Headspace Sampling Research Articles

Analysis of Bacterial Metabolites in Breath Gas of Critically Ill Patients for Diagnosis of Ventilator-Associated Pneumonia—A Proof of Concept Study

Bacterial infection of the lower respiratory tract frequently occurs in mechanically ventilated patients and may develop into life-threatening conditions. Yet, existing diagnostic methods have moderate sensitivity and specificity, which results in the overuse of broad-spectrum antibiotics administered prophylactically. This study aims to evaluate the suitability of volatile bacterial metabolites for the breath-based test, which is used for diagnosing Ventilator-Associated Pneumonia (VAP). The in vitro experiments with pathogenic bacteria most prevalent in VAP etiology (i.e., Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) were performed to identify bacteria-derived metabolites using a specially designed cultivation system enabling headspace sampling for GC-MS analysis. Thirty-nine compounds were found to be significantly metabolized by tested species and, therefore, selected for monitoring in the exhaled breath of critically ill, mechanically ventilated (MV) patients. The emission of volatiles from medical respiratory devices was investigated to estimate the risk of spoiling breath results with exogenous pollutants. Bacterial metabolites were then evaluated to differentiate VAP patients from non-infected MV controls using Receiver Operating Characteristic (ROC) analysis, with AUC, sensitivity, and specificity calculated. Nine bacterial metabolites that passed verification through a non-parametric ANOVA test for significance and LASSO penalization were identified as key discriminators between VAP and non-VAP patients. The diagnostic model achieved an AUC of 0.893, with sensitivity and specificity values of 87% and 82.4%, respectively, being competitive with traditional methods. Further validation could solidify its clinical utility in critical care settings.

Discovery and Validation of a Volatile Signature of Eosinophilic Airway Inflammation in Asthma.

Rationale: Volatile organic compounds (VOCs) in asthmatic breath may be associated with sputum eosinophilia. We developed a volatile biomarker signature to predict sputum eosinophilia in asthma. Methods: VOCs emitted into the space above sputum samples (headspace) from patients with severe asthma (n = 36) were collected onto sorbent tubes and analyzed using thermal desorption gas chromatography-mass spectrometry (GC-MS). Elastic net regression identified stable VOCs associated with sputum eosinophilia ⩾ 3% and generated a volatile biomarker signature. This VOC signature was validated in breath samples from: 1) patients with acute asthma according to blood eosinophilia ⩾0.3 × 109cells/L or sputum eosinophilia of ⩾3% in the UK EMBER (East Midlands Breathomics Pathology Node) consortium (n = 65) and 2) U-BIOPRED-IMI (Unbiased Biomarkers in Prediction of Respiratory Disease Outcomes Innovative Medicines Initiative) consortium (n = 42). Breath samples were collected onto sorbent tubes (EMBER) or Tedlar bags (U-BIOPRED) and analyzed by GC-MS (GC × GC-MS for EMBER or GC-MS for U-BIOPRED). Measurements and Main Results: The invitro headspace identified 19 VOCs associated with sputum eosinophilia, and the derived VOC signature yielded good diagnostic accuracy for sputum eosinophilia ⩾3% in headspace (area under the receiver operating characteristic curve [AUROC] 0.90; 95% confidence interval [CI], 0.80-0.99; P < 0.0001), correlated inversely with sputum eosinophil percentage (rs = -0.71; P < 0.0001), and outperformed fractional exhaled nitric oxide (AUROC 0.61; 95% CI, 0.35-0.86). Analysis of exhaled breath in replication cohorts yielded a VOC signature AUROC (95% CI) for acute asthma exacerbations of 0.89 (0.76-1.0) (EMBER cohort) with sputum eosinophilia and 0.90 (0.75-1.0) in U-BIOPRED, again outperforming fractional exhaled nitric oxide in U-BIOPRED (0.62 [0.33-0.90]). Conclusions: We have discovered and provided early-stage clinical validation of a volatile biomarker signature associated with eosinophilic airway inflammation. Further work is needed to translate our discovery using point-of-care clinical sensors.

Development of the headspace gas chromatography-tandem mass spectrometry method for ethylene oxide and ethylene chlorohydrin residue in medical devices.

Ethylene oxide (EO) sterilization is commonly employed for the sterilization of medical devices and has a very high market share. However, EO and its metabolite ethylene chlorohydrin (ECH) are toxic to humans. In compliance with the classification and residue limits of medical devices defined by ISO 10993-7, our study established two extraction methods for the testing of EO and ECH. The first method involves simulated-use extraction using water as the extraction solvent. While the second, exhaustive extraction, directly extracts sample through headspace sampling analysis. Gas chromatography-tandem mass spectrometry in multiple reaction monitoring mode was utilized, requiring only 16 min. Then, the developed method was applied to assess 10 commercially available medical devices sterilized by EO. In simulated-use extraction, calibration curves were evaluated in the range of 1-100 and 5-500 μg for EO and ECH, respectively (r > 0.999). Inter-day recoveries ranged from 85.0% to 95.2% and from 94.8% to 102.4%. In exhaustive extraction, calibration curves spanned 0.5-50 and 2-200 μg for EO and ECH, respectively (r > 0.999). Inter-day recoveries ranged from 101.6% to 102.1% for EO and from 98.1% to 102.2% for ECH. After analysis of the 10 commercially available medical devices, two cotton swabs were found to have ECH of 35.1 and 28.4μg per device, and four medical devices were found to have EO with concentration below the limit of quantification. Meanwhile, we found that the EO internal standard (propylene oxide) recommended by ISO 10993-7 had interference problems with other similar substances and was not suitable as an internal standard for EO. This study offers a sensitive and straightforward analytical approach to EO and ECH residues in a variety of medical devices. In addition, the results show that the EO or ECH content of these types of medical devices in our study falls below the regulatory limits, therefore instilling confidence among consumers regarding their safe use.

In-tube extraction dynamic headspace coupled to gas chromatography-mass spectrometry for the sensitive analysis of volatile compounds in aqueous samples

Aim: Volatile organic compounds (VOCs) are often human-made contaminants used and generated in the manufacturing of numerous products, presenting notable environmental and health hazards. Therefore, the development of sensitive and reliable analytical methods is crucial for their detection with accuracy, timeliness, and automation capabilities. The objective of this study is to demonstrate the suitability of the in-tube extraction dynamic headspace (ITEX-DHS) sampling method for the gas chromatographic/mass spectrometric (GC/MS) analysis of BTEX (benzene, toluene, ethylbenzene, and xylenes) compounds in aqueous matrices. It emphasizes the method’s metrological reliability and innovative approach to precisely determining VOCs in aqueous environments providing a tool to prevent contamination of the agrifood sector. Methods: Following the optimization of various experimental parameters, including salt incorporation and adjustments of both dry purging and desorption conditions. The method’s performance was evaluated for repeatability, reproducibility, and robustness. Results: Limit of detection (LOD) and limit of quantification (LOQ) were for all substances determined lower than 50 and 100 ng/L, respectively. Average relative standard deviations below 5% were achieved for all analytes, with recovery rates ranging between 93% and 101%. Subsequently, the method was applied for the determination of BTEX in one hundred groundwater samples. The findings revealed that the BTEX levels were below the LOD in 84.2% of samples. However, in the remaining samples, more than one compound was detected at concentrations higher than the LOQ. Conclusions: The ITEX method emerges as a highly favorable alternative to both solid phase microextraction (SPME) and purge and trap (P &amp; T) methods for determining BTEX in aqueous samples, providing significant advantages. Its strengths lie in its increased robustness, extended trap lifespan, and enhanced sensitivity, underscoring its superior performance in VOC analysis. The total analytical method allows the sensitive and robust determination of VOC.

B-148 Bacer: decentralized isotope dilution method with lab blinding for blood alcohol content

Abstract Background In legal medicine, the determination Blood Alcohol Content (BAC) usually faced the problems of insufficient sample size, ethanol degradation and impossible double check. In addition, the integrity of laboratory may also be questioned. To this end, we developed a decentralized solution based on isotope dilution method. Methods Patented deuterated ethanol vacuum tube was used in field as regular type, weight of blood was record to BACer terminal. Arbitrary amount of sample(ca.0.1-1.0g) was pipetted to GC sample vial and sealed tightly, then heated more than 2min at 70°C, 10µL headspace sample was injected into GC-MS. Blinded lab uploaded peak area ratio of ethanol/deuterated ethanol(mz31/33) to BACer to calculate the final BAC. Results Regression between peak area ratios of ethanol/deuterated ethanol showed good linearity in the range of 0.10-5.0 (R2&amp;gt;0.999). Regression equation of different instruments were proved good consistency with slopes ranged from 1.03 to 1.07, and the LOD and LOQ were around 0.01mg/g and 0.05mg/g, 3-level recoveries between 97%-101% with RSD less than 1%. During the 6-month stability test at 4°C and normal temperature, the blood sample test results maintained good stability. The proposed method was applied to 2021 CNAS proficiency testing (2021SF-CNAS002) organized by China Academy of Forensic Sciences with satisfactory results. The comparison with Chinese standard method SF/Z JD0107001-2010 yielded good agreement with Passing&amp;Bablok test (P&amp;gt;0.10). The expanded uncertainty estimated by Monte-carlo method was less than 3%. Conclusions This proposed method showed the possibility of decentralized determination of BAC with lab blinding, the separation of on-site sampling data and laboratory testing also provided the possibility of integrity of results. It also provided a possible solution for the scenarios where the storage condition of blood collection is poor, or the cross check is required. But good chromatographic separation and operation are compulsive due to the possibility of interference in IDMS.

Development of an Untargeted Method for the Analysis of the Volatile Profile of Onions via Solid-Phase Microextraction Arrow-Headspace-Gas Chromatography-Mass Spectrometry Using Design of Experiments.

The distinctive aroma of onions, consisting primarily of sulfur-containing compounds, is one of the reasons for the popularity of the vegetable. The rapid enzymatic and chemical reactions that occur after the destruction of onion bulb tissue render the analysis of the volatile profile challenging. Therefore, sample preparation is a crucial step in the analysis of the onion volatilome, but it often does not receive the necessary attention in the literature. In this work, we focused on two aspects: Firstly, we compared different sample preparation approaches to maximize the volatile yield and to enable the description of the onion volatile profile as it would emerge after a solid-phase microextraction (SPME) Arrow sampling procedure. For headspace (HS)-gas chromatography-mass spectrometry analysis, onion juice with the addition of an ammonium sulfate solution proved to be the best option. Secondly, we optimized the HS sampling and desorption parameters (enrichment time, enrichment temperature, agitator speed, desorption time) for onion volatiles using the efficient design of experiments (DoE) approach. The optimal conditions for the analysis with HS-SPME Arrow were an enrichment time of 75min at 60°C with an agitator speed of 713rpm and a desorption time of 120s.

Analytical Method for the Development and Validation of Residual Solvents in Tigecycline by Gas Chromatography Using Headspace Sampling Technology

Analytical Method for the Development and Validation of Residual Solvents in Tigecycline by Gas Chromatography Using Headspace Sampling Technology

Rapid headspace analysis of commercial spearmint and peppermint teas using volatile 'fingerprints' and an electronic nose.

Spearmint and peppermint teas are widely consumed around the world for their flavor and therapeutic properties. Dynamic headspace sampling (HS) coupled to gas chromatography/mass spectrometry (GC-MS) with principal component analysis (PCA) of 'fingerprint' volatile profiles were used to investigate 27 spearmint and peppermint teas. Additionally, comparisons between mint teas were undertaken with an electronic nose (enose). Twenty compounds, all previously known in the literature, were identified using HS-GC-MS. PCA found distinct differences between the fingerprint volatile profiles of spearmint, peppermint and spearmint/peppermint combination teas. HS-GC-MS analysis performed with an achiral column allowed faster processing time and yielded tighter clustering of PCA tea groups than the analysis which used a chiral column. Two spearmint outliers were detected. One showed a high degree of variation in volatile composition and a second wholly overlapped with the peppermint PCA grouping. Enose analysis separated all treatments with no overlaps. Characterizing the volatile fingerprints of mint teas is critical to quality control for this valuable agricultural product. The results of this study show that fingerprint volatile profiles and enose analysis of mint teas are distinctive and could be used to rapidly identify unknown samples. With specific volatile profiles identified for each tea, samples could be tested in the laboratory, or potentially on a farm or along the supply chain, to confirm the provenance and authenticity of mint food or beverage commodities. © 2024 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Stimulated C2C12 Myotube Headspace Volatile Organic Compound Analysis.

Understanding exercise metabolism and the relationship with volatile organic compounds (VOCs) holds potential in both health care and sports performance. Exercise metabolism can be investigated using whole body exercise testing (in vivo) or through the culture and subsequent electrical pulse stimulation (EPS) of myotubes (in vitro). This research investigates the novel headspace (HS) analysis of EPS skeletal muscle myotubes. An in vitro system was built to investigate the effect of EPS on the volatile constituents in the HS above EPS skeletal muscle. The C2C12 immortalised cell line was chosen. EPS was applied to the system to induce myotube contraction. The in vitro system was applied to the analysis of VOCs using thermal desorption (TD) sampling. Samples were collected under four conditions: environmental samples (enviro), acellular media HS samples (blank), skeletal muscle myotubes without stimulation HS samples (baseline) and EPS of skeletal muscle myotube HS samples (stim). TD sampling combined with gas-chromatography mass spectrometry (GC-MS) detected two compounds that, after multivariate and univariate statistical analysis, were identified as changing due to EPS (p < 0.05). These compounds were tentatively assigned as 1,4-Dioxane-2,5-dione, 3,6-dimethyl- and 1-pentene. The former is a known lactide and the latter has been reported as a marker of oxidative stress. Further research should focus on improvements to the EPS system, including the use of more relevant cell lines, quantification of myotube contractions, and the application of targeted analysis, metabolic assays and media analysis.

Volatile organic compound detection of Buruli ulcer disease: Headspace analysis of Mycobacterium ulcerans and used gauzes of Buruli-compatible ulcers.

Diagnosing Buruli ulcer (BU) is complicated by limited access to the sensitive IS2404 qPCR. Experienced clinicians report a distinct odour of Buruli ulcers. We explored the potential of headspace analysis by thermal desorption-gas chromatography-mass spectrometry to detect volatile organic compounds (VOCs) from Mycobacterium ulcerans both in vitro and clinically. This study was conducted in two phases: a discovery and validation phase. During the discovery phase, VOCs that enable identification of M. ulcerans cultures were determined. During the validation phase, these VOCs were evaluated in clinical samples for which we used gauzes from patients with skin ulcerations in the Democratic Republic of Congo. Seven M. ulcerans headspace samples were compared with four from sterile growth medium and laboratory environmental air. The univariate analysis resulted in the selection of 24 retained VOC fragments and a perfect differentiation between cultures and controls. Sixteen of 24 fragments were identified, resulting in eleven unique compounds, mainly alkanes. Methylcyclohexane was the best performing compound. Based on these 24 fragments, headspace samples originating from gauzes of 50 open skin lesions (12 qPCR positive and 38 negative) were analysed and an AUC of 0.740 (95%-CI 0.583-0.897) was obtained. As this is an experimental study, future research has to confirm whether the identified compounds can serve as novel biomarkers.

A headspace injection double-column dual-detector gas chromatography system for the analysis of 12 volatile compounds such as ethanol in human blood

Based on the technical methods of GB/T 42430-2023 and GA/T 204-2019, this study established an analytical method for headspace injection double-column dual-detector (hydrogen flame ion detector) gas chromatography for the simultaneous analysis of at least 12 volatile compounds, including ethanol, in human blood using two different equipment platforms and chromatographic columns. A 100 μL blood or urine sample and a 0.04 g/L tert-butanol working solution prepared as an internal standard are introduced into the headspace sample bottle and then sealed, mixed, and placed on the headspace sampler rack. Using different equipment platforms and columns, methodological parameters such as the limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy of the method were systematically evaluated. The chromatographic separation of acetone, alcohols and benzenes using the established method was satisfactory. The linear ranges, linear correlation coefficients (r), and LODs of acetone and six alcohols, including ethanol, were 0.10-3.00 g/L, >0.997, and 0.05 g/L, respectively. The LOQs were 0.10 g/L for all other compounds, excluding n-propanol (0.005 g/L). Additionally, the linear ranges, r values, LODs, and LOQs of benzene and four benzene derivatives were 0.05-50 mg/L, >0.995, 0.02 mg/L, and 0.05 mg/L, respectively (Column J&W DB-BAC1 UI and Column Rtx-BAC-PLUS 2). The average recoveries of compounds on J&W DB-BAC1 UI and Rtx-BAC-PLUS 2 columns ranged from 92.2% to 111.6%, and the relative standard deviations (RSDs, n=6) ranged from 0.4% to 7.4%. The LOD, LOQ, precision, accuracy, and linearity of the established method met the requirements of relevant standards, and no significant differences arose between the methodological parameters of the two platforms. CNAS-GL006 (2019) and JJF 1059.1-2012 were used as guides to evaluate the uncertainty of ethanol on two different sets of equipment platforms and chromatographic columns. The ethanol uncertainty was mainly derived from the calibration curve; however, the confidence probability was 95% (k=2). According to the analysis of the verification samples and real samples, the established method is suitable for the high-precision quantitative analysis of acetone and six alcohols and five benzene derivatives in human blood and other body fluids. It can be used in practical scenarios such as judicial identification and the detection of poisons.

Olfactory Response of Sitophilus zeamais Adults to Odours of Semolina Pasta and Semolina Pasta Enriched with Different Amounts of Acheta domesticus Powder.

The behavioural response of adult maize weevil, Sitophilus zeamais, to different types of semolina pasta enriched or not enriched with increasing proportions (5%, 10%, and 15%) of house cricket (Acheta domesticus) powder was investigated in olfactometer arena bioassays by using trap devices. In the five-choice behavioural bioassays, the number of S. zeamais adults attracted to 100% durum wheat semolina pasta was significantly higher than those attracted to the other pasta types enriched with A. domesticus powder. In the two-choice behavioural bioassays, the Response Index for each pasta type was positive and significant. However, although not significant, there was a progressive reduction in the Response Index as the cricket powder content increased. In similar experiments, there were no significant differences between cricket powder alone and the control in the number of attracted S. zeamais, indicating a neutral effect towards insects. These observations suggest that the lower attractiveness of pasta enriched with house cricket powder is mainly due to the masking of host food odours. Solid-phase microextraction coupled to gas chromatography-mass spectroscopy identified a total of 18 compounds in the head-space samples of the different types of pasta, highlighting differences in volatile composition. Some volatile compounds were only present in the pasta produced with cricket powder. In particular, 1-octen-3-ol and phenol were present in the samples containing 5%, 10%, or 15% cricket powder; pentanal, benzaldehyde, and dimethyl disulphide were present in samples containing 10% or 15% cricket powder; and 2,5-dimethyl-pyrazine was present in the sample containing 15% cricket powder. Further investigation with individual compounds and mixtures is needed to define the chemical basis of the differences in the insect olfactory preference observed in this study.

Pursuing drug laboratories: Analysis of drug precursors with High Kinetic Energy Ion Mobility Spectrometry

High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS) is a technique for rapid and reliable detection of trace compounds down to ppbV-levels within one second. Compared to classical IMS operating at ambient pressure and providing the ion mobility at low electric fields, HiKE-IMS can also provide the analyte-specific field dependence of the ion mobility and a fragmentation pattern at high reduced electric field strengths. The additional information about the analyte obtained by varying the reduced electric field strength can contribute to reliable detection. Furthermore, the reduced number of ion-molecule reactions at the low operating pressure of 10 – 40 mbar and the shorter reaction times reduce the impact of competing ion-molecule reactions that can cause false negatives. In this work, we employ HiKE-IMS for the analysis of phenyl-2-propanone (P2P) and other precursor chemicals used for synthesis of methamphetamine and amphetamine. The results show that the precursor chemicals exhibit different behavior in HiKE-IMS. Some precursors form a single significant ion species, while others readily form a fragmentation pattern. Nevertheless, all drug precursors can be distinguished from each other, from the reactant ions and from interfering compounds. In particular, the field-dependent ion mobility as an additional separation dimension aids identification, potentially reducing the number of false positive alarms in field applications. Furthermore, the analysis of a seized illicit P2P sample shows that even low levels of P2P can be detected despite the complex background present in the headspace of real samples.

PFAS emissions from functional textiles using micro-chamber and thermal desorption coupled to two-dimensional gas chromatography-time of flight mass spectrometry (TD-GC×GC-TOF MS)

Per- and polyfluoroalkyl substances (PFAS), in the polymeric form, have been used extensively in functional textiles, including firefighter's turnout gear (e.g., jackets and pants), where PFAS are applied to confer oil and water resistance. However, growing concerns over the persistence, potential toxicity, and environmental impact of PFAS have prompted a thorough assessment of potential exposure pathways. Here, we report the emission of PFAS from three firefighter turnout gear jackets at 38 °C. Volatile emissions from the three layers (outer layer, moisture barrier, and thermal liner) were collected onto sorbent tubes via dynamic headspace sampling using a micro-scale chamber device kept at 38 °C for one hour. The emission was characterized using thermal desorption (TD) coupled to two-dimensional gas chromatography - time-of-flight mass spectrometry (GC×GC–TOF MS). The enhanced separation capacity of GC×GC was essential due to the high number of compounds present in each sample, especially for the fabrics from used turnout gear jackets. Based on the filtering expressions, including two-dimensional retention time (1tr and 2tr) and PFAS diagnostic fragment ions (m/z 69, 95, and 131), fluorotelomer alcohols (FTOHs) and fluorotelomer acrylates were identified using standards and spectral matching with the NIST database. After conducting a non-targeted tile-based workflow, jackets (both used and unused) and layers were compared, resulting in the identification of the top 15 discriminating features from over 400 chromatographic peaks. Finally, preliminary FTOH emission experiments showed some usage and layers trends that are aligned with those reported using solvent extraction. Highest levels of FTOHs were found in the moisture barrier, followed by the outer layer and the thermal liner. Older jackets emitted higher levels of 8:2 FTOH and 10:2 FTOH than a newer jacket. In contrast, a newer jacket used for one year had emissions containing higher levels of 6:2 FTOH. Investigating routes of exposure and identifying new PFAS targets are critical steps in evaluating the environmental and health impacts of these persistent chemicals.

From Gas to Gas: Fundamentals of Static Headspace Extraction-Gas Chromatography

Headspace sampling is one of the staple sample introduction techniques for gas chromatography (GC) because it involves the injection of samples already in the vapor phase into the instrument. In this installment, we discuss the fundamentals of headspace extraction, including static versus dynamic extraction, establishing equilibrium in the vial, consequences of the partition coefficient, temperature, pressure, and transfer to the gas chromatograph. We see how, with consideration of the fundamental chemical equilibria involved, headspace extraction with GC can be one of the simplest yet most powerful and versatile chromatographic techniques.

Optimization of headspace high-capacity tool coupled to two-dimensional gas chromatography–mass spectrometry for mapping the volatile organic compounds of raw pistachios. A proof-of-concept on the classification ability by geographic origin

An optimized procedure for extracting and analyzing raw pistachio volatiles was developed through headspace sampling with high-capacity tools and subsequent analysis using comprehensive two-dimensional gas chromatography coupled with mass spectrometry. The examination of 18 pistachio samples belonging to different geographic areas led to the identification of a set of 99 volatile organic compounds (VOCs). Molecules were putatively identified using linear retention index, mass spectra similarity, and two-dimensional plot location. The impact of preprocessing and processing techniques on the aligned data matrix from a set of samples of different geographical origins, after removing contaminants, was evaluated. The combination of scaling with log-transformation, normalization with z-score, and data reduction with random forest machine learning algorithm generated a panel of 16 discriminatory VOC molecules. As a proof of concept, raw pistachios' VOC profile was employed for the first time to tentatively classify them based on their geographical origin.

Characterisation of aroma‐active compounds in wheat flour by molecular sensory science

SummaryFour different extraction methods were used to extract aroma compounds from flour. It was found that dynamic headspace sampling (DHS) was a better method for extracting aroma‐active compounds in flour. Hexanal, decanal, butanoic acid, 2,3‐pentanedione, 2‐acetyl‐1‐pyrrolinoline, and 3‐octen‐2‐one were found to be the important aroma‐active compounds in flour by olfaction (O) in two‐dimensional gas chromatography–olfactometry–mass spectrometry (GC×GC‐O‐MS). Dynamic headspace dilution analysis (DHDA), odour activity value (OAV), recombination and omission experiment further verified that these compounds can roughly simulate the overall aroma profile of flour. In this study, we determined the aroma‐active compounds in flour by molecular sensory science to improve the sensory preference of flour and enhance the quality of flour aroma, which will provide analytical ideas for future research on flour aroma and improve the production process.

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.

Optimization of Dynamic Headspace Sampling Conditions for the Identification of Paleolithic Adhesives

ABSTRACTThe characterization of Paleolithic adhesives holds great potential for understanding human behavior and its evolution. Gas chromatography–mass spectrometry (GC–MS) is the most accurate identification method; unfortunately, it is destructive and requires a large sample size. Hence, most Paleolithic adhesives are not characterized with GC–MS. Here, a new nondestructive identification method is introduced; dynamic headspace (DHS) with two‐dimensional GC coupled to a time‐of‐flight MS. The DHS extraction is optimized with an experimental design approach. Four parameters were selected, and the optimized values were as follows: incubation temperature: 50°C, incubation time: 20 min, purge volume: 450 mL, and purge flow: 22.5 mL min−1, pine resin was chosen as a proxy for Paleolithic adhesives. Subsequently, DHS was also tested on hide glue, which has less volatile than pine resin, and the universality of the extraction was tested. With untargeted techniques, a distinction between hide glue and pine resin could be made based on their chromatographic profiles. Lastly, DHS was tested against an existing HS‐solid‐phase microextraction method. DHS showed a higher response in the total area of the chemical groups of interest. Thus, DHS has a higher sensitivity for prehistoric adhesives than solid‐phase microextraction, which is desired for minimal samples.

Remediation of Sulfides in Produced Waters of the Oil and Gas Industry Using Hydrogen Peroxide

Produced waters are often treated in open lagoons where hydrogen sulfide (H2S) can off gas, posing a risk to human health and the environment. The aim of this study was to optimize a treatment process using hydrogen peroxide (H2O2) to oxidize H2S while minimizing off gassing. Samples of produced water from West Texas and laboratory-prepared waters utilizing sodium sulfide (Na2S) or biogenic polysulfides were oxidized with H2O2 alone or in combination with copper or iron catalysts, sodium hydroxide (NaOH), or a commercial sulfide oxidizer, HydroPower Green™. Sulfur speciation was measured using Hach test kits for sulfide/sulfate/sulfite and Dräger tubes for headspace H2S. HydroPower Green™ (HPG) helped to reduce H2S in the headspace of water samples; some of this was pH related as NaOH also worked, but not as well as HPG. The dose of peroxide necessary to oxidize sulfides to sulfate is a function of the oxidation-reduction potential (Eh) of the water and total sulfide concentration as well as pH; approximately a 1–4:1 ratio of peroxide to sulfide concentration was needed to oxidize sulfidic waters of pH 7–10 with half-lives under 30 min. Both copper and iron catalysts reduce H2O2 demand and the half-life of H2S. Peracetic acid (PAA) and copper (II) sulfate pentahydrate (CuSO4, 5H2O) were explored as biocides for controlling sulfate-reducing bacteria (SRBs) that produce H2S. An AquaSnap (Hygenia) test kit was employed to monitor relative microbial activity in a wetland porewater containing H2S. Microbial regrowth occurred after a few days using the highest dose of PAA; these results showed that PAA was being used by bacteria as a carbon source even after the initial substantial reduction in the microbial activity. CuSO4, 5H2O at a dose of 1 ppm prevented microbial regrowth. The recommended treatment process from this research is determined by jar testing with H2O2, a base for pH control, a biocide, and possibly a metal catalyst or other co-oxidants in order to achieve oxidation of sulfides without H2S release or the precipitation of metal carbonates or oxides.