Quantification Of Volatile Organic Compounds Research Articles

MONITORING AND TREATMENT OF VOLATILE ORGANIC COMPOUNDS IN DRINKING WATER COMPARATIVE STUDY

Volatile organic compounds (VOCs) present in drinking water, have a negative impact on human health and environment especially that formed during chlorination step in the treatment process, they classified as possible human carcinogens, when exceed the permissible limits. The identification and quantification of VOCs performed by purge & trap GC/MS instrument, using reference analytical method (EPA 524.2, 1995). A monthly monitoring comparative study established during 2016 in both input and output of Shubra El-Kheima (Water Treatment Plants WTP) (1 km far from Nile River on Al-Sharqawia canal at the northern border of capital Cairo) and South Alamein WTP (270 km downstream far from the Nile River on Alhamam canal at North Coast of Egypt). The study investigated and recorded the presence of disinfection by-product of Volatile Organic Compounds (DBPs-VOCs) (CHCl3, CHCl2Br, CHClBr2 and CHBr3) which exceeded the permissible limits in the produced Water of South Alamein WTP and its boosters. The study succeeded in estimating the amount of granular activated carbon GAC required to reduce (DBPs-VOCs) values from (178 µg/l) to (94 µg/l) in the produced water of South Alamein WTP, The duration frequency for changing (GAC)would be approximately (581 ton)/(17 days).

Identification and quantification of VOCs by proton transfer reaction time of flight mass spectrometry: An experimental workflow for the optimization of specificity, sensitivity, and accuracy.

Proton transfer reaction time of flight mass spectrometry (PTR‐ToF‐MS) is a direct injection MS technique, allowing for the sensitive and real‐time detection, identification, and quantification of volatile organic compounds. When aiming to employ PTR‐ToF‐MS for targeted volatile organic compound analysis, some methodological questions must be addressed, such as the need to correctly identify product ions, or evaluating the quantitation accuracy. This work proposes a workflow for PTR‐ToF‐MS method development, addressing the main issues affecting the reliable identification and quantification of target compounds. We determined the fragmentation patterns of 13 selected compounds (aldehydes, fatty acids, phenols). Experiments were conducted under breath‐relevant conditions (100% humid air), and within an extended range of reduced electric field values (E/N = 48–144 Td), obtained by changing drift tube voltage. Reactivity was inspected using H3O+, NO+, and O2 + as primary ions. The results show that a relatively low (<90 Td) E/N often permits to reduce fragmentation enhancing sensitivity and identification capabilities, particularly in the case of aldehydes using NO+, where a 4‐fold increase in sensitivity is obtained by means of drift voltage reduction. We developed a novel calibration methodology, relying on diffusion tubes used as gravimetric standards. For each of the tested compounds, it was possible to define suitable conditions whereby experimental error, defined as difference between gravimetric measurements and calculated concentrations, was 8% or lower.

Quantification of naphthalene in soil using solid-phase microextraction, gas-chromatography with mass-spectrometric detection and standard addition method

Development of simple, fast and accurate methods for quantification of volatile organic compounds (VOCs) in soil samples is important for providing greater efficiency of analytical laboratories in Kazakhstan and other developing countries. Naphthalene is a model polycyclic aromatic hydrocarbon (PAH), belonging to a group of compounds of significant concern due to environmental impact. Solid-phase microextraction (SPME) is an optimal method for solvent-free automated sample preparation for determination of VOCs in environmental samples. In this work, the method for quantification of naphthalene in soil based on headspace SPME, gas chromatography with mass spectrometric detection, and standard addition calibration was developed. The parameters of SPME and sample equilibration after spiking with standards were optimized for better control of the soil matrix effect. The SPME temperature 80 °C provided the greatest accuracy of naphthalene responses for soils with different matrix and humidity. Equilibration of soil samples after spiking with standards for 6 h at 80 °C provided stabilization of responses in soils with different matrix and water content. The greatest accuracy and precision were achieved after equilibration of the samples for 8 h. The method provides recoveries of 105-119% in the concentration range 0.01-0.1 ng g-1 with detection limit 0.001 ng g-1. The developed method was applied for quantification of naphthalene in real soil samples collected in Almaty, Kazakhstan. The measured concentration of naphthalene in real soil samples varied in the range of 1.4 to 47 ng g-1. In five out of ten collected soil samples concentration exceeded a maximum permissible concentration of 15 ng g-1.

Near infrared chemo-responsive dye intermediaries spectra-based in-situ quantification of volatile organic compounds

Volatile organic compounds (VOCs) detection and measurement in materials with near infrared spectroscopy (NIRS) have been an unresolved constraint till date. This paper focused on the use of NIRS for rapid detection and quantification of pure VOCs (ethanol, ethyl acetate and acetic acid) in mixed VOCs via employing sensitive intermediary chemo-responsive dyes as capture probes, whose NIRS spectra were scanned, preprocessed and used to build partial least squares (PLS) prediction models. Average predicted rates based on the PLS-built prediction models for the pure VOCs in the mixed VOCs yielded 98.60±17.41%. 78.26% of the pure VOCs prediction rates ranged between 85 and 114% and normally distributed. The high prediction rates achieved imply the technique may be deployed as a panacea to widen the usage scope of NIRS and e-nose based colorimetric sensors for rapid detection and quantification of VOCs content in materials which hitherto had been a constraint for both systems.

Evaluation of peroxidative stress of cancer cells in vitro by real-time quantification of volatile aldehydes in culture headspace.

Peroxidation of lipids in cellular membranes results in the release of volatile organic compounds (VOCs), including saturated aldehydes. The real-time quantification of trace VOCs produced by cancer cells during peroxidative stress presents a new challenge to non-invasive clinical diagnostics, which as described here, we have met with some success. A combination of selected ion flow tube mass spectrometry (SIFT-MS), a technique that allows rapid, reliable quantification of VOCs in humid air and liquid headspace, and electrochemistry to generate reactive oxygen species (ROS) in vitro has been used. Thus, VOCs present in the headspace of CALU-1 cancer cell line cultures exposed to ROS have been monitored and quantified in real time using SIFT-MS. The CALU-1 lung cancer cells were cultured in 3D collagen to mimic in vivo tissue. Real-time SIFT-MS analyses focused on the volatile aldehydes: propanal, butanal, pentanal, hexanal, heptanal and malondialdehyde (propanedial), that are expected to be products of cellular membrane peroxidation. All six aldehydes were identified in the culture headspace, each reaching peak concentrations during the time of exposure to ROS and eventually reducing as the reactants were depleted in the culture. Pentanal and hexanal were the most abundant, reaching concentrations of a few hundred parts-per-billion by volume, ppbv, in the culture headspace. The results of these experiments demonstrate that peroxidation of cancer cells in vitro can be monitored and evaluated by direct real-time analysis of the volatile aldehydes produced. The combination of adopted methodology potentially has value for the study of other types of VOCs that may be produced by cellular damage.

Quantitative determination of volatile organic compounds formed during Polylactide processing by MHS-SPME

Polylactide (PLA), a bio-based polyester, has been used in wide applications including food packaging. Nevertheless, it is well known that mass transfer occurs between packaging polymer and foodstuff leading to safety and quality issues. In this sense, volatile organic compounds (VOCs) present in packaging materials can migrate to the food in contact, changing its sensorial properties. Up to date, no study has focused on quantification of VOCs in PLA during its processing, which needs an optimized methodology to measure compounds at very low concentrations. In this study, different PLA samples in form of pellets, extruded films and thermoformed samples were studied in order to determine the VOCs present in each step of processing and to quantify them using headspace extraction methodology (MHS-SPME). Several volatile organic compounds were determined such as aldehydes, ethanol, acetone, acetic acid and lactides. Among the VOCs identified, three compounds were quantified: acetaldehyde; 2-methyl-2-propanol; 2,3-pentanedione. Acetaldehyde and 2,3-pentanedione increased after the extrusion and then decreased or disappeared after thermoforming. The results showed that residual acetaldehyde in PLA could be an important marker for the industry in the selection of PLA grades.

Chemical composition of volatile compounds in two red seaweeds, Pterocladiella capillacea and Osmundaria obtusiloba, using static headspace gas chromatography mass spectrometry

Volatile organic compounds (VOCs) from the red seaweeds Pterocladiella capillacea and Osmundaria obtusiloba were obtained by static headspace extraction and then analyzed qualitatively by gas chromatography mass spectrometry (GC-MS) and quantitatively by gas chromatography (GC) equipped with a flame ionization detector (FID). In total, 31 constituents were identified in the two species of algae. In P. capillacea, among the 21 constituents (100%), the major ones were hexanal (50.4%), 2-pentylfuran (9.2%), and heptadecene (8.8%). In O. obtusiloba, of the 21 constituents (100%), the most representatives were heptadecene (57.3%), hexanal (20.5%), and 1-pentadecene (2.6%). This is the first report on the identification and quantification of VOCs in the Rhodophyta, P. capillacea and O. obtusiloba.

Determination of volatile organic compounds in air by portable gas chromatography-mass spectroscopy

Objective: To investigate the method of portable gas chromatography-mass spectroscopy (GC-MS) for the determination of common volatile organic compounds in air. Methods: The static volumetric method was used, with highly purified nitrogen gas as the diluents gas, to prepare the mixed standard gas of common volatile organic compounds with various mass concentrations. A portable GC-MS handheld probe was used for sampling and measurement, retention time and characteristic ion were used for qualitative analysis, and the full-scan mode was used for quantitative analysis. Results: The correlation coefficient of 12 volatile organic compounds determined by this method was higher than 0.999. The minimum detection mass concentration was 0.02~0.12 mg/m3, and the minimum quantitative mass concentration was 0.07~0.40 mg/m3. The relative standard deviation of precision was 4.10%~12.50%; the relative deviation of acetone, benzene, methylbenzene, and dimethylbenzene was-13.56% , 9.03% , -10.82% , and 8.67% , respectively. Conclusion: Portable GC-MS method can be used for the qualitative analysis and quantification of volatile organic compounds in occupational hazard factors and provide technical supports for identification of occupational hazard factors.

Hazardous aromatic VOC quantification through spectroscopic analysis and intelligent modeling to assess drinking water quality

Concentrations within the micromole range have been accurately determined for mixtures of two common aromatic volatile organic compounds (VOCs) that are hazardous for both the environment and human health: styrene and 1,2,4-trimethylbenzene. This task has been developed by combining 165 UV/Vis absorption measurements and intelligent modeling based on artificial neural networks (ANNs), and is especially relevant as these compounds have been located in sources of drinking water within the concentration range covered. The performance of the designed non-linear models proves the existence of a relation between spectroscopic information and compound concentration, as well as the ability to obtain reliable quantifying chemometric tools for environmental control applications. The average mean absolute errors for three internal validations were near 0.5μM and 1.5μM for styrene and 1,2,4-trimethylbenzene concentration estimation, respectively.

A Wearable MEMS Gas Chromatograph for Multi-Vapor Determinations

A wearable gas chromatographic microanalytical system (μGC) for near-real-time recognition and quantification of volatile organic compounds (VOC) in complex mixtures encountered in working environments is described. The battery powered μGC prototype measures 20×15×9 cm, weighs just 2.1 kg, has 3-D printed packaging, and can be worn on the belt to autonomously measure exposures to industrial VOC mixtures several times per hour. Novel features of the discrete DRIE-Si/Pyrex micro-component chips include a dual-adsorbent μpreconcentrator/focuser (μPCF) with split-flow injections as narrow as 600 ms (benzene), a 6-m long segmented separation μcolumn with zone heating for power efficient separations; and a fluidically redesigned array of μchemiresistors (μCR) with thiolate-monolayer protected Au nanoparticle (MPN) interface films that provide sensitive detection and diverse response patterns for recognizing eluting VOCs. Embedded microcontrol allows for continuous unattended operation and storage of data for post-exposure downloading and analysis. In our first tests of the complete prototype, we have demonstrated reproducible analyses of mixtures of up to 9 VOCs in 2.5 min (sampling and analysis), linear calibration curves, unique response patterns for mixture components, sub-ppm LODs, and stable responses for 5 days. Initial mock field tests demonstrated successful monitoring of rapidly changing concentrations of three VOCs during a solvent handling task.

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.

Breath testing as potential colorectal cancer screening tool.

Although colorectal cancer (CRC) screening is included in organized programs of many countries worldwide, there is still a place for better screening tools. In this study, 418 breath samples were collected from 65 patients with CRC, 22 with advanced or nonadvanced adenomas, and 122 control cases. All patients, including the controls, had undergone colonoscopy. The samples were analysed with two different techniques. The first technique relied on gas chromatography coupled with mass spectrometry (GC-MS) for identification and quantification of volatile organic compounds (VOCs). The T-test was used to identify significant VOCs (p values < 0.017). The second technique relied on sensor analysis with a pattern recognition method for building a breath pattern to identify different groups. Blind analysis or leave-one-out cross validation was conducted for validation. The GC-MS analysis revealed four significant VOCs that identified the tested groups; these were acetone and ethyl acetate (higher in CRC), ethanol and 4-methyl octane (lower in CRC). The sensor-analysis distinguished CRC from the control group with 85% sensitivity, 94% specificity and 91% accuracy. The performance of the sensors in identifying the advanced adenoma group from the non-advanced adenomas was 88% sensitivity, 100% specificity, and 94% accuracy. The performance of the sensors in identifying the advanced adenoma group was distinguished from the control group was 100% sensitivity, 88% specificity, and 94% accuracy. For summary, volatile marker testing by using sensor analysis is a promising noninvasive approach for CRC screening.

Electronic Nose for Recognition of Volatile Vapor Mixtures Using a Nanopore-Enhanced Opto-Calorimetric Spectroscopy.

An electronic nose (e-nose) for identification and quantification of volatile organic compounds (VOCs) vapor mixtures was developed using nanopore-enhanced opto-calorimetric spectroscopy. Opto-calorimetric spectroscopy based on specific molecular vibrational transitions in the mid infrared (IR) "molecular fingerprint" regime allows highly selective detection of VOCs vapor mixtures. Nanoporous anodic aluminum oxide (AAO) microcantilevers, fabricated using a two-step anodization and simple photolithography process, were utilized as highly sensitive thermomechanical sensors for opto-calorimetric signal transduction. The AAO microcantilevers were optimized by fine-tuning AAO nanopore diameter in order to enhance their thermomechanical sensitivity as well as their surface area. The thermomechanical sensitivity of a bilayer AAO microcantilever with a 60 nm pore diameter was approximately 1 μm/K, which is far superior to that of a bilayer plain silicon (Si) microcantilever. The adsorbed molecules of VOCs mixtures on the AAO microcantilever were fully recognized and quantified by variations of peak positions and amplitudes in the opto-calorimetric IR spectra as well as by shifts in the resonance frequency of the AAO microcantilever with the adsorbed molecules. Furthermore, identification of complex organic compounds with a real industrial sample was demonstrated by this e-nose system.

A method for quantification of volatile organic compounds in blood by SPME-GC-MS/MS with broader application: From non-occupational exposure population to exposure studies.

Humans are continuously exposed to volatile organic compounds (VOCs) as these chemicals are ubiquitously present in most indoor and outdoor environments. In order to assess recent exposure to VOCs for population-based studies, VOCs are measured in the blood of participants. This work describes an improved method to detect 12 VOCs by head-space solid-phase microextraction gas chromatography coupled with isotope-dilution mass spectrometry in selected reaction monitoring mode (SPME-GC-MS/MS). This method was applied to the analysis of trihalomethanes, styrene, trichloroethylene, tetrachloroethylene and BTEX (benzene, toluene, ethylbenzene, m-xylene, p-xylene, o-xylene) in a population-based biomonitoring study (Canadian Health Measures Survey). The method showed good linearity (>0.990) in the range of 0.010-10μg/L and detection limits between 0.007 and 0.027μg/L, precision better than 25% and good accuracy (±25%) based on proficiency testing materials. Quality Control data among runs over a 7 month period showed %RSD between 14 and 25% at low levels (∼0.03μg/L) and between 9 and 23% at high levels (∼0.4μg/L). The method was modified to analyze samples from a pharmacokinetic study in which 5 healthy volunteers were exposed to single, binary and quaternary mixtures of CTEX (chloroform, ethylbenzene, toluene and m-xylene), thus the expected concentration in blood was 1 order of magnitude higher than those found in the general population. The method was modified by reducing the sample size (from 3g to 0.5g) and increasing the upper limit of the concentration range to 395μg/L. Good linearity was found in the range of 0.13-395μg/L for toluene and ethylbenzene and 0.20-609μg/L for m/p-xylene. Quality control data among runs over the period of the study (n=13) were found to vary between 7 and 25%.

Effect of Water Vapor Content and Gas Composition on Quantification of Volatile Organic Compounds from Wild Rocket by SPME

A quantification method based on solid-phase microextraction (SPME) and external standard calibration for analysis of volatile organic compounds (VOCs) emitted from fresh produce in a dynamic environment, such as during storage in modified atmosphere (MA) packages, was investigated in this study. The effects of the water vapor content, temperature, and gas matrix composition on the extraction efficiencies of dimethyl sulfide, nitromethane, 3-methylfuran, dimethyl disulfide, and ethyl 3-methylbutyrate were investigated on an 85-μm carboxen/polydimethylsiloxane fiber. At VOC concentrations of 15.7 to 32.7 ng L−1, the water vapor content and temperature had negative effects on the extraction efficiency of dimethyl sulfide and nitromethane. At high CO2 concentrations (20–50 % CO2 balanced with N2), the extraction efficiency for all of the investigated VOCs decreased. However, the VOC concentrations determined from a 10 % O2 and 10 % CO2 matrix were the same as those measured in 20 % O2 and 0 % CO2 or 0 % O2 and 20 % CO2 matrices. For quantification of VOCs emitted from wild rocket stored under dynamic gas concentrations, a gas matrix composed of 10 % O2 and 10 % CO2 with a relative humidity above 85 % can be used for external standard calibration by maintaining the same temperature during the extraction of VOCs from the samples, as well as during the calibration.

Proton transfer reaction-mass spectrometry: online and rapid determination of volatile organic compounds of microbial origin.

Analytical tools for the identification and quantification of volatile organic compounds (VOCs) produced by microbial cultures have countless applications in an industrial and research context which are still not fully exploited. The various techniques for VOC analysis generally arise from the application of different scientific and technological philosophies, favoring either sample throughput or chemical information. Proton transfer reaction-mass spectrometry (PTR-MS) represents a valid compromise between the two aforementioned approaches, providing rapid and direct measurements along with highly informative analytical output. The present paper reviews the main applications of PTR-MS in the microbiological field, comprising food, environmental, and medical applications.

Discrimination and quantification of volatile organic compounds in the ppb-range with gas sensitive SiC-FETs using multivariate statistics

Gas sensitive field effect transistors based on silicon carbide, SiC-FETs, have been studied for indoor air quality applications. The selectivity of the sensors was increased by temperature cycled operation, TCO, and data evaluation based on multivariate statistics. Discrimination of benzene, naphthalene, and formaldehyde independent of the level of background humidity is possible by using shape describing features as input for Linear Discriminant Analysis, LDA, or Partial Least Squares – Discriminant Analysis, PLS-DA. Leave-one-out cross-validation leads to a correct classification rate of 90% for LDA, and for PLS-DA a classification rate of 83% is achieved. Quantification of naphthalene in the relevant concentration range, i.e., 0–40ppb, was performed by Partial Least Squares Regression and a combination of LDA with a second order polynomial fit function. The resolution of the model based on a calibration with three concentrations was approximately 8ppb at 40ppb naphthalene for both algorithms.Hence, the suggested strategy is suitable for on demand ventilation control in indoor air quality application systems.

P36: Évaluation of fetal exposure to environmental pollutants by quantification of volatile organic compounds, pesticides and associated metabolites in meconium

Introduction Meconium is the earliest stools of newborn. It starts forming from the 13th week of gestation in intestinal contents and accumulates until birth. Usually, it is expelled by the newborn between 24 and 48 hours after birth. The analysis of this complex matrix allows the determination of fetal exposure to xenobiotics over the last six months of pregnancy. The objective of the project “PENEW” (Environment Pregnancy and NEWborn malformations, PHRC 2010 CHU Rennes) is to determine a correlation between the occurrence of malformations and fetal exposure. Analytical developments for the determination in meconium of VOCs (Volatile Organic Compounds) including BTEX (benzene, toluene, ethylbenzene, xylenes) and two chlorinated solvents (trichloroethylene and tetrachloroethylene), BTEX metabolites, pesticides (pyrethroids, organophosphates...) and associated metabolites (dialkylphosphates...) have been performed. These analytical methods were applied to over two hundred meconium samples. Methods Sample preparation of meconium is very complex due to the specific physico-chemical properties of the matrix. VOCs were measured with very low quantification limits (80 pg g-(1)) by Head- Space Solid Phase MicroExtraction (HS-SPME) with GC/MS (Gas Chromatography coupled to Mass Spectrometry). The same sample could then be re-used for the analysis of non volatile compounds. A multi-residue method was therefore applied for the quantification of pesticides, metabolites of pesticides and metabolites of VOCs. The sample preparation was composed by two liquid-liquid extractions followed by two successive purifications by SPE (Solid Phase Extraction). The analyses were carried out by LC/MS/MS (Liquid Chromatography with Tandem Mass Spectrometry). Three different LC columns were used: an ion exchange column for the glyphosate analysis; a HILIC column for the analysis of four dialkylphosphates and a reversed-phase column for all the other target compounds. The quantification limits of this multi-residue method were in average of 29 ng g -1 . Results All VOCs were determined in meconium samples. The highest concentrations were obtained for benzene and toluene. These two compounds and trichloroethylene were measured in each meconium sample. Tetrachloroethylene, ethylbenzene and xylenes were quantified in few samples. Several metabolites (ocresol, hippuric acid, muconic acid, PGA and S-BMA) were determined in most samples. Several pesticides (dichlorvos, propoxur, malathion, cypermethrine and some metabolites of pesticides: dialkylphosphates) were also occasionally quantified. Conclusion These two analytical methods based on the use of the same meconium sample enabled the quantification of 33 target molecules. Most of the investigated compounds were determined in the meconium samples. In a further step, a relationship between these results on pollutant exposure and the occurrence of fetal malformations will be studied.

Quantification of volatile organic compounds in smoke from prescribed burning and comparison with occupational exposure limits

Abstract. Prescribed burning represents a serious threat to personnel fighting fires due to smoke inhalation. The aim of this study was to investigate exposure by foresters to smoke from prescribed burning, focusing on exposure to volatile organic compounds (VOCs). The methodology for smoke sampling was first evaluated. Potentially dangerous compounds were identified among the VOCs emitted by smoke fires at four prescribed burning plots located around Corsica. The measured mass concentrations for several toxic VOCs were generally higher than those measured in previous studies due to the experimental framework (short sampling distance between the foresters and the flame, low combustion, wet vegetation). In particular, benzene, phenol and furfural exceeded the legal short-term exposure limits published in Europe and/or the United States. Other VOCs such as toluene, ethybenzene or styrene remained below the exposure limits. In conclusion, clear and necessary recommendations were made for protection of personnel involved in fighting fires.

Discrimination and Quantification of Volatile Organic Compounds in the ppb-Range with Gas Sensitive SiC-Field Effect Transistors

Gas sensitive FETs based on SiC have been studied for the discrimination and quantification of hazardous volatile organic compounds (VOCs) in the low ppb range. The sensor performance was increased by temperature cycled operation (TCO) and data evaluation based on multivariate statistics, here Linear Discriminant Analysis (LDA). Discrimination of formaldehyde, naphthalene and benzene with varying concentrations in the ppb range is demonstrated. In addition, it is shown that naphthalene can be quantified in the relevant concentration range independent of the relative humidity and against a high ethanol background. Hence, gas sensitive SiC-FETs are suitable sensors for determining indoor air quality.