichment factor was in the range of 615–744. Different water samples were analyzed for the evaluation of the method in real sample analysis. Relative recoveries for spiked tap, river and wastewater samples were in the range of 85–94%. Finally, the extraction efficiency of the method was compared with those of headspace single drop microextraction and headspace SPME with the commercial fibers.

High-sensitivity infrared attenuated total reflectance sensors for in situ multicomponent detection of volatile organic compounds in water.

In situ detection of volatile organic compounds (VOCs) in aqueous environments is imperative for ensuring the quality and safety of water supplies, yet it remains a challenging analytical task. We present a high-sensitivity method for in situ analysis of multicomponent VOCs at low concentrations based on the use of infrared attenuated total reflection (IR-ATR) spectroscopy. This protocol uses a unique ATR waveguide, which comprises a planar silver halide (AgCl(x)Br(1-x)) fiber with cylindrical extensions at both ends to increase the number of internal reflections, and a polymer coating that traps VOCs and excludes water molecules. Depending on the type of VOC and measurement scenario, IR spectra with specific frequency windows, scan times and spectral resolutions are obtained, from which concentration information is derived. This protocol allows simultaneous detection of multiple VOCs at concentrations around 10 p.p.b., and it enables accurate quantification via a single measurement within 5 min without the need for sample collection or sample pretreatment. This IR-ATR sensor technology will be useful for other applications; we have included a procedure for the analysis of protein conformation changes in Supplementary Methods as an example.

A fully automated portable gas chromatography system for sensitive and rapid quantification of volatile organic compounds in water

We present an automated portable GC system for the rapid and sensitive detection of VOCs in water.

Photocatalysis of Volatile Organic Compounds in water: Towards a deeper understanding of the role of cyclodextrins in the photodegradation of toluene over titanium dioxide

HypothesisCyclodextrin-assisted photodegradation of toluene was investigated in water in the presence of a photo-irradiated commercial titanium dioxide photocatalyst. It was expected that cyclodextrins could form water-soluble supramolecular host/guest complexes with the toluene and thus promote the approach of the pollutant on the TiO2 surface and enhance the phototocatalytic oxidation efficiency. ExperimentsPhotodegradation kinetics of toluene were investigated under UV-C and near-visible light radiation in aqueous suspensions of TiO2. Impact of cyclodextrin (CD) on the photocatalytic efficiency of TiO2 was evaluated with different cyclodextrins: α-CD, β-CD, γ-CD and RAME-β-CD. Host–guest association constants were determined by static headspace gas chromatography and affinity of cyclodextrins for the TiO2 surface by isothermal adsorption studies. Issue of the cyclodextrin stability during the degradation process was examined using Total Organic Carbon, NMR and MALDI-TOF analyses. FindingsToluene could be fully mineralized by TiO2 in water within hours, even if the presence of cyclodextrin caused a delay in the photodegradation process. The chemical nature of cyclodextrins was found to exert a significant influence on the extent of inhibitory effect, which was discussed in terms of balance between solubilization efficiency, substrate protection and coverage of active sites of TiO2 by competitive adsorption. The cyclodextrin degradation was also studied and discussed.

Determination of volatile organic compounds in water using headspace knotted hollow fiber microextraction

An efficient and effective headspace microextraction technique named static headspace knotted hollow fiber microextraction (HS-K-HFME) has been developed for the determination of volatile organic compounds (VOCs) in water samples. The knot-shaped hollow fiber is filled with 25μL of the extraction solvent. The excess solvent forms a large droplet (13μL) and is held in the center of the knot. Even after 20min of extraction time at high temperature (95°C) without cooling, there was still enough volume of extraction solvent for gas chromatography–mass spectrometry (GC–MS) analysis, which extends the choice of solvents for headspace LPME. Moreover, the knot-shaped fiber has a larger extraction contact interface, which increases the rate of mass transfer between the headspace and extraction solvent film attached to the fiber, thus improving the extraction efficiency. The effects of extraction solvent, temperature, stirring rate, salt concentration and extraction time on extraction performance were optimized. The calibration curves exhibited coefficients of determination (R2) ranging from 0.9957 to 0.9999 and the limit of detection (LOD) ranged from 0.2 to 10μgL−1. Relative standard deviations (RSDs) ranged from 4.5% to 11.6% for intraday measurements (n=5). Interday (n=15) values were between 2.2% and 12.9%. The relative recoveries (RRs) ranged from 90.3% to 106.0% for river water and 95.9% to 103.6% for wastewater.

Coupling of a headspace autosampler with a programmed temperature vaporizer for stable carbon and hydrogen isotope analysis of volatile organic compounds at microgram per liter concentrations.

One major challenge for the environmental application of compound-specific stable isotope analysis (CSIA) is the necessity of efficient sample treatment methods, allowing isolation of a sufficient mass of organic contaminants needed for accurate measurement of the isotope ratios. Here, we present a novel preconcentration technique--the coupling of a headspace (HS) autosampler with a programmed temperature vaporizer (PTV)--for carbon (δ(13)C) and hydrogen (δ(2)H) isotope analysis of volatile organic compounds in water at concentrations of tens of micrograms per liter. The technique permits large-volume injection of headspace samples, maintaining the principle of simple static HS extraction. We developed the method for multielement isotope analysis (δ(13)C and δ(2)H) of methyl tert-butyl ether (MTBE), benzene, toluene, ethylbenzene, and o-xylene (BTEX), and analysis of δ(13)C for chlorinated benzenes and ethenes. Extraction and injection conditions were optimized for maximum sensitivity and minimum isotope effects. Injection of up to 5 mL of headspace sample from a 20 mL vial containing 13 mL of aqueous solution and 5 g of NaCl (10 min of incubation at 90 °C) resulted in accurate δ(13)C and δ(2)H values. The method detection limits (MDLs) for δ(13)C were from 2 to 60 μg/L (MTBE, BTEX, chlorinated ethenes, and benzenes) and 60-97 μg/L for δ(2)H (MTBE and BTEX). Overall, the HS-PTV technique is faster, simpler, isotope effect-free, and requires fewer treatment steps and less sample volume than other extraction techniques used for CSIA. The environmental applicability was proved by the analysis of groundwater samples containing BTEX and chlorinated contaminants at microgram per liter concentrations.

Effective collection of volatile organic compounds in water using rimming flow with odorant-binding proteins

Effective collection of volatile organic compounds in water using rimming flow with odorant-binding proteins

Optimizations of packed sorbent and inlet temperature for large volume-direct aqueous injection-gas chromatography to determine high boiling volatile organic compounds in water

For the expanded application area, fast trace analysis of certain high boiling point (i.e., 150–250°C) volatile organic compounds (HVOCs) in water, a large volume-direct aqueous injection-gas chromatography (LV-DAI-GC) method was optimized for the following parameters: packed sorbent for sample on-line pretreatment, inlet temperature and detectors configuration. Using the composite packed sorbent self-prepared with lithium chloride and a type of diatomite, the method enabled safe injection of an approximately 50–100μL sample at an inlet temperature of 150°C in the splitless mode and separated HVOCs from water matrix in 2min. Coupled with a flame ionization detector (FID), an electron capture detector (ECD) and a flame photometric detector (FPD), the method could simultaneously quantify 27 HVOCs that belong to seven subclasses (i.e., halogenated aliphatic hydrocarbons, chlorobenzenes, nitrobenzenes, anilines, phenols, polycyclic aromatic hydrocarbons and organic sulfides) in 26min. Injecting a 50μL sample without any enrichment step, such as cryotrap focusing, the limits of quantification (LOQs) for the 27 HVOCs was 0.01–3μg/L. Replicate analyses of the 27 HVOCs spiked source and river water samples exhibited good precision (relative standard deviations≤11.3%) and accuracy (relative errors≤17.6%). The optimized LV-DAI-GC was robust and applicable for fast determination and automated continuous monitoring of HVOCs in surface water.

Temperature and air–water ratio influence on the air stripping of benzene, toluene and xylene

Volatile organic compounds in water and wastewater can be removed using air stripping. The effects of temperature and air-water ratios on the air stripping of benzene, toluene and xylene (BTX) from wastewater have been examined at a temperature range of 30–50°C and air-water ratios of 20–100. Removal efficiencies of >99%, >93% and 93% for BTX, respectively, were obtained at 50°C and air-water ratios of 100. The removal efficiencies increase non-linearly with temperature and air-water flow ratio. The effects of increasing temperature on the removal efficiency were found to be more significant at temperatures between 30 and 35°C than at 45 and 50°C. The effects of increasing water-air ratios on the removal efficiency were more significant at air-water ratios of 20–60 than at 80–100. The results indicate that a high removal of BTX can be achieved by operating the air stripper at high temperature conditions even at relatively low air-water ratios and vice versa.

A Porous Membrane Extraction and Microtrap System for On-line Monitoring of Volatile Organic Compounds in Water

based on the membrane pervaporation extraction and microtrap process, a sample pretreatment device for volatile organic compounds in water was constructed and evaluated systematically. the volatile organic compounds (vocs) in water samples could be extracted, preconcentrated, desorbed thermally, and then injected directly into gas chromatography automatically and continuously. two kinds of membrane materials, polydimethylsiloxane (pdms) and polyvinylidene fluoride (pvdf), extraction temperature, extraction time, and carrier gas flow rate were investigated with nine model compounds, chloroform, 1,2-dichloroethane, carbon tetrachloride, trichloroethylene, tetrachloroethylene, toluene, ethylbenzene, styrene, chlorobenzene. using this membrane extraction/microtrap device combined with gas chromatography and a flame ionization detector, under the conditions of 60 degrees c extraction temperature, 30 min concentration time and 8 ml/min carrier gas flow, the detection limits of chlorinated hydrocarbons were in the range of 0. 003-0. 041 mu g/l. the rsds between 2. 7% and 13. 0% were obtained. coefficients of correlation were all above 0. 9936. this result demonstrated that this device was very useful for monitoring volatile organic compounds in water.

A Porous Membrane Extraction and Microtrap System for On-line Monitoring of Volatile Organic Compounds in Water

Based on the membrane pervaporation extraction and microtrap process,a sample pretreatment device for volatile organic compounds in water was constructed and evaluated systematically.The volatile organic compounds(VOCs) in water samples could be extracted,preconcentrated,desorbed thermally,and then injected directly into gas chromatography automatically and continuously.Two kinds of membrane materials,polydimethylsiloxane(PDMS) and polyvinylidene fluoride(PVDF),extraction temperature,extraction time,and carrier gas flow rate were investigated with nine model compounds,chloroform,1,2-dichloroethane,carbon tetrachloride,trichloroethylene,tetrachloroethylene,toluene,ethylbenzene,styrene,chlorobenzene.Using this membrane extraction/microtrap device combined with gas chromatography and a flame ionization detector,under the conditions of 60 ℃ extraction temperature,30 min concentration time and 8 mL/min carrier gas flow,the detection limits of chlorinated hydrocarbons were in the range of 0.003-0.041 μg/L.The RSDs between 2.7% and 13.0% were obtained.Coefficients of correlation were all above 0.9936.This result demonstrated that this device was very useful for monitoring volatile organic compounds in water.

Effective Collecting Method of Volatile Organic Compounds in Water by Bubbling

Effective Collecting Method of Volatile Organic Compounds in Water by Bubbling