Online sequential analysis of volatile and semivolatile organic compounds in water matrices by double robotic sample preparations and dual-channel mono and comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry system

Background Following creation of an IPAA in patients with ulcerative colitis (UC), more than 60% of subjects develop inflammatory complications. The current objective assessment for inflammation of the pouch is limited to surrogate stool and blood biomarkers or endoscopy. The development of non-invasive and accurate biomarkers for the assessment of IPAA inflammation is an area of unmet need. Measurement of exhaled breath volatile organic metabolome compounds (VOCs) has shown promise as a biomarker for the diagnosis and monitoring of inflammatory disorders. We here aimed to characterize the pattern of VOCs in the exhaled breath of patients with an IPAA and assess whether VOC analysis is able to discriminate patients with endoscopically active IPAA inflammation from patients without IPAA inflammation. Methods This is a cross-sectional study of patients with an IPAA created for the management of UC. Exhaled breath samples were collected at time of endoscopic evaluation of the pouch and 97 VOC metabolites assessed via selective ion flow tube mass spectrometry (SIFT-MS). The IPAA cohort was dichotomized using the endoscopic pouch disease activity index (PDAI) into endoscopic PDAI of >= 4 (severe inflammation), or endoscopic PDAI score <= 1 (mild or no inflammation). Principle component analysis (PCA) was conducted to reveal the VOCs with the strongest discriminatory capability and principle component regression (PCR) was performed to assess the association of exhaled breath VOC analysis in differentiating the groups. Results Exhaled breath metabolome analysis was performed on 10 subjects with PDAI >=4 and 7 subjects with PDAI <=1. Demographics are provided in Table 1. PCA indicated robust discrimination of the two groups based on breath VOCs (Figure 1). 10 out of 97 VOCs were up-regulated in the PDAI >=4 group compared to control, including ammonia and hydrogen sulfide. Isopropenyltoluene, tetrachloroethylene, and 3-pentanone provided the highest contribution to differentiate between the cohorts (Figure 2). Receiver operative curve (ROC) analysis of the PCR model indicated an area under the curve (AUC) of 0.81 (0.61-99), suggesting a strong association of breath VOCs with inflammation of the pouch (Figure 1). Conclusion VOC exhaled breath metabolome analysis shows a strong ability to discriminate patients with severe endoscopic pouch inflammation from patients with minimal to no endoscopic inflammation. The differences in reported VOCs point toward metabolic differences in bacterial fermentation, lipid and carbohydrate metabolism, and an increase in reactive oxygen species in patients with endoscopic pouch inflammation. Validation studies addressing the role of VOC analysis for non-invasive disease assessment patients with IPAA are ongoing.

A new method, purge-and-membrane mass spectrometry (PAM MS), is introduced for the analysis of volatile organic compounds (VOCs) in water and soil samples. In this method, VOCs are purged from water or soil samples with an inert gas and the stream is directed through a sheet membrane module. The VOCs pervaporate through the membrane directly into the ion source of a mass spectrometer. The limits of detection for nonpolar VOCs such as halogenated hydrocarbons, benzene, toluene, and xylenes were below micrograms per liter in water samples and at low micrograms per kilogram levels in soil samples. The correlation coefficients measured for the compounds studied were typically better than 0.9999 and 0.9975 in water and soil samples, respectively. The relative standard deviations were between 0.5 and 2.0% with water samples and between 4.8 and 14.0% with soil samples. These results demonstrate excellent linearity and repeatability. PAM MS thus provides a highly sensitive, selective, accurate, solvent-free, and rapid analytical method. Tens of samples can be analyzed reliably within 1 h.

Sample preparation for the analysis of volatile organic compounds in air and water matrices

BackgroundComprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF MS) has been proposed as a powerful new tool for multidimensional analysis of complex chemical mixtures. We investigated GCxGC-TOF MS as a new method for identifying volatile organic compounds (VOCs) in normal human breath.MethodsSamples of alveolar breath VOCs and ambient room air VOC were collected with a breath collection apparatus (BCA) onto separate sorbent traps from 34 normal healthy volunteers (mean age = 40 yr, SD = 17 yr, male/female = 19/15). VOCs were separated on two serial capillary columns separated by a cryogenic modulator, and detected with TOF MS. The first and second dimension columns were non-polar and polar respectively.ResultsBCA collection combined with GC×GC-TOF MS analysis identified approximately 2000 different VOCs in samples of human breath, many of which have not been previously reported. The 50 VOCs with the highest alveolar gradients (abundance in breath minus abundance in ambient room air) mostly comprised benzene derivatives, acetone, methylated derivatives of alkanes, and isoprene.ConclusionsCollection and analysis of breath VOCs with the BCA-GC×GC-TOF MS system extended the size of the detectable human volatile metabolome, the volatome, by an order of magnitude compared to previous reports employing one-dimensional GC-MS. The size of the human volatome has been under-estimated in the past due to coelution of VOCs in one-dimensional GC analytical systems.

A new method for the simultaneous determination of 12 volatile organic compounds (trans-1,2-dichloroethene, 1,1,1-trichloroethane, benzene, 1,2-dichloroethane, trichloroethene, toluene, 1,1,2-trichloroethane, tetrachloroethene, ethylbenzene, m-, p-, o-xylene) in water samples by headspace solid phase microextraction (HS–SPME)–gas chromatography mass spectrometry (GC–MS) was described, using a 100 µm PDMS (polydimethylsiloxane) coated fibre. The response surface methodology was used to optimise the effect of the extraction time and temperature, as well as the influence of the salt addition in the extraction process. Optimal conditions were extraction time and temperature of 30 min and −20°C, respectively, and NaCl concentration of 4 mol L−1. The detection limits were in the range of 1.1 × 10−3–2.3 µg L−1 for the 12 volatile organic compounds (VOCs). Global uncertainties were in the range of 4–68%, when concentrations decrease from 250 µg L−1 down to the limits of quantification. The method proved adequate to detect VOCs in six river samples.

半挥发性有机物主要包括多环芳烃类(PAHs)、邻苯二甲酸酯类(PAEs)、有机氯农药类(OCPs)和硝基苯类(NBs)等化合物,这些物质多具有致癌、致畸、致突变作用,以及内分泌干扰效应。因此,快速准确测定水中半挥发性有机物非常重要,目前国内尚无水中半挥发性有机物的检测标准。该研究从氮吹温度、水样pH值和萃取时间3个方面进行了优化,旨在建立一种液液萃取-气相色谱-质谱(LLE-GC-MS)同时测定水中46种半挥发性有机物的方法。结果表明:氮吹温度对46种半挥发性有机物的回收率影响不大,考虑回收率及浓缩效率,将氮吹温度设定为35 ℃;水样在中性环境下萃取效果好于碱性环境下的效果;萃取时间由7 min增加至10 min时,回收率也随之提高,但时间增加至15 min时,17种(占比37%)化合物回收率有所增加,29种(占比63%)化合物回收率则呈降低趋势。因此,将萃取时间设定为每次10 min。采用气相色谱-质谱仪进行检测,内标法定量。该方法在20.0~2000 μg/L范围内线性良好,相关系数(r 2)≥0.9916, 46种SVOCs检出限为0.28~16.55 ng/L,定量限为0.92~55.16 ng/L;在0.02、0.2、0.4 μg/L 3个加标水平下的平均回收率为63.6%~125%,相对标准偏差(n=6)为1.03%~17.0%。采用该方法检测了黄河流域济南段的27个地表水样品,检出的物质以PAEs和PAHs为主,2种OCPs在部分点位有检出,NBs均未检出。该方法操作简单,通用性强,准确度及精密度良好,检出限低,适用于地表水及地下水中46种半挥发性有机物的同时检测。

Increasing interest is noticed in the potential of volatile organic compound (VOC) analysis as non-invasive diagnostic biomarker in clinical medical practice. The spectrum of VOCs, originating from (patho)physiological metabolic processes in the human body and detectable in bodily excrements, such as exhaled breath, urine and feces, harbors a magnificent source of information. Thus far, the majority of studies have focused on VOC analysis in exhaled breath, aiming at identification of disease-specific VOC profiles. Recently, an increasing number of studies have evaluated the usability of VOC present in the headspace of feces in the diagnostic work-up of a wide range of gastrointestinal diseases. Promising results have been demonstrated particularly in those diseases in which microbiota alterations are considered to play a significant etiological role, such as colorectal carcinoma, inflammatory bowel disease, irritable bowel syndrome, celiac disease and infectious bowel diseases. In addition, fecal VOC analysis seems to have potential as a diagnostic biomarker for extra-intestinal diseases, including bronchopulmonary dysplasia and sepsis. Different methods for VOC analysis have been used in medical studies, such as gas-chromatography mass spectrometry, selected-ion flow tube-mass spectrometry, ion-mobility spectrometry, and electronic nose devices. In this review, the available literature on the potential of fecal VOCs as diagnostic biomarker, including an overview of relevant VOC detection techniques, is discussed. In addition, future hurdles, which need to be taken prior to implementation of VOC analysis in daily clinical practice, are outlined.

Various techniques have been employed in the analysis of volatile organic compounds (VOCs). However, these techniques are insufficient for the precise analysis of tobacco smoke VOCs because of the complexity of the operating system, system instability, or poor sensitivity. To overcome these problems, a combined system of VOC preconcentrator, gas chromatograph, and olfactometer has been developed. The performance of this new system was evaluated in the analysis of VOCs in tobacco smoke and applied to the odor profiling of sidestream smoke (SSS) that has not been sufficiently investigated in the past. A VOC sample in a gas-sampling bag was injected into a gas chromatograph through a preconcentrator, where it was concentrated, dehydrated, and cryo-focused. Separated VOCs were introduced into a mass spectrometer (for qualitative and quantitative analysis) and a sniffing port (for odor profiling) by a splitting device. In addition to the conventional Gas Chromatography-Olfactometry (GC-O) technique that was used for describing the odor quality of each compound, the odor intensity was estimated based on the dilution ratio of the sample, Aroma Direct Dilution Analysis (ADDA). Also, the contribution of each VOC to the overall SSS odor was estimated by sensory evaluation. This system permitted adequate characterization of the VOCs. The reproducibility of quantification was also good enough with Coefficient of Variation (CV) values less than about 5% (n = 5). With the GC-O technique, we obtained an SSS odor profile composed of over 30 odorants. ADDA indicated that seven odorants were sufficient to characterize SSS odor. In addition, the omit-test revealed that three odor attributes, (‘metallic’, ‘potato-like’, and ‘popcorn-like’) were most important for the characterization of SSS odor.

Many studies have been conducted since 1970 to characterize concentrations of semivolatile organic compounds (SVOCs) in highway runoff and urban stormwater. To a lesser extent, studies also have characterized concentrations of volatile organic compounds (VOCs), estimated loads of SVOCs, and assessed potential impacts of these contaminants on receiving streams. This review evaluates the quality of existing data on SVOCs and VOCs in highway runoff and urban storm water and summarizes significant findings. Studies related to highways are emphasized when possible. The review included 44 articles and reports that focused primarily on SVOCs and VOCs. Only 17 of these publications are related to highways, and 5 of these 17 are themselves review papers. SVOCs in urban stormwater and sediments during the late 1970's to mid-1980's were the subject of most studies. Criteria used to evaluate data quality included documentation of sampling protocols, analytical methods, minimum reporting limit (MRL) or method detection limit (MDL), quality-assurance protocols, and quality-control samples. The largest deficiency in documenting data quality was that only 10 percent of the studies described where water samples were collected in the stream cross section. About 80 percent of SVOCs in runoff are in the suspended solids. Because suspended solids can vary significantly even in narrow channels, concentrations from discrete point samples and contaminant loads estimated from those samples are questionable without information on sample location, or use of field quality-control samples. Comparing results of different studies and evaluating the quality of environmental data, especially for samples with low concentrations, is difficult without this information. The most significant factor affecting SVOC concentrations in water is suspended solids concentration. In sediment, the most significant factors affecting SVOC concentrations are organic carbon content and distance from sources such as highways and power plants. Petroleum hydrocarbons, oil and grease, and polycyclic aromatic hydrocarbons (PAHs) in crankcase oil and vehicle emissions are the major SVOCs detected in highway runoff and urban stormwater. The few loading factors and regression equations that were developed in the 1970's and 1980's have limited use in estimating current (1998) loads of SVOCs on a national scale. These factors and equations are based on few data and use inconsistent units, and some are independent of rainfall. Also, more cars on the road today have catalytic converters, and fuels that were used in 1998 are cleaner than when loading factors and regression equations were developed. Comparisons to water-quality and sediment-quality criteria and guidelines indicate that PAHs, phenolic compounds, and phthalates in runoff and sediment exceeded U.S. Environmental Protection Agency drinking-water and aquatic-life standards and guidelines. PAHs in stream sediments adjacent to highways have the highest potential for adverse effects on receiving streams. Few data exist on VOCs in highway runoff.

Analysis of volatile organic compounds using cryogen-free thermal modulation based comprehensive two-dimensional gas chromatography coupled with quadrupole mass spectrometry

A method for determining 19 volatile organic compounds(VOCs) in innerliner with headspace gas chromatography/mass spectrometry(GC/MS) by using fluorobenzene as an internal standard(ISTD) was established and 20 innerliner samples were tested.The results indicated that: 1) fluorobenzene,was a suitable ISTD for quantitative analysis of these 19 VOCs;2) the recoveries of the VOCs were from 92% to 109% with relative standard deviation(RSD) of less than 4% and the limits of detection between 0.001 and 0.004 mg/m2;3) fewer VOCs were detectable from the samples,the detectable rates of methanol,alcohol,isopropanol,acetone,propylene glycol methyl ether,and ethyl acetate were 90%,100%,100%,100%,55% and 25%,respectively.The residual concentrations of methanol,alcohol and isopropanol were relatively higher,while those of the other 3 VOCs were lower,and total residual concentration was within the limits specified by standard YC 264-2008. Benzene,ethylbenzene,xylene,cyclohexanone,propylene glycol monoethyl ether, 4-methyl-2-pentanone,propyl acetate and isopropyl acetate were not detectable in all samples.Toluene was detected in three samples.

In recent years, microbes and their metabolites are increasingly recognised as key players in the pathogenesis of a wide range of gastrointestinal disorders, such as inflammatory bowel disease (IBD), colorectal cancer, irritable bowel syndrome, and coeliac disease, but also diseases outside the gastrointestinal tract.1, 2 A relatively novel topic in the field of gut metabolomics is the study of faecal volatile organic compounds (VOCs). VOCs are carbon-based molecules and their chemical composition allows for vaporisation at room temperature. They are therefore released as gases from various matrices, such as blood, urine, or faeces, and are responsible for the odour of a substance. In the gut, these compounds primarily result from the metabolic activities of gut microbiota and the intestinal mucosa.3 Alterations in VOC profiles have been described as indicative of various intestinal diseases, including IBD, where specific changes in microbiota composition and diversity, reflected by changes in VOC-profiles, correlate with disease activity.4 Belnour et al. recently conducted a study in a population consisting of 132 case/control pairs of children with IBD and children with gastrointestinal symptoms without IBD.5 Their aim was to compare faecal VOC profiles between both groups, and to assess the relation of faecal VOCs with disease phenotype, localisation, severity, and response to treatment. VOCs were analysed through gas chromatography-mass spectrometry (GC-MS). They observed significantly decreased mean abundance of 43.6% of 62 measured faecal VOCs in IBD patients compared to controls, which is in accordance with the microbial dysbiosis linked with IBD in literature. Propan-1-ol, phenol, and oct-1-en-3-ol, all being alcohols, were the most distinctive VOCs in children with IBD compared to controls. The first two are products of amino acid degradation (threonine, and tyrosine and tryptophan, respectively) by Enterobacteriaceae and Clostridium species, which are often more abundant in IBD.6 The associated amino acids themselves are also linked to gut inflammation.7 The gut microbiome and metabolome have gained scientific interest due to the ongoing quest for new non-invasive biomarkers. Currently, the most used non-invasive biomarker for the detection and monitoring of IBD is faecal calprotectin (FCP), which is characterised by a high sensitivity for identifying disease activity and luminal inflammation, but suffers from low specificity. The reliance on FCP in clinical practice often leads to unnecessary endoscopies which are especially burdensome for children. Consequently, there is a need for novel more accurate non-invasive biomarkers. Belnour et al.'s finding that faecal VOCs could differentiate children with IBD from those with gastrointestinal symptoms without IBD, is significant and aligns with recent literature.8 However, as the authors note, these findings merely provide insights into the pathogenesis of paediatric IBD, and further research is warranted to develop a clinical biomarker. Another critical issue in managing IBD is predicting disease severity and response to therapy. In paediatric IBD, therapeutic guidelines regularly recommend a step-up approach. At baseline, predicting which patients will develop severe disease in the disease course and could benefit from early treatment escalation is challenging. The observation of Belnour et al. of differences in faecal VOC profiles between various states of disease severity and treatment responses is of importance. It highlights the complex pathogenesis of IBD and underscores the need for personalised medical approaches due to the disease's heterogeneity. Advantages of VOC analysis include its speed and relatively low costs. However, challenges include the influence of environmental factors, especially dietary intake, the lack of standardised sampling, storage and handling protocols, and the variety in used analytical techniques.9 GC-MS is considered the gold standard for VOC analysis,10 which separates complex compounds in a GC column, ionises and further separates in the MS column based on mass and transportation time. GC-MS is highly accurate and can identify specific VOCs on molecular level, but is the most expensive, high-maintenance and needs trained personnel to use. Electronic noses (eNoses) are more accessible in terms of costs and time. This technique is based on pattern-recognition of VOC mixtures, allowing for identification of disease-specific VOC patterns, but cannot measure individual VOCs. Though the clinical implementation of faecal VOC analysis is still distant, it holds promise as a potential novel non-invasive biomarker in (paediatric) IBD. Endoscopies will as yet remain necessary for diagnosing IBD to obtain information on disease phenotype, localisation and severity, but faecal VOCs could possibly support to select which patients presenting with gastrointestinal symptoms require endoscopy for suspected IBD diagnosis, given the limited specificity of FCP. Future research should focus on identifying specific VOCs and validating previous results in larger cohorts. The first step however is standardising and refining measurement methodologies to overcome variability in sampling and analysis. The authors have no conflicts of interest to declare. Data sharing is not applicable to this article as no new data were created or analyzed in this study.

The objective was to establish a robust and reliable approach for the characterisation of volatile organic compounds (VOCs) present in food contact paperboard. This was achieved through the utilisation of headspace solid-phase microextraction in tandem with comprehensive two-dimensional (2D) gas chromatography (GC) and quadrupole time-of-flight mass spectrometry (HS-SPME-GC × GC-QTOF-MS). The experimental parameters were optimised, involving the use of a DVB/C-WR/PDMS fibre at a temperature of 80 °C for a duration of 30 min. A total of 344 VOCs comprising aldehydes, ketones, alcohols, ethers, esters, alkanes and aromatic compounds, were tentatively identified in the samples. Twelve compounds believed to be from biogenic sources had a high odour impact making them major contributors to potential taint from the paperboard samples. Significant attention should be devoted to five compounds namely, 2-methylnaphthalene, 2-pentyl-furan, furfural, 1-octen-3-one and 1-octen-3-ol due to their potential adverse impact on the organoleptic qualities of packaged food items and their potential toxicity. Abbreviations: C-WR: carbon wide range; DVB: divinylbenzene; GC-MS: gas chromatography - mass spectrometry; GCxGC-QTOF-MS: comprehensive two-dimensional gas chromatography coupled to quadrupole-time-of-flight - mass spectrometry; HS-SPME: headspace - solid phase microextraction; LOD: limit of detection; LOQ: limit of quantification; OAV: odor activity values; PDMS: polydimethylsiloxane; RI: retention index; TTC: threshold of toxicological concern; VOC: volatile organic compound

The most common technique used to sample streams for volatile organic compounds (VOCs) is dipping volatile organic analysis (VOA) vials by hand midstream. This technique does not assure that samples are collected in a consistent manner. A point sampler was designed to collect samples for the U.S. Geological Survey National WaterQuality Assessment (NAWQA) Program in surface water in a uniform and consistent manner nationwide. This report documents the study design used to evaluate the VOC point sampler, as well as comparative data from glass-siphoning and hand-dipping methods used in the laboratory and field, respectively. Quality-control data collected during the evaluation, specifically source-solution blanks, canister blanks, equipment blanks, and field blanks, also are presented. The study indicates that the VOC point sampler collects samples in a representative manner, as compared to the glass-siphoning and handdipping methods. The relative standard deviation for replicate samples collected by the VOC point sampler was less than 10 percent for 57 of 73 VOCs calculated, indicating a high degree of sample reproducibility. Analyte loss was found to be negligible based, in part, on a comparison of laboratory data to expected recovered concentrations. Furthermore, the cleaning protocol was found to be effective in eliminating any contamination of water samples from the point sampler. INTRODUCTION Ground water has been sampled for the analysis of volatile organic compounds (VOCs) by the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program since 1993. To understand the occurrence of VOCs in other components of the hydrologic cycle, the NAWQA Program began sampling small urban streams for VOCs in 1996. Prior to NAWQA's national emphasis on VOCs, little work had been done within the USGS on VOC field methods or sampling equipment for collecting VOCs from surface water. The most common technique used to sample streams for VOCs is dipping volatile organic analysis (VOA) vials by hand midstream. Consequently, the USGS did not have specific guidelines or a proven sampler to collect VOC samples from surface water. To collect VOC samples from surface water in a uniform and consistent manner nationwide, a surfacewater VOC point sampler was designed by the USGS and Wildlife Supply Company (Wildco) located in Saginaw, Michigan. The sampler (fig. 1) is manufactured by Wildco and is constructed of stainless steel and refrigeration-grade copper. The sampler was designed to collect a sample intended for VOC analysis at a single point in shallow urban streams. The VOC point sampler currently (1998) is being used by NAWQA's study units to collect samples from about 10 urban streams (Lopes and Price, 1997). Guidance on the proper use of the sampler in the field has been developed and documented by Shelton (1997). The purposes of this report are to: (1) document the study design used to evaluate the surface-water VOC point sampler and (2) report the analytical results. This report documents the analytical data

Many recent studies have focused on the connection between the composition of specific volatile organic compounds (VOCs) in exhaled breath and various forms of cancer. However, the composition of exhaled breath is affected by many factors, such as lung disease, smoking, and diet. VOCs are released into the bloodstream before they are exhaled; therefore, the analysis of VOCs in blood will provide more accurate results than the analysis of VOCs in exhaled breath. Blood were collected from 16 colorectal cancer patients and 20 healthy controls, then solid phase microextraction–chromatography–mass spectrometry (SPME-GC-MS) was used to analysis the exhaled volatile organic compounds (VOCs). The statistical methods principal component analysis (PCA) and partial least-squares discriminant analysis (PLSDA) were performed to deal with the final dates. Three metabolic biomarkers were found at significantly lower levels in the group of CRC patients than in the normal control group (P < 0.01): phenyl methylcarbamate, ethylhexanol, and 6-t-butyl-2,2,9,9-tetramethyl-3,5-decadien-7-yne. In addition, significantly higher levels of 1,1,4,4-tetramethyl-2,5-dimethylene-cyclohexane were found in the group of CRC patients than in the normal control group (P < 0.05). Compared with healthy individuals, patients with colorectal adenocarcinoma exhibited a distinct blood metabolic profile with respect to VOCs. The analysis of blood VOCs appears to have potential clinical applications for CRC screening.