Ion Flow Tube Mass Spectrometry Research Articles

Volatile compounds released by Nalophan; implications for selected ion flow tube mass spectrometry and other chemical ionisation mass spectrometry analytical methods.

Three analytical techniques were used to analyse the VOCs released into the nitrogen used to expand Nalophan bags, viz. gas chromatography/mass spectrometry (GC/MS), secondary electrospray ionization mass spectrometry (SESI-MS) and selected ion flow tube mass spectrometry (SIFT-MS). The most significant VOCs were identified and quantified by SIFT-MS as a function of storage time, temperature and humidity. The consistent results obtained by these three analytical methods identify 1,2-ethanediol (ethylene glycol) and 2-methyl-1,3-dioxolane as the major VOCs released by the Nalophan. Their concentrations are enhanced by increasing the bag storage temperature and time, reaching 170 parts-per-billion by volume (ppbv) for ethylene glycol and 34 ppbv for 2-methyl-1,3-dioxolane in humid nitrogen (absolute humidity of 5%) contained in an 8-L Nalophan bag stored at 37°C for 160 min. Using H3 O+ reagent ions for SIFT-MS and SESI-MS analyses, the following analyte ions (m/z values) are affected by the Nalophan impurities: 45, 63, 81, 89 and 99, which can compromise analyses of acetaldehyde, ethylene glycol, monoterpenes, acetoin, butyric acid, hexanal and heptane.

Thermal Degradation of p‐Hydroxybenzoic Acid in Macadamia Nut Oil, Olive Oil, and Corn Oil

Abstractp‐Hydroxybenzoic acid (PHBA) plays a significant role in sustaining the oxidative stability of macadamia nut oil (MNO). However, PHBA undergoes thermal decarboxylation and loses its bioactive antioxidant properties. In this study, we determine PHBA degradation kinetics in oils at various heating temperatures, which provides fundamental understanding of PHBA thermal degradation in oils and oil quality changes during high‐temperature processing. PHBA degradation kinetics in MNO, olive oil, and corn oil were evaluated at temperatures typical for cooking and frying. PBHA headspace concentration was measured using selected ion flow tube mass spectrometry. PHBA decarboxylation followed a zero‐order reaction, where degradation could be affected by factors such as the type of oil matrix having different FA compositions, antioxidants, and component interactions. PHBA degradation activation energies (E a) showed that PHBA was more stable against thermal decarboxylation in MNO (85 kJ mol–1) than in olive oil (40 kJ mol−1) or corn oil (22 kJ mol−1). The higher enthalpy () of decarboxylation in MNO (82 kJ mol−1) indicates that PHBA is more inhibited from decomposition than olive oil (37 kJ mol−1) or corn oil (19 kJ mol−1). Moreover, the negative entropy values () of PHBA degradation from MNO (−192 J mol−1 K−1), olive oil (−277 J mol−1 K−1), and corn oil (−325 J mol−1 K−1) indicates that these oils impart some inhibitory properties against PHBA thermal decarboxylation.

Ion chemistry of phthalates in selected ion flow tube mass spectrometry: isomeric effects and secondary reactions with water vapour.

Phthalates are widely industrially used and their toxicity is of serious environmental and public health concern. Chemical ionization (CI) analytical techniques offer the potential to detect and monitor traces of phthalate vapours in air or sample headspace in real time. Promising techniques include selected ion flow tube mass spectrometry (SIFT-MS), proton transfer reaction mass spectrometry (PTR-MS) and ion mobility spectrometry (IMS). To facilitate such analyses, reactions of H3O+, O2+ and NO+ reagent ions with phthalate molecules need to be understood. Thus, the ion chemistry of dimethyl phthalate isomers (dimethyl phthalate, DMP - ortho; dimethyl isophthalate, DMIP - meta; dimethyl terephthalate, DMTP - para), diethyl phthalate (DEP), dipropyl phthalate (DPP) and dibutyl phthalate (DBP) was studied by SIFT-MS. Reactions of H3O+, O2+ and NO+ with these phthalate molecules M were found to produce the characteristic primary ion products MH+, M+ and MNO+, respectively. In addition, a dissociation process forming the (M-OR)+ fragment was observed. For phthalates with longer alkyl chains, mainly DPP and DBP, a secondary dissociation channel triggered by the McLafferty rearrangement was also observed. However, this is dominant only for the more energetic O2+ reactions with phthalates, additionally resulting in a recognisable formation of the protonated phthalate anhydride. For the NO+ reagent ions, the McLafferty rearrangement makes only a minor contribution and for H3O+, it was not observed. Experiments on the effect of water vapour on this ion chemistry have shown that protonated DMIP and DMTP efficiently associate with H2O forming the DMIP·H+H2O, DMIP·H+(H2O)2 and DMTP·H+H2O cluster ions, whilst the protonated ortho DMP isomer as well as other ortho phthalates DEP, DPP and DBP does not associate with H2O. The results indicate that the degree of hydration can be used to identify specific phthalate isomers in CI.

Ex vivo detection and quantification of apically extruded volatile compounds and disinfection by-products by SIFT-MS, during chemomechanical preparation of infected root canals

ObjectivesTo assess the release and apical extrusion of toxic volatile compounds and disinfection by-products during instrumentation and irrigation of artificially infected root canal specimens, with sodium hypochlorite and ethylene diamine tetra acetic acid. MethodsForty-two single-rooted human teeth were decoronated to obtain 15mm-long root specimens and working length was determined 1mm short of root apex. All specimens were initially preflared, to create sufficient conical space for the development of a nutrient-stressed multispecies biofilm. The specimens were randomly assigned into three groups [Group 1; no endodontic intervention, Group 2; instrumentation with rotary files and irrigation with sterile saline, Group 3; instrumentation with rotary files and irrigation with 2.5% sodium hypochlorite (NaOCl) and 17% ethylene diamine tetra acetic acid (EDTA)]. A customised experimental model apparatus was fabricated for each specimen. The apical root third was inserted in a glass vial filled with sterile ultrapure water, to simulate high-compliance periradicular space. The reaction products of the aliquots obtained from the glass vials were analysed in real time, by selected ion flow tube mass spectrometry (SIFT-MS) in triplicates. Two-way analysis of variance (ANOVA) with post hoc Tukey tests were used for data analysis. The level of statistical significance was set at P<0.05. ResultsThe group of teeth that were not subjected to endodontic intervention did not show any volatile compounds (VOCs) or disinfection by products (DBPs) whilst instrumentation and irrigation of root canals (Groups 2 and 3) resulted in the apical extrusion of VOCs and DBPs. In Group 3, the aliquots obtained from periradicular space released high concentrations of methanol, propanol, ammonia, chloroform, together with unexpected higher levels of formaldehyde, which were statistically significant compared to Group 2 (P<0.05). SignificanceThe mechanical preparation and irrigation of artificially infected root canals with rotary files, 2.5% NaOCl and 17% EDTA resulted in the formation of toxic VOCs and DBPs in a water-closed periradicular space. The chemical interaction of NaOCl and EDTA resulted in the generation of high concentrations of formaldehyde. The formation of chloroform and formaldehyde indicate that risk assessment of the potential hazards to health should be carried out.

Monitoring type 2 diabetes from volatile faecal metabolome in Cushing\u2019s syndrome and single Afmid mouse models via a longitudinal study

The analysis of volatile organic compounds (VOCs) as a non-invasive method for disease monitoring, such as type 2 diabetes (T2D) has shown potential over the years although not yet set in clinical practice. Longitudinal studies to date are limited and the understanding of the underlying VOC emission over the age is poorly understood. This study investigated longitudinal changes in VOCs present in faecal headspace in two mouse models of T2D – Cushing’s syndrome and single Afmid knockout mice. Longitudinal changes in bodyweight, blood glucose levels and plasma insulin concentration were also reported. Faecal headspace analysis was carried out using selected ion flow tube mass spectrometry (SIFT-MS) and thermal desorption coupled to gas chromatography-mass spectrometry (TD-GC-MS). Multivariate data analysis of the VOC profile showed differences mainly in acetic acid and butyric acid able to discriminate the groups Afmid and Cushing’s mice. Moreover, multivariate data analysis revealed statistically significant differences in VOCs between Cushing’s mice/wild-type (WT) littermates, mainly short-chain fatty acids (SCFAs), ketones, and alcohols, and longitudinal differences mainly attributed to methanol, ethanol and acetone. Afmid mice did not present statistically significant differences in their volatile faecal metabolome when compared to their respective WT littermates. The findings suggested that mice developed a diabetic phenotype and that the altered VOC profile may imply a related change in gut microbiota, particularly in Cushing’s mice. Furthermore, this study provided major evidence of age-related changes on the volatile profile of diabetic mice.

An in vitro collagen perfusion wound biofilm model; with applications for antimicrobial studies and microbial metabolomics

BackgroundThe majority of in vitro studies of medically relevant biofilms involve the development of biofilm on an inanimate solid surface. However, infection in vivo consists of biofilm growth on, or suspended within, the semi-solid matrix of the tissue, whereby current models do not effectively simulate the nature of the in vivo environment. This paper describes development of an in vitro method for culturing wound associated microorganisms in a system that combines a semi-solid collagen gel matrix with continuous flow of simulated wound fluid. This enables culture of wound associated reproducible steady state biofilms under conditions that more closely simulate the dynamic wound environment. To demonstrate the use of this model the antimicrobial kinetics of ceftazidime, against both mature and developing Pseudomonas aeruginosa biofilms, was assessed. In addition, we have shown the potential application of this model system for investigating microbial metabolomics by employing selected ion flow tube mass spectrometry (SIFT-MS) to monitor ammonia and hydrogen cyanide production by Pseudomonas aeruginosa biofilms in real-time.ResultsThe collagen wound biofilm model facilitates growth of steady-state reproducible Pseudomonas aeruginosa biofilms under wound like conditions. A maximum biofilm density of 1010 cfu slide− 1 was achieved by 30 h of continuous culture and maintained throughout the remainder of the experiment. Treatment with ceftazidime at a clinically relevant dose resulted in a 1.2–1.6 log reduction in biofilm density at 72 h compared to untreated controls. Treatment resulted in loss of complex biofilm architecture and morphological changes to bacterial cells, visualised using confocal microscopy. When monitoring the biofilms using SIFT-MS, ammonia and hydrogen cyanide levels peaked at 12 h at 2273 ppb (±826.4) and 138 ppb (±49.1) respectively and were detectable throughout experimentation.ConclusionsThe collagen wound biofilm model has been developed to facilitate growth of reproducible biofilms under wound-like conditions. We have successfully used this method to: (1) evaluate antimicrobial efficacy and kinetics, clearly demonstrating the development of antimicrobial tolerance in biofilm cultures; (2) characterise volatile metabolite production by P. aeruginosa biofilms, demonstrating the potential use of this method in metabolomics studies.

Factors affecting Alicyclobacillus acidoterrestris growth and guaiacol production and controlling apple juice spoilage by lauric arginate and ϵ-polylysine

Growth of Alicyclobacillus acidoterrestris in fruit juices has been associated with the release of off-odor compounds, such as guaiacol. Guaiacol release was quantified using Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) and method's minimum detection level was 3.6 ppb. The amount of guaiacol released was dependent on the amount of vanillin added to the medium. Sucrose-supplemented yeast starch glucose broth (SS-YSG broth; pH 3.7) and apple juice were spiked with vanillin (10 mg/L), inoculated with A. acidoterrestris and incubated at different temperatures (20°C–45 °C) for up to 528 h. At the temperatures that permitted growth, the bacterium grew slower in apple juice than in SS-YSG broth. Bacterial growth and guaiacol production were prevented in apple juice and inhibited in SS-YSG, when the inoculated products were incubated at 20 °C and 25 °C. When Alicyclobacillus was inoculated in SS-YSG adjusted to pH 2.7–6.7 and incubated at 37 °C, growth of the bacterium and guaiacol production were suppressed at pH 6.7 for up to 354 h and delayed at pH 2.7. Lauric arginate and ϵ-polylysine inactivated Alicyclobacillus cells with no guaiacol production in both SS-YSG and apple juice. However, ϵ-polylysine was more effective than lauric arginate when the SS-YSG (pH 3.7) was inoculated with Alicyclobacillus spores.

High frequency air monitoring by selected ion flow tube-mass spectrometry (SIFT-MS): Influence of the matrix for simultaneous analysis of VOCs, CO2, ozone and water

Selected Ion Flow Tube–Mass Spectrometry (SIFT-MS) with both positive (H3O+, O2•+ and NO+) and negative precursor ions (O•−, OH−, O2•−, NO2−and NO3−) was successfully used for the simultaneous monitoring at the ppbV level of VOCs together with high CO2, water or ozone concentration in complex matrixes. The use of negative precursor ions SIFT-MS allows the detection of carbon dioxide, water and ozone, while increasing the selectivity for VOCs. The complete understanding of all the possible ion-molecule reactions led to the development of accurate quantification methods, independent of any variation of the air matrix composition. For instance, due to the low reactivity of carbon dioxide with OH−, its correct monitoring implies considering not only the reaction of the analyte with the precursor ion, but also with their more reactive hydrates.The results obtained by the developed method were validated on certified standard concentrations. This new SIFT-MS analysis method was further applied to an actual case for the evaluation of indoor air purifying devices and agreed with less convenient and more time-consuming standard analysis methods. It was thus demonstrated for the first time that the simultaneous high frequency, single run and direct monitoring of VOCs, carbon dioxide, water and ozone gave a complete overview of the device operation and of the matrix evolution.

Ozone Quantification by Selected Ion Flow Tube Mass Spectrometry: Influence of Humidity and Manufacturing Gas of Ozone Generator.

The quantification of ozone by SIFT-MS was investigated in conditions suitable with an industrial emission context (high ozone demand, dry air/oxygen as the manufacturing gas of the ozone generator, and high humidity levels beyond saturation at room conditions). Ozone reacts with four negative precursor ions available in the SIFT-MS device (NO2-, O2-, HO-, and O-), each precursor ion having its specific domain of linearity. For a high ozone concentration range, only NO2- and O2- have resulted in a linear behavior (between 1 and 100 ppmv of O3 for NO2-, between 1 and 50 ppmv of O3 for O2-). No water interference was identified during ozone measurements by SIFT-MS using NO2- and O2- precursor ions, even with extreme humidity levels. The presence of nitrogen oxide contaminants (due to the use of dry air as the manufacturing gas of the ozone generator) affected the ozone quantification by SIFT-MS. It is critical for NO2- precursor ions, whose rate constant varied as a function of NO2 concentrations. With O2- precursor ion, ozone was successfully measured in the presence of nitrogen oxides; however, the secondary chemistry must be taken into account.

Real-time differentiation of ethylbenzene and the xylenes using selected ion flow tube mass spectrometry.

Monitoring of isomeric analytes using mass spectrometry usually requires a time-consuming chromatographic separation of the analytes before analysis. Selected ion flow tube mass spectrometry (SIFT-MS) can provide rapid direct analysis of ethylbenzene and xylene by utilizing the different reaction chemistry of the isomers. O2 + yields the same product ions from each isomer but in different ratios. OH- yields different product ions. The reaction chemistry of C8 H10 with the reagent ion OH- generated from a microwave discharge of moist air in a commercial SIFT-MS instrument was utilized in this study. The product ion from OH- yielded ions at different masses for each isomer. To gain an understanding of how the product ion from ethylbenzene of HO2 - was generated, a theoretical study of the potential reaction surface was undertaken that accounted for the experimental observations. Measurements of OH- with ethylbenzene showed the product ion to be HO2 - at m/z 33. The reaction of OH- with xylene yielded the major product ion at m/z 105, C8 H9 - . HO2 - also underwent a slow secondary reaction with CO2 and O2 present from air in the samples. These findings were supported by calculations of the potential energy surface for the reactions. Measurements made on a certified gas mixture of ethylbenzene and xylene in the concentration range up to 5000 ppbv gave a linear response for each analyte. A fast, efficient method was developed for monitoring xylene and ethylbenzene in a mixture without the need for chromatographic separation before analysis using SIFT-MS.

Direct analysis of aldehydes and carboxylic acids in the gas phase by negative ionization selected ion flow tube mass spectrometry: Quantification and modelling of ion-molecule reactions.

The concentrations of aldehydes and volatile fatty acids have to be controlled because of their potential harmfulness in indoor air or relationship with the organoleptic properties of agri-food products. Although several specific analytical methods are currently used, the simultaneous analysis of these compounds in a complex matrix remains a challenge. The combination of positive and negative ionization selected ion flow tube mass spectrometry (SIFT-MS) allows the accurate, sensitive and high-frequency analysis of complex gas mixtures of these compounds. The ion-molecule reactions of negative precursor ions (OH- , O•- , O2 •- , NO2 - and NO3 - ) with five aldehydes and four carboxylic acids were investigated in order to provide product ions and rate constants for the quantification of these compounds by negative ion SIFT-MS. The results were compared with those obtained by conventional analysis methods and/or with already implemented SIFT-MS positive ionization methods. The modelling of hydroxide ion (OH- )/molecule reaction paths by ab-initio calculation allowed a better understanding of these gas-phase reactions. Deprotonation systematically occurs by reaction between negative ions and aldehydes or acids, leading to the formation of [M - H]- primary ions. Ab-initio calculations demonstrated the α-CH deprotonation of aldehydes and the acidic proton abstraction for fatty acids. For aldehydes, the presence of water in the flow tube leads to the formation of hydrated ions, [M - H]- .H2 O. With the NO2 - precursor ion, a second reaction channel results in ion-molecule association with the formation of M.NO2 - ions. Except for formaldehyde, all the studied compounds can be quantified by negative ion SIFT-MS with significant rate constants. In addition to positive ion SIFT-MS with H3 O+ , O2 + and NO+ precursor ions, negative ionization with O•- , O2 •- , OH- , NO2 - and NO3 - extends the range of analysis of aldehydes and carboxylic acids in air without a preparation or separation step. This methodology was illustrated by the simultaneous quantification in single-scan experiments of seven aldehydes and six carboxylic acids released by building materials.

Feasibility of perioperative volatile organic compound breath testing for prediction of paralytic ileus following laparoscopic colorectal resection.

Despite implementation of enhanced recovery after surgery (ERAS) and laparoscopic techniques, postoperative ileus (POI) remains frequent after colorectal surgery, impacting the patient, their recovery and health-care resources. Presently there are no tests that reliably predict or enable early POI diagnosis. Volatile organic compounds (VC) are products of human and microbiota cellular metabolism and we hypothesised that a detectable alteration occurs in POI. This was a prospective observational study of patients undergoing laparoscopic colorectal resection within an established ERAS programme. Standardized end-expiratory breath sampling was performed on the morning of surgery and on the first three postoperative mornings. The concentrations of VCs commonly found in intestinal gas were analysed using selected ion flow tube mass spectrometry and GastroCH4 ECK®. Feasibility data, bowel preparation, postoperative oral intake, POI and 30-day morbidity were recorded. Of the 75 potentially eligible patients, 58 (77%) agreed to participate. Per-protocol breath sampling was successfully completed in 94%. There were no analytical failures. Baseline and postoperative concentrations of VCs were broadly comparable and were not altered by bowel preparation or postoperative oral intake. POI developed in 14 (29%) patients. Preoperative ammonia concentration was higher in patients who developed POI [830parts per billion (ppb) vs 510ppb, P=0.027]. There was an increase in the concentration of acetic acid detected on day 2 in patients who developed POI (99ppb vs 171ppb, P=0.021). Repeated VC breath sampling and analysis is feasible in the perioperative setting. An elevated ammonia concentration on the morning of surgery may be a potential predictor of POI.

Addition of fast gas chromatography to selected ion flow tube mass spectrometry for analysis of individual monoterpenes in mixtures

Abstract. Soft chemical ionization mass spectrometry (SCI-MS) techniques can be used to accurately quantify volatile organic compounds (VOCs) in air in real time; however, differentiation of isomers still represents a challenge. A suitable pre-separation technique is thus needed, ideally capable of analyses over a few tens of seconds. To this end, a bespoke fast gas chromatography (GC) instrument with an electrically heated 5 m long metallic capillary column was coupled to selected ion flow tube mass spectrometry (SIFT-MS) measurements. To assess the performance of this combination, a case study of monoterpene isomer (C10H16) analyses was carried out. The monoterpenes were quantified by SIFT-MS using H3O+ reagent ions (analyte ions C10H17+, m∕z 137, and C6H9+, m∕z 81) and NO+ reagent ions (analyte ions C10H16+, m∕z 136, and C7H9+, m∕z 93). The combinations of the fragment ion relative intensities obtained using H3O+ and NO+ were shown to be characteristic of the individual monoterpenes. Two non-polar GC columns (Restek Inc.) were tested: the advantage of MXT-1 was shorter retention, whilst the advantage of MXT-Volatiles was better separation. Thus, it is possible to identify components of a monoterpene mixture in less than 45 s using the MXT-1 column and to separate them in less than 180 s using the MXT-Volatiles column. Quality of the separation and the sensitivity of present technique (limit of detection, LOD, ∼16 ppbv) was found to be inferior compared to commercially available fast GC solutions coupled with proton transfer reaction mass spectrometry (PTR-MS, LOD ∼1 ppbv) due to the limited sample flow through the column. However, using combinations of two reagent ions improved identification of monoterpenes not well resolved by the chromatograms. As an illustrative example, the headspace of needle samples of three conifer species was analysed by both reagent ions and with both columns showing that mainly α-pinene, β-pinene and 3-carene were present. The system can thus be used for direct rapid monitoring of monoterpenes above 20 ppbv, such as applications in laboratory studies of monoterpene standards and leaf headspace analysis. Limitation of the sensitivity due to the total sample flow can be improved using a multi-column pre-separation.

SIFT-ing archaeological artifacts: Selected ion flow tube-mass spectrometry as a new tool in archaeometry

A fast non‐destructive approach based on the use of portable selected ion flow tube-mass spectrometry (SIFT-MS) was used for the first time to characterize organic materials in archaeological artifacts. The high sensitivity, specificity and selectivity SIFT soft chemical ionization mass spectrometry enabled us to investigate the composition of organic residues collected from ancient Egyptian findings in order to demonstrate the robustness of the techniques with different matrices. In addition, we tested SIFT-MS directly on an archaeological Egyptian amphora to prove its suitability as a completely non-invasive technique.Parallel investigations on all the samples were performed by GC/MS analysis to correlate and confirm the data obtained by SIFT-MS.The possibility of using a portable mass spectrometer on an excavation site or in a museum would be a significant step forward in the non-invasive analysis of organic archaeological materials, enabling archeologists and conservators to obtain real-time information on the molecular composition of organic residues.

Validation Study of Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) in Heritage Science: Characterization of Natural and Synthetic Paint Varnishes by Portable Mass Spectrometry.

The identification at molecular level of organic materials in heritage objects as paintings requires in most cases the collection of micro-samples followed by micro-destructive analysis. In this study, we explore the possibility to characterize natural and synthetic resins used as paint varnishes by mean of non-invasive analysis of released volatile organic compounds (VOCs) through selected ion flow tube-mass spectrometry (SIFT-MS). SIFT-MS is a portable direct mass spectrometric technique that achieves the analysis of VOCs at trace levels in real time, by controlled ultra-soft chemical ionization using eight different chemical ionization agents. We tested the portable instrumentation on different reference resins used as paint varnishes, both natural (mastic, dammar, and colophony) and synthetic (Paraloid B67, MS2A, Regalrez 1094, and polyvinyl acetate), to evaluate the possibility to acquire qualitative data for the identification of these materials in heritage objects avoiding any sampling. This new analytical approach was validated by comparison with the traditional approach for VOCs analysis based on solid phase micro extraction-gas chromatography/mass spectrometry (SPME-GC/MS) analysis. The results demonstrate the use of SIFT-MS as an in situ non-invasive and non-destructive mass spectrometric technique to identify organic materials, such as paint varnishes.

Assessment of an experimental method for determining the three key parameters of VOC emissions from solid materials

The VOC emission processes from a solid material can be described by three key parameters: the partition coefficient (K), the initial emittable concentration (C0) and, the diffusion coefficient (D). These emission key parameters need to be determined experimentally for a VOC-material pair. A new method from literature allows determining simultaneously the three emission key parameters. However, this method has been evaluated in a single experiment only for formaldehyde. Therefore, the purpose of this study is to assess the efficiency and the reproducibility of the experimental method from literature performing three tests in the same experimental conditions. This work permits to determine the three key parameters of eight main VOC emitted from a particleboard and to evaluate the accuracy of the experimental method. Successfully, experiments carried out using a 128 L well-mixed chamber containing a particleboard, and connected to an online gas analyzer (Selected Ion Flow Tube-Mass Spectrometry), allow the effective characterization of the source material. Results evidence that compared to other VOCs, formaldehyde shows a specific behaviour: the response of formaldehyde between airtight and ventilated regimes is highly contrasted with those of other emitted VOCs.

Determining modified reaction parameters for the real-time measurement of BTEX in biogas and nitrogen using Selected Ion Flow Tube Mass Spectrometry (SIFT-MS)

The increasing demand for high-quality biogas and the reduction of reliance on natural gas have driven the need for a well-defined framework to ensure conformity and quality of biogas by the introduction of traceable reference materials and methods across the community. Furthermore, there is a great need to quantify critical trace impurities in biogas. Here, we perform real-time measurements on reference gas standards containing trace hydrocarbons in biogas that are traceable to the international system of units using Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). There are limited data on reaction rate constants in biogas matrices for SIFT-MS, and here we use the traceable gas standards to determine and compare the reaction rate constants of trace hydrocarbons in biogas and nitrogen. Here, we modify SIFT-MS constants for biogas avoiding the current 30 % bias and prevent the overestimation in the concentration of hydrocarbon amount fractions.

Comprehensive odorant analysis for on‐line applications using selected ion flow tube mass spectrometry (SIFT‐MS)

AbstractSelected ion flow tube mass spectrometry (SIFT‐MS) is a direct mass spectrometry technique developed for volatile organic compound (VOC) analysis. In this comprehensive review of the SIFT‐MS flavour literature, its flexibility and utility are evident. SIFT‐MS has found wide application in the analysis of formation and release of odorants in fruits, vegetables, nuts, and seeds – including flavour and sensory optimization during cooking. Dairy products and poultry, red meat, and seafood also comprise a significant number of studies across processing, sensory, and shelf‐life studies. Edible oils, initially investigated for flavour and oxidative status, have recently been very successfully classified according to origin using a combined chemometrics and SIFT‐MS approach. Other recent developments – across different food groups – have been growth in applications to packaging (including meats in modified atmosphere packaging), and correlations of SIFT‐MS data with various types of sensory testing. The continuing growth of food odorant publications indicates that the SIFT‐MS technique has a significant role to play in understanding and managing favourable and unfavourable aroma formation in both academia and industry.

The Use of Selected Ion Flow Tube-Mass Spectrometry Technology to Identify Breath Volatile Organic Compounds for the Detection of Head and Neck Squamous Cell Carcinoma: A Pilot Study.

Background: Head and neck squamous cell carcinoma (HNSCC) is the sixth most common form of cancer worldwide, with approximately 630,000 new cases diagnosed each year. The development of low-cost and non-invasive tools for the detection of HNSCC using volatile organic compounds (VOCs) in the breath could potentially improve patient care. The aim of this study was to investigate the feasibility of selected ion flow tube mass spectrometry (SIFT-MS) technology to identify breath VOCs for the detection of HNSCC. Materials and Methods: Breath samples were obtained from HNSCC patients (N = 23) and healthy volunteers (N = 21). Exhaled alveolar breath samples were collected into FlexFoil® PLUS (SKC Limited, Dorset, UK) sampling bags from newly diagnosed, histologically confirmed, untreated patients with HNSCC and from non-cancer participants. Breath samples were analyzed by Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) (Syft Technologies, Christchurch, New Zealand) using Selective Ion Mode (SIM) scans that probed for 91 specific VOCs that had been previously reported as breath biomarkers of HNSCC and other malignancies. Results: Of the 91 compounds analyzed, the median concentration of hydrogen cyanide (HCN) was significantly higher in the HNSCC group (2.5 ppb, 1.6–4.4) compared to the non-cancer group (1.1 ppb, 0.9–1.3; Benjamini–Hochberg adjusted p < 0.05). A receiver operating curve (ROC) analysis showed an area under the curve (AUC) of 0.801 (95% CI, 0.65952–0.94296), suggesting moderate accuracy of HCN in distinguishing HNSCC from non-cancer individuals. There were no statistically significant differences in the concentrations of the other compounds of interest that were analyzed. Conclusions: This pilot study demonstrated the feasibility of SIFT-MS technology to identify VOCs for the detection of HNSCC.

The application of selected ion flow tube-mass spectrometry to follow volatile formation in modified-atmosphere-packaged cooked ham.

Cooked pork products, i.e., sliced cooked hams maintained under modified-atmosphere-packaging (MAP), were analysed both microbiologically and with respect to volatile levels during storage. Three storage temperature ranges were compared (4-6 °C, 7-9 °C, and 11-13 °C), representing different refrigeration conditions at household level. The microbial loads were determined by plating samples on six different agar media, followed by (GTG)5-PCR fingerprinting of genomic DNA of selected isolates, and identification of representative isolates by 16S rRNA, pheS, and rpoA gene sequencing. Carnobacterium maltaromaticum, Lactobacillus sakei, and Serratia proteamaculans were the major bacterial species found among the 619 isolates identified. The volatiles produced during storage were followed by selected ion flow tube-mass spectrometry (SIFT-MS) and the identity of the volatiles was confirmed by headspace solid-phase microextraction combined with gas chromatography and time-of-flight mass spectrometry (HS-SPME-GC-TOF-MS). SIFT-MS analysis showed that volatiles, such as 2,3-butanediol, acetoin, and ethanol, may serve as potential markers for spoilage development. Differences in volatile production between samples were likely due to discrepancies in the initial microbial load and the effect of storage conditions. In conclusion, this study combines the use of new mass spectrometric techniques to examine volatile production during spoilage as an additional source of information during microbiological community analysis.