Combining Thermal Desorption with Selected Ion Flow Tube Mass Spectrometry for Analyses of Breath Volatile Organic Compounds.

An instrument integrating thermal desorption (TD) to selected ion flow tube mass spectrometry (SIFT-MS) is presented, and its application to analyze volatile organic compounds (VOCs) in human breath is demonstrated for the first time. The rationale behind this development is the need to analyze breath samples in large-scale multicenter clinical projects involving thousands of patients recruited in different hospitals. Following adapted guidelines for validating analytical techniques, we developed and validated a targeted analytical method for 21 compounds of diverse chemical class, chosen for their clinical and biological relevance. Validation has been carried out by two independent laboratories, using calibration standards and real breath samples from healthy volunteers. The merging of SIFT-MS and TD integrates the rapid analytical capabilities of SIFT-MS with the capacity to collect breath samples across multiple hospitals. Thanks to these features, the novel instrument has the potential to be easily employed in clinical practice.

Recent developments and applications of selected ion flow tube mass spectrometry (SIFT-MS).

Selected ion flow tube mass spectrometry (SIFT-MS) is now recognized as the most versatile analytical technique for the identification and quantification of trace gases down to the parts-per-trillion by volume, pptv, range. This statement is supported by the wide reach of its applications, from real-time analysis, obviating sample collection of very humid exhaled breath, to its adoption in industrial scenarios for air quality monitoring. This review touches on the recent extensions to the underpinning ion chemistry kinetics library and the alternative challenge of using nitrogen carrier gas instead of helium. The addition of reagent anions in the Voice200 series of SIFT-MS instruments has enhanced the analytical capability, thus allowing analyses of volatile trace compounds in humid air that cannot be analyzed using reagent cations alone, as clarified by outlining the anion chemistry involved. Case studies are reviewed of breath analysis and bacterial culture volatile organic compound (VOC), emissions, environmental applications such as air, water, and soil analysis, workplace safety such as transport container fumigants, airborne contamination in semiconductor fabrication, food flavor and spoilage, drugs contamination and VOC emissions from packaging to demonstrate the stated qualities and uniqueness of the new generation SIFT-MS instrumentation. Finally, some advancements that can be made to improve the analytical capability and reach of SIFT-MS are mentioned.

Untargeted selected ion flow tube mass spectrometry headspace analysis: High-throughput differentiation of virgin and recycled polyethylene pellets.

RATIONALE: Recycled plastics are increasingly used for packaging of fast-moving consumer goods (FMCG). Compared with packaging made from virgin polymers, there is greater risk of taints entering products due to prior use of the polymers and incomplete cleaning. Increased quality assurance testing of polymer feedstock is required for recycled packaging. Selected ion flow tube mass spectrometry (SIFT-MS) analysis coupled with multivariate statistical data processing can provide high-throughput untargeted screening of recycled polymers at low cost per sample. METHODS: SIFT-MS is a direct-injection MS technique that provides high-throughput automated headspace analysis of polymer samples when coupled with a syringe-injection autosampler (12 incubated samples per hour). Full-scan SIFT-MS data were processed using multivariate statistical analysis (specifically, the soft independent modeling by class analogy (SIMCA) algorithm). RESULTS: SIFT-MS full-scan data were acquired for ten replicates each of ten recycled and four virgin high-density polyethylene (HDPE) pellet products from multiple manufacturers. The samples varied approximately 20-fold in terms of total volatile residue, while showing very high repeatability across replicates. SIFT-MS scan data were dominated by aliphatic and monoterpene hydrocarbon residues, and - to a lesser extent - alcohols. Application of the SIMCA algorithm to the data resulted in successful classification by both individual samples and manufacturers. CONCLUSIONS: Automated, untargeted SIFT-MS analysis coupled with multivariate statistical data analysis has the potential to provide rapid, effective screening of recycled polymer products, which would provide increased quality assurance of recycled polymers used for FMCG.

Standard Validation Protocol for Selected Ion Flow Tube Mass Spectrometry Methods Applied to Direct Headspace Analysis of Aqueous Volatile Organic Compounds.

Analysis of volatile organic compounds (VOCs) in water is conventionally conducted using gas chromatography (GC)-based methods, for which sample preparation demands are relatively high and throughput is relatively low due to the time taken to achieve chromatographic separation. Direct mass spectrometry (DMS) techniques such as selected ion flow tube mass spectrometry (SIFT-MS) have potential to analyze water headspace (HS) at high sensitivity with minimal sample preparation, eliminating preconcentration/purging and/or water management steps. However, the dearth of guidance for validation of DMS methods is an impediment to their adoption in routine analysis. This study applies and adapts an internationally recognized pharmaceutical industry guidance document for method validation to a prototypical SIFT-MS headspace analysis method for 17 toxic VOCs in water. The approach to validation is, however, applicable to any routine analysis conducted using SIFT-MS, and very likely to any methods developed using other DMS techniques. For the method developed and validated here, linearities (as measured by the linear regression coefficient, R2) were better than 0.990 for all compounds. Repeatability (measured using relative standard deviation, RSD) was less than 10% for all compounds. Similar method performance was observed for accuracy and recovery. The performance criteria achieved by this HS-SIFT-MS method suggest it has potential application in environmental and pharmaceutical routine analyses, perhaps as a rapid screening tool.

Language of Uncertainty: the Expression of Decisional Conflict Related to Skin Cancer Prevention Recommendations.

User-generated information on the Internet provides opportunities for the monitoring of health information consumer attitudes. For example, information about cancer prevention may cause decisional conflict. Yet posts and conversations shared by health information consumers online are often not readily actionable for interpretation and decision-making due to their unstandardized format. This study extends prior research on the use of natural language as a predictor of consumer attitudes and provides a link to decision-making by evaluating the predictive role of uncertainty indicators expressed in natural language. Analyzed data included free-text comments and structured scale responses related to information about skin cancer prevention options. The study identified natural language indicators of uncertainty and showed that it can serve as a predictor of decisional conflict. The natural indicators of uncertainty reported here can facilitate the monitoring of health consumer perceptions about cancer prevention recommendations and inform education and communication campaign planning and evaluation.

The Hawlix: a simple and aesthetic prosthetic- orthodontic retainer.

This report introduces the Hawlix, a hybrid thermoformed and cold-cured retainer. It was developed to overcome the limitations that modified Hawley retainers possess when used in patients with bounded saddles, attributable to dental trauma or hypodontia. The Hawlix can be used as an intermediate retainer while a patient is waiting to receive restorative treatment. Some of the advantages of the Hawlix over the modified Hawley retainer include: superior aesthetics, cost-effectiveness, ease of manufacture, adequate resistance to fracture, preservation of a residual ridge, and precise space maintenance.

Rapid monitoring of volatile organic compounds: a comparison between gas chromatography/mass spectrometry and selected ion flow tube mass spectrometry.

RATIONALE: The gold standard for monitoring volatile organic compounds (VOCs) is gas chromatography/mass spectrometry (GC/MS). However, in many situations, when VOC concentrations are at the ppmv level, there are complicating factors for GC/MS. Selected ion flow tube mass spectrometry (SIFT-MS) is an emerging technique for monitoring VOCs in air. It is simpler to use and provides results in real time. METHODS: Three different experiments were used for the comparison. First SIFT-MS was applied to monitor the concentrations of 25 VOCs in a mixture at concentrations up to 1 ppmv using only a generic database for known kinetic data of three reagent ions (H3O(+), NO(+) and O2(+)) with each VOC. In experiment 2, a side-by-side comparison was made of 17 VOCs at concentrations between 1 ppmv and 5 ppbv after small corrections had been made to the SIFT-MS kinetic data. In a third experiment, a side-by-side comparison examined two groups of samples received for commercial analysis. RESULTS: In experiment 1, 85% of the VOC concentrations were within 35% of their stated values without any calibration of the SIFT-MS instrument. In experiment 2, the two techniques yielded good correspondence between the measured VOC concentrations. In experiment 3, good correlation was found for VOCs from three of the samples. However, interferences from some product ions gave over-reported values in one sample from the SIFT-MS instrument. CONCLUSIONS: These three experiments showed that GC/MS was better suited to monitoring samples containing large numbers of VOCs at high concentrations. In all other applications, SIFT-MS proved simpler to use, was linear with concentration over a much wider concentration range than GC/MS and provided faster results.

Selected ion flow tube studies of several siloxanes.

RATIONALE: People are using increasing amounts of siloxanes that ultimately end up in landfills and then in landfill gas and biogas digesters. Their presence poses difficulties for industries seeking to utilize the energy content of landfill and biogas, as the combustion process oxidises silicon to silicon dioxide that in turn damages engine parts. Rapid, efficient and accurate methods are needed to quantify their presence. METHODS: Selected ion flow tube mass spectrometry (SIFTMS) is an emerging real-time technique that has found application for monitoring trace volatiles in air. Samples containing the trace volatiles are simply drawn into the flow tube and convected in a stream of helium. Chemical ionization reactions from mass-selected reagent ions with the volatiles ensue. To quantify the volatiles in the sample, the ion chemistry of the reagent ion with each volatile must be known. RESULTS: Rate coefficients and product ion branching ratios were found for the compounds dodecamethylpentasiloxane, decamethylcyclopentasiloxane, decamethyltetrasiloxane, octamethylcyclotetrasiloxane, triethylsilanol, tetramethylsilane and hexamethyldisilazane. CONCLUSIONS: The ion-molecule reactions of the seven silicon-containing compounds examined here were fast, occurring at or near the collision rate, thus allowing for detection at low levels. The very simple reaction chemistry found of proton transfer, electron transfer and methyl loss will enable easy quantitation of the siloxanes in landfill gas and biogas using the SIFTMS technique.

Patient education videos for elective colorectal surgery: results of a randomized controlled trial.

AIM: Recent advances in surgery have focused on peri-operative care and interventions to improve outcome following surgery. Psychological preparation has a positive impact on recovery and incorporates a range of strategies with dissemination of information as one of the key elements. Information can be given verbally, through printed information or through use of a video. Traditionally, reliance has been on the use of written material as an adjunct to patient education in clinic. The current study is a randomized trial on the use of video education in patients undergoing elective colorectal resection within an enhanced recovery programme. METHOD: Sixty-five eligible patients undergoing elective colorectal surgery were identified and 61 were randomized between August 2010 and August 2011 to either video and information leaflets or information leaflets alone. A fast track protocol was established for all the patients. Clinicians in charge of postoperative recovery were blinded. Standard discharge criteria were employed for all patients. RESULTS: Of 61 patients randomized, one dropped out and outcomes on 60 were analysed. There was no difference in baseline characteristics between the groups (age, P = 0.964; body mass index, P = 0.829). Twenty-eight (91%) patients in the video group had left sided resections while two (6%) had right sided resections. Nineteen (66%) in the non-video group had left sided resections while nine (31%) had right sided resections. One (3%) patient in the non-video group and one (3%) in the video group had a total colectomy. Fourteen (45%) patients in the video group and 12 (41%) in the non-video group had surgery completed laparoscopically. There was no difference in the primary (median hospital stay 5 vs 5 days; P = 0.239) or the secondary outcome measures (pain score on movement, P = 0.338; pain score at rest, P = 0.989; nausea score, P = 0.74; epidural use, P = 0.984; paracetamol use, P = 0.44; voltarol use, P = 0.506) between the groups. CONCLUSION: Use of video education in the psychological preparation of patients undergoing elective colorectal surgery does not improve short-term outcomes.

Robust Automated SIFT-MS Quantitation of Volatile Compounds in Air Using a Multicomponent Gas Standard.

Selected ion flow tube mass spectrometry, SIFT-MS, has been widely used in industry and research since its introduction in the mid-1990s. Previously described quantitation methods have been advanced to include a gas standard for a more robust and repeatable analytical performance. The details of this approach to calculate the concentrations from ion-molecule reaction kinetics based on reaction times and instrument calibration functions determined from known concentrations in the standard mix are discussed. Important practical issues such as the overlap of product ions are outlined, and best-practice approaches are presented to enable them to be addressed during method development. This review provides a fundamental basis for a plethora of studies in broad application areas that are possible with SIFT-MS instruments.

Accurate selected ion flow tube mass spectrometry quantification of ethylene oxide contamination in the presence of acetaldehyde.

In September 2020, traces of ethylene oxide (a toxic substance used as a pesticide in developing countries but banned for use on food items within the European Union) were found in foodstuffs containing ingredients derived from imported sesame seed products. Vast numbers of foodstuffs were recalled across Europe due to this contamination, leading to expensive market losses and extensive trace exposure of ethylene oxide to consumers. Therefore, a rapid analysis method is needed to ensure food safety by high-throughput screening for ethylene oxide contamination. Selected ion flow tube mass spectrometry (SIFT-MS) is a suitable method for rapid quantification of trace amounts of vapours in the headspace of food samples. It turns out, however, that the presence of acetaldehyde complicates SIFT-MS analyses of its isomer ethylene oxide. It was proposed that a combination of the H3O+ and NO+ reagent ions can be used to analyse ethylene oxide in the presence of acetaldehyde. This method is, however, not robust because of the product ion overlaps and potential interferences from other matrix species. Thus, we studied the kinetics of the reactions of the H3O+, NO+, OH- and O-˙ ions with these two compounds and obtained their rate coefficients and product ion branching ratios. Interpretation of these experimental data revealed that the OH- anions are the most suitable SIFT-MS reagents because the product ions of their reactions with acetaldehyde (CH2CHO- at m/z 43) and ethylene oxide (C2H3O2- at m/z 59) do not overlap.

An origin for short gamma-ray bursts unassociated with current star formation.

Two short (< 2 s) gamma-ray bursts (GRBs) have recently been localized and fading afterglow counterparts detected. The combination of these two results left unclear the nature of the host galaxies of the bursts, because one was a star-forming dwarf, while the other was probably an elliptical galaxy. Here we report the X-ray localization of a short burst (GRB 050724) with unusual gamma-ray and X-ray properties. The X-ray afterglow lies off the centre of an elliptical galaxy at a redshift of z = 0.258 (ref. 5), coincident with the position determined by ground-based optical and radio observations. The low level of star formation typical for elliptical galaxies makes it unlikely that the burst originated in a supernova explosion. A supernova origin was also ruled out for GRB 050709 (refs 3, 31), even though that burst took place in a galaxy with current star formation. The isotropic energy for the short bursts is 2-3 orders of magnitude lower than that for the long bursts. Our results therefore suggest that an alternative source of bursts--the coalescence of binary systems of neutron stars or a neutron star-black hole pair--are the progenitors of short bursts.

Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) as an Alternative to Gas Chromatography/Mass Spectrometry (GC/MS) for the Analysis of Cyclohexanone and Cyclohexanol in Plasma.

Self-poisoning with professional agricultural pesticide products is responsible for about 20% of global suicide, with most cases occurring in South Asia and China. Treatment of severe poisoning involves long-term intensive clinical care and is often unsuccessful. Solvent co-formulants (such as cyclohexanone) also contribute to mortality themselves or via more toxic metabolic products (such as cyclohexanol). Faster detection of co-formulants could aid earlier identification of pesticide poisoning and faster intervention, reducing mortality. Conventional analysis of volatiles in blood uses headspace (HS)-GC/MS. This paper evaluates SIFT-MS, a direct MS technique that provides higher sample throughput than GC/MS, as a potential tool for cyclohexanone and cyclohexanol analysis in plasma. Both instruments were calibrated using a conventional approach prior to analysis of each porcine plasma sample on both instruments. Comparative data were evaluated using Bland-Altman plots, demonstrating that the techniques were in good agreement. Compared with GC/MS, SIFT-MS provides fourfold higher sample throughput and shows great promise as an alternative analytical tool.

Molecular biodiversity and population structure in common ash (Fraxinus excelsior L.) in Britain: implications for conservation.

Current forestry policy promotes the use of local seed for new plantings, on the assumption that local material may be better adapted to local conditions. However, landscape-scale genetic studies which are necessary to underpin conservation and breeding strategies are often lacking. We investigated molecular diversity in common ash (Fraxinus excelsior L.) sampled from 42 British and six French sites with microsatellites. Chloroplast haplotype H04 was the most common and widespread in Britain, although rare and localized individuals with H02 and H09 were also detected. In addition, three new chloroplast haplotypes were identified, and these were rare and highly localized. In terms of nuclear microsatellite markers, allelic richness differed between sites and decreased in an east to west direction. Differentiation between sites was often very low (mean F(ST) 0.025), indicating few differences between the majority of sites. There was a clear excess of homozygotes (mean H(O) 0.669, mean H(E) 0.818) and a relatively high F(IS) (mean 0.182), suggests a consistent level of inbreeding or a widespread Wahlund effect in many F. excelsior sites. Gene pool ancestry analysis suggested that the majority of British F. excelsior belongs to a single meta-population which covers mainland western and central Europe. Three northern and western sites diverged markedly from the dominant population, and may represent remnants of two late potential Ice Age refugia in northern Britain. The data provide new information which will aid development of appropriate conservation policies for ash and other wind pollinated tree species.

Real-time measurement of peroxyacetyl nitrate using selected ion flow tube mass spectrometry.

The on-line detection of gaseous peroxyacetyl nitrate (PAN) using selected ion flow tube mass spectrometry (SIFT-MS) has been investigated using a synthetic sample of PAN in air at a humidity of approximately 30%. Using the H(3)O(+) reagent ion, signals due to PAN at m/z 122, 77 and 95 have been identified. These correspond to protonated PAN, protonated peractetic acid and its water cluster, respectively. These products and their energetics have been probed through quantum mechanical calculations. The rate coefficient of H(3)O(+) has been estimated to be 4.5 x 10(-9) cm(3) s(-1), leading to a PAN sensitivity of 138 cps/ppbv. This gives a limit of detection of 20 pptv in 10 s using the [M+H](+) ion of PAN at m/z 122.

Monitoring chloramines and bromamines in a humid environment using selected ion flow tube mass spectrometry.

The selectivity and sensitivity of selected ion flow tube mass spectrometry (SIFT-MS) for individual breath analysis of haloamines has been improved by heating the flow tube in a commercial instrument to around 106 degrees C. Data is presented showing the marked reduction in the number density of water clusters of product ions of common breath metabolites that are isobaric with the product ions from monochloramine and monobromamine that are used to monitor the haloamine concentrations. These results have direct relevance to the real-time monitoring of chloramines in drinking water, swimming pools and food processing plants. However, once the isobaric overlaps from water cluster ions are reduced at the higher temperatures, there is no conclusive evidence showing the presence of haloamines on single breath exhalations in the mid parts per trillion range from examination of the breaths of volunteers.

An alternative retainer design for cleft patients: the "aesthetic" retainer.

The objective of this report is to describe an original retainer design for retention following orthodontic treatment in cleft lip and palate patients in order to improve the aesthetics of anterior maxillary dentoalveolar cleft defects. The technique incorporates features of both traditional and modern retainer design. The advantages of the technique and fabrication process are described.

Real-time monitoring of hazardous air pollutants.

Selected ion flow tube mass spectrometry (SIFT-MS) is a technique that offers real-time alternatives to existing methods for monitoring hazardous air pollutants (HAPs) in the environment using chemical ionization. The use of this technique requires knowledge of the kinetic parameters of the reagent ions H(3)O(+), NO(+), and O(2)(+) that are most commonly used. We report here measurements with these reagent ions of kinetic parameters for 17 HAP molecules ranging from 1,1-dichloroethene to nitrobenzene. From these data, limits of quantitation are established for all 17 compounds on a commercial SIFT-MS instrument and are found to be well below the time-weighted averages required by legislating bodies for workplace conditions.