Determination of volatile organic compounds in water by headspace solid-phase microextraction gas chromatography coupled to tandem mass spectrometry with triple quadrupole analyzer

Rapid differentiation of cystic fibrosis-related bacteria via reagentless atmospheric pressure photoionisation mass spectrometry

Breath analysis is an area of significant interest in medical research as it allows for non-invasive sampling with exceptional potential for disease monitoring and diagnosis. Volatile organic compounds (VOCs) found in breath can offer critical insight into a person's lifestyle and/or disease/health state. To this end, the development of a rapid, sensitive, cost-effective and potentially portable method for the detection of key compounds in breath would mark a significant advancement. Herein, we have designed, built and tested a novel reagent-less atmospheric pressure photoionisation (APPI) source, coupled with mass spectrometry (MS), utilising a bespoke bias electrode within a custom 3D printed sampling chamber for direct analysis of VOCs. Optimal APPI-MS conditions were identified, including bias voltage, cone voltage and vaporisation temperature. Calibration curves were produced for ethanol, acetone, 2-butanone, ethyl acetate and eucalyptol, yielding R2 > 0.99 and limits of detection < 10 pg. As a pre-clinical proof of concept, this method was applied to bacterial headspace samples of Escherichia coli (EC), Pseudomonas aeruginosa (PSA) and Staphylococcus aureus (SA) collected in 1 L Tedlar bags. In particular, PSA and SA are commonly associated with lung infection in cystic fibrosis patients. The headspace samples were classified using principal component analysis with 86.9% of the total variance across the first three components and yielding 100% classification in a blind-sample study. All experiments conducted with the novel APPI arrangement were carried out directly in real-time with low-resolution MS, which opens up exciting possibilities in the future for on-site (e.g., in the clinic) analysis with a portable system.

Air quality assessment in biosphere reserves close to emission sources. The case of the Spanish "Tablas de Daimiel" national park

This work shows that biosphere reserves, national parks and other protected natural areas require in situ tools to monitor and detect local and remote air pollution sources which are a threat to flora, fauna water and soil. Industries in surrounding areas, traffic and long-range transport of air pollution, can change with time and meteorology and so each national park should also have a historical database of the air quality in the site. This study reports surface measurements of ozone, NO, NO₂, CO, SO₂ and PM_2.5 acquired from March 2020 to July 2021 in "Las Tablas de Daimiel", a wetland Mediterranean National Park bordered by different cities and new industries in the field of the revalorization of agricultural wastes. Simultaneous data from a background station in a rural area isolated from air pollution are considered as reference. Twelve campaigns of one week duration were also performed to sample air in sorbent tubes to analyse volatile organic compounds from anthropogenic sources. Data are discussed considering meteorology, especially wind speed and direction together with the assessment of back-trajectories of air masses from distant sources. The results show that the effects of pollution from local and faraway sources on air quality in the park were weak. Thus, except for the high levels of ozone, with a mean value of 71 μg.m^-3, measured mass loadings for pollutants were low and not in exceedance of the air quality standards. Saharan dust events were frequent and contributed to PM_2.5 levels in the site. NO_x and SO₂ average concentrations (3.2 and 0.4 μg.m^-3, respectively) were below the recommended critical levels for vegetation and all the quantified VOCs were found in average concentration levels below 0.5 μg.m^-3.

Volatile organic compounds in water matrices: Recent progress, challenges, and perspective

Volatile organic compounds (VOCs) are a group of organic compounds that have a molecular structure containing carbon and their chemical properties allow them to be easily converted to steam and gas and remain for a long period of time and have diverse effects on the environment. The purpose of this study is determination of the concentration of VOCs such as alachlor, anthracene, benzene, bromoform, chloroform, heptachlor, isophorone, tetrachloroethylene, γ -chlordane, toluene, etc. in water matrices. The results showed that among studies conducted on VOCs, the concentration of tetrachloroethylene, m,p-xylene, and toluene were at the top in water matrices, and the lowest average concentrations were found in chloroform, anthracene, and butyl benzyl phthalate. In terms of VOC concentrations in water matrices, China was the most polluted country. Moreover, the data analysis indicated that China was the only country with carcinogenic risk. A Monte-Carlo simulation showed that although the averages obtained were comparable to the acceptable limits, for heptachlor, the maximum carcinogenic risk is achieved at a level that is slightly over the limit, only 25% from the population being exposed.

Toward Chalcogenide Platform Infrared Sensor Dedicated to the In Situ Detection of Aromatic Hydrocarbons in Natural Waters via an Attenuated Total Reflection Spectroscopy Study

The objective of this study is to demonstrate the successful functionalization of the surface of a chalcogenide infrared waveguide with the ultimate goal of developing an infrared micro-sensor device. First, a polyisobutylene coating was selected by testing its physico-chemical compatibility with a Ge-Sb-Se selenide surface. To simulate the chalcogenide platform infrared sensor, the detection of benzene, toluene, and ortho-, meta- and para-xylenes was efficaciously performed using a polyisobutylene layer spin-coated on 1 and 2.5 µm co-sputtered selenide films of Ge₂₈Sb₁₂Se₆₀ composition deposited on a zinc selenide prism used for attenuated total reflection spectroscopy. The thickness of the polymer coating was optimized by attenuated total reflection spectroscopy to achieve the highest possible attenuation of water absorption while maintaining the diffusion rate of the pollutant through the polymer film compatible with the targeted in situ analysis. Then, natural water, i.e., groundwater, wastewater, and seawater, was sampled for detection measurement by means of attenuated total reflection spectroscopy. This study is a valuable contribution concerning the functionalization by a hydrophobic polymer compatible with a chalcogenide optical sensor designed to operate in the mid-infrared spectral range to detect in situ organic molecules in natural water.

Optimization and validation of headspace solid-phase microextraction method coupled with gas chromatography-triple quadrupole tandem mass spectrometry for simultaneous determination of volatile and semi-volatile organic compounds in coking wastewater treatment plant

Industrial wastewater could be an important source for the emission of volatile (VOCs) and semi-volatile organic compounds (SVOCs), but little is known about it. In this study, a method for the identification and quantitation of 43 VOCs and SVOCs in coking wastewater was developed using a solvent-free equilibrium extraction method on the basis of headspace solid-phase microextraction accompanied by gas chromatography-triple quadrupole tandem mass spectrometry (HS-SPME-GC-MS/MS). To ensure good extraction efficiency, the parameters that have an effect on the HS-SPME-GC-MS/MS process were carefully optimized, in terms of fiber exposure time and temperature, pH, salt additives, sample volume, and desorption time. The HS-SPME method showed good linearity range with coefficients of determination (R²) ≥ 0.991 and achieving a satisfactory recoveries value (70-120%) with good relative standard deviations (RSDs) < 20% (precision). Furthermore, the purposed approach proved to be sensitive with low detection limits, where the values ranged from 0.03 to 3.01 μg/L. The real sample analysis result showed that 43 of VOCs and SVOCs were detected in raw coking wastewater, with 3-cresol as the dominant ones. Further, the method revealed that seven phenols, 11 polycyclic aromatic hydrocarbons, and five BTEX were detected even in the treated effluent. In conclusion, the HS-SPME method developed in this study is simple in sample preparation, convenient, sensitive, and could satisfy the requirement of the analysis of VOCs and SVOCs in coking wastewater.

Characterisation and cleaning of biogas from sewage sludge for biomethane production

This study investigates the conversion of sewage sludge from wastewater treatment plants (WWTP) into biomethane for automotive fuel or grid injection. A prototype plant was monitored in Northern Italy, based on vacuum swing adsorption (VSA) on synthetic zeolite 13×: this biogas upgrading method is similar to pressure swing adsorption (PSA) and commonly used for other kinds of biomass. Measurements of biogas inlet, biomethane outlet and off-gas were performed including CH₄, CO₂, CO, H₂, O₂, N₂, HCl, HF, NH₃, H₂S and volatile organic compounds (VOCs). Critical levels were observed in the biogas for of H₂S and HCl, whose concentrations were 1570 and 26.8 mg m^-3, respectively. On the other hand, the concentration of halogenated VOCs (including tetrachloroethylene and traces of perfluoroalkilated substances, PFAS) and mercaptans were relatively low. A simultaneous and reversible adsorption on 13× zeolite was achieved for H₂S and CO₂, and carbon filters played a minor role in desulfurisation. The presence of HCl is due to clarifying agents, and its removal is necessary in order to meet the required biomethane characteristics: an additional carbon-supported basic adsorbent was successfully used to remove this contaminant. This study also highlights the interference of CO₂ towards HCl if sampling is performed in compliance with the new EU standard for biomethane. High total volatile silicon (TVS) was confirmed in sewage sludge biogas, with a major contribution of siloxane D5: the suitability of this compound as an indicator of total siloxanes is discussed. Results demonstrate that volatile methyl siloxanes (VMS) do not represent a critical issue for the VSA upgrading methodology.

Optimizing Mass Spectrometry Analyses: A Tailored Review on the Utility of Design of Experiments

Mass spectrometry (MS) has emerged as a tool that can analyze nearly all classes of molecules, with its scope rapidly expanding in the areas of post-translational modifications, MS instrumentation, and many others. Yet integration of novel analyte preparatory and purification methods with existing or novel mass spectrometers can introduce new challenges for MS sensitivity. The mechanisms that govern detection by MS are particularly complex and interdependent, including ionization efficiency, ion suppression, and transmission. Performance of both off-line and MS methods can be optimized separately or, when appropriate, simultaneously through statistical designs, broadly referred to as "design of experiments" (DOE). The following review provides a tutorial-like guide into the selection of DOE for MS experiments, the practices for modeling and optimization of response variables, and the available software tools that support DOE implementation in any laboratory. This review comes 3 years after the latest DOE review (Hibbert DB, 2012), which provided a comprehensive overview on the types of designs available and their statistical construction. Since that time, new classes of DOE, such as the definitive screening design, have emerged and new calls have been made for mass spectrometrists to adopt the practice. Rather than exhaustively cover all possible designs, we have highlighted the three most practical DOE classes available to mass spectrometrists. This review further differentiates itself by providing expert recommendations for experimental setup and defining DOE entirely in the context of three case-studies that highlight the utility of different designs to achieve different goals. A step-by-step tutorial is also provided.

Determination of volatile chlorinated hydrocarbons in water samples by static headspace gas chromatography with electron capture detection

A simple, efficient, solvent-free, and commercial readily available approach for determination of five volatile chlorinated hydrocarbons in water samples using the static headspace sampling and gas chromatography with electron capture detection has been described. The proposed static headspace sampling method was initially optimized and the optimum experimental conditions found were 10 mL water sample containing 20% w/v sodium chloride placed in a 20 mL vial and stirred at 50ºC for 20 min. The linearity of the method was in the range of 1.2-240 μg/L for dichloromethane, 0.2-40 μg/L for trichloromethane, 0.005-1 μg/L for perchloromethane, 0.025-5 μg/L for trichloroethylene, and 0.01-2 μg/L for perchloroethylene, with coefficients of determination ranging between 0.9979 and 0.9990. The limits of detection were in the low μg/L level, ranging between 0.001 and 0.3 μg/L. The relative recoveries of spiked five volatile chlorinated hydrocarbons with external calibration method at different concentration levels in pure, tap, sea water of Jiaojiang Estuary, and sea water of waters of Xiaomendao were in the range of 91-116, 96-105, 86-112, and 80-111%, respectively, and with relative standard deviations of 1.9-3.6, 2.3-3.5, 1.5-2.7, and 2.3-3.7% (n = 5), respectively. The performance of the proposed method was compared with traditional liquid-liquid extraction on the real water samples (i.e., pure, tap, and sea water, etc.) and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of volatile chlorinated hydrocarbons in different water samples.

A naphthalimide-based fluorescent sensor for halogenated solvents

AMNis the first sensor to have the ability to differentiate CCl₄, CHCl₃, CH₂Cl₂and CHBr₃from halogenated solvents.

New trends in sample preparation techniques for environmental analysis

Environmental samples include a wide variety of complex matrices, with low concentrations of analytes and presence of several interferences. Sample preparation is a critical step and the main source of uncertainties in the analysis of environmental samples, and it is usually laborious, high cost, time consuming, and polluting. In this context, there is increasing interest in developing faster, cost-effective, and environmentally friendly sample preparation techniques. Recently, new methods have been developed and optimized in order to miniaturize extraction steps, to reduce solvent consumption or become solventless, and to automate systems. This review attempts to present an overview of the fundamentals, procedure, and application of the most recently developed sample preparation techniques for the extraction, cleanup, and concentration of organic pollutants from environmental samples. These techniques include: solid phase microextraction, on-line solid phase extraction, microextraction by packed sorbent, dispersive liquid-liquid microextraction, and QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe).

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 ∼0.3 ppbV; that of benzene is well below the present European Union permissible exposure limit for benzene vapor (5 μg m(-3), ∼1.44 ppbV), 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.

Certified reference material of volatile organic compounds for environmental analysis: BTEX in methanol

The Brazilian Metrology Institute (National Institute of Metrology, Quality, and Technology, Inmetro) has been developing a certified reference material (CRM) of the volatile organic compounds benzene; toluene; ethylbenzene; and ortho, meta, and para-xylenes (BTEX) in methanol, to ensure quality control for environmental-analysis measurements. The objective of this paper is to present the results of certification studies: uncertainty estimates related to characterization, a homogeneity study, and a stability study on a single lot of CRM composed of BTEX in methanol. The method used analysis of variance (ANOVA), a statistical tool, to evaluate the homogeneity and stability of the BTEX CRM, which complies with ISO Guide 30 series. The homogeneity and stability of the BTEX CRM was confirmed for all analytes and their respective properties. All the procedures used in this study complied with ISO GUIDE 34, ISO GUIDE 35, and the guide to the expression of uncertainty of measurement (GUM).

Study of the influence of temperature and precipitations on the levels of BTEX in natural waters

Assessment of seasonal changes in surface water quality is an important aspect for evaluating temporal variation of water due to natural or anthropogenic inputs of point and non-point sources. The objective of this paper was to investigate the influence of seasonal temperature fluctuations and precipitations on the levels of BTEX in natural waters. Principal component analysis (PCA) was used to evaluate the seasonal correlations of BTEX levels in water and to extract the parameters that are most important in assessing seasonal variations of water quality. This study was carried out as a part of VOCs monitoring program in natural water samples from Mediterranean coast. To carry out this project, a multiresidue analytical method was used. The method was based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography coupled to flame ionization detector (FID). The limits of detection LODs found for the tested analyte tested were in the 0.001-1 μg/L range. These values were adequate for the analysis of these compounds in water samples according to the regulated values. Water samples from different points of the Mediterranean coast were analyzed during a period of three years, and were taken four times per year. Most of the compounds were below the limit established by the legislation. The results obtained by a chemometric study indicated that temperature and precipitations can be related on the BTEX levels found in water. A regression model between temperature or precipitations and BTEX concentration was obtained, thus these models can be used as predictive model for detection any non-normal concentration level.