Concentrations Of Methyl Mercaptan Research Articles

How far does feedback on oral malodor assessment influence the decision to quit smoking?

A retrospective, uncontrolled, questionnaire-based, pre-post study involving adult male smoker volunteers who were invited to attend a one-day smoking cessation event at their workplace. To assess the effect of feedback on motivation for smoking cessation using oral-malodor measurements. At baseline, the participants attended a brief video presentation regarding various oral health-specific effects of smoking, joined a group introduction to smoking-cessation aids, and were given questionnaires that inquired information about smoking status including type, daily consumption, and duration. Subsequently, respiratory function and oral-malodor assessment were conducted using exhaled and oral cavity air, respectively. To measure oral-malodor, hydrogen sulfide, methyl mercaptan, and dimethyl sulfide concentrations were determined. Participants' intention for smoking cessation was evaluated through questionnaire before and after the event, classifying their intentions as aiming to quit within the next month, within the next 6 months, or having no intention to quit smoking. Immediate feedback on respiratory function and oral malodor measurements was provided by medical and dental blinded examiners, respectively. A total of 241 men, aged 20-54 years, were enrolled and included:169 (70.1%) exclusive cigarette smokers, 39 (16.2%) exclusive heated-tobacco product users, and 33 (13.7%) users of both. Prior to the health event, 8.7%, 17.0%, and 74.3% of smokers expressed intentions to quit within the next month, the next 6 months, or had no intention to quit, respectively. After the event, the corresponding percentages shifted to 17.8%, 26.6%, and 55.6%. In multivariable logistic regression analysis, the association with intention to quit in the next month was significant only for methyl mercaptan concentration in oral cavity air, with an adjusted odds ratio (AOR) of 4.24 (95% CI: 1.52-11.84; p = 0.006). Sensitivity analysis revealed that this association was concentration-dependent. On the other hand, higher daily tobacco consumption (≥ 15 pieces) was significantly associated with less likely intention to quit in the next 6 months (AOR = 0.37; 95% CI: 0.15-0.92, p = 0.032). Feedback on oral malodor measurement may support the motivation of men to quit smoking within the next month, rather than waiting for the next 6 months.

Oral-malodor measurement and intention to quit smoking in men: A before-after study.

Few studies have examined the effect of feedback based on oral-malodor measurements on the motivation to quit smoking. Therefore, this study examined whether oral-malodor measurements were associated with the intention to quit smoking. This retrospective, uncontrolled before-after study invited smokers to a workplace health event in 2019 and 2020 to motivate them to quit smoking. They attended seminars on oral health and smoking cessation aids, and then underwent respiratory function and oral-malodor measurements using exhaled and oral cavity air, respectively. Intention to quit smoking was evaluated by answers to questions regarding the intention to quit in the next 1 or 6 months in questionnaires collected before and after the event. This study analyzed 241 men aged 20-54 years (mean: 33.2 ± 10.5) to examine factors associated with the intention to quit in multivariable logistic regression analyses for age, tobacco type (cigarettes and heated-tobacco products), and category of tobacco consumption. Before the event, 8.7%, 17.0%, and 74.3% of smokers had intended to quit in the next month, the next six months, or had no intention to quit, respectively. After the event, the respective percentages were 17.8%, 26.6%, and 55.6%. A higher methyl mercaptan concentration, a volatile sulfide component of oral malodor, was significantly associated with the intention to quit in the next month (adjusted odds ratio, AOR=4.24; 95% CI: 1.52-11.8, p=0.006). The participants with higher daily tobacco consumption were less likely to acquire the intention to quit in the next six months (AOR=0.37; 95% CI: 0.15-0.92, p=0.032). Other variables, such as lung age deficit, exhaled CO concentration, and hydrogen sulfide concentration (another component of oral malodor), were not significantly associated. Oral-malodor measurement feedback may help motivate men to quit smoking in the next 1 month rather than in the next six months.

Study on adsorption of low-concentration methyl mercaptan by starch-based activated carbon.

The development of a low-concentration methyl mercaptan adsorbing material for an efficient decontamination has become a hot research topic. In this study, carbonization activation was employed with starch and urea as carbon and nitrogen sources, respectively, to prepare a type of starch-based activated carbon. Subsequently, the product was used to adsorb low-concentration methyl mercaptan. Based on sorption experiments and molecular simulations, the underlying mechanism of the adsorption effect of the adsorbent's pore structure and surface oxygen- and nitrogen-containing functional groups on methyl mercaptan molecules were discussed. The results indicated that when the methyl mercaptan equilibrium concentration was 0.197mg/L, the adsorption capacity of SUAC-16-2 for methyl mercaptan was 78.16mg/g. Its adsorption performance was better than that of its previously reported counterparts. The well-developed microporous structure of SUAC-16-2 promoted the adsorption of methyl mercaptan. In addition, methyl mercaptan molecules could be broken down to produce CH3S- and H+ by the effect of the surface functional groups. Adjacent carbon atoms containing nitrogen and oxygen functional groups could better adsorb CH3S- and H+, and further strengthen the methyl mercaptan adsorption performance of activated carbon. The study could help to develop new technology for treatment of low concentration of methyl mercaptan in the air.

Research on Intelligent Electronic Nose Based on Exhaled Breath to Detect Halitosis

Introduction Halitosis refers to the offensive or unpleasant gas emitted from the mouth, also known as oral odor. Previous studies have shown that 80-90% of halitosis patients are caused by oral diseases[1]. The patients with thick tongue coating and periodontal disease usually have obvious halitosis and the concentrations of hydrogen sulfide and methyl mercaptan in the breath of the oral cavity were significantly higher than those of the control group. Currently there are many methods for the diagnosis of halitosis in clinic. The commonly used direct measurement techniques include organoleptic measurement, gas chromatography and portable sulfide monitor[2]. Organoleptic measurement, which involves using the human nose to score the intensity of odours emanating from the patient’s mouth, is considered the gold standard for halitosis measurement[3]. Gas chromatography is expensive and complex to operate, which requires professionals to operate. Commercial portable gas chromatography such as Oral Chroma™ (Oral Chroma™, Abimedical, Abilit Corp., Osaka, Japan) can detect the concentration of hydrogen sulfide, methyl mercaptan and dimethyl sulfide, but its price is still relatively expensive. Portable sulfide monitor such as the Halimeter (Interscan Corp., Chatsworth, LA, USA) is specially used to measure the total concentration of sulfide. But it takes a long time to measure and is only suitable for clinical application.Based on the breath of patients with halitosis, this study uses an electrochemical sensor array to construct a small and intelligent electronic nose device for detecting bad breath, which realized the rapid quantitative detection of hydrogen sulfide and methyl mercaptan, and gave the preliminary screening results of halitosis grade and oral diseases. Method Halitosis samples were collected in the dental clinic. All patients had not smoked, drank or ate spicy food before the examination. The dentist first checks the patient's oral health, and then uses organoleptic measurement to evaluate the level of Halitosis. This information will be marked on the sampling bags. Finally, 100 ml exhaled air was collected with Tedlar sampling bag.The volatile sulfur compounds in 81 samples of breath were qualitatively and quantitatively detected using GC-MS(gas chromatography and mass spectrometry) in the laboratory. ROC method was used to establish the threshold model of halitosis grade. In addition, a diagnosis model of orogenic diseases based on linear discriminant analysis, logistic regression and support vector machine was established. On the basis of the measurement result, a small intelligent electronic nose device for halitosis detection was constructed with an electrochemical sensor array, and the calibration was carried out using hydrogen sulfide and methyl mercaptan standard gases. The device can establish a connection with the mobile phone through Bluetooth. The level threshold model of halitosis and the diagnosis model of oral diseases are transplanted into the app on the mobile phone. The diagnosis results can be calculated by substituting the concentration value transmitted by the device into the model. Results and Conclusions The halitosis level threshold model and oral disease diagnosis model show that halitosis can be heard when the total concentration of methyl mercaptan and hydrogen sulfide is greater than 0.2ppm. When the total concentration is greater than 0.4ppm, the patient's halitosis is very obvious. The severity of periodontal disease (including periodontitis and gingivitis) is significantly correlated with the concentration of methyl mercaptan. When the concentration ratio of methyl mercaptan to hydrogen sulfide is greater than 1:1, patients usually have obvious periodontitis. The size of the electronic nose device based on the diagnosis model is 50 mm × 50 mm × 25 mm and the detection range of methyl mercaptan and hydrogen sulfide is 0 to 2 ppm with a detection limit of 0.05 ppm. In addition, the response time and recovery time of the sensor array are both within 15s, which greatly shortens the time compared with the common clinical detection methods. The standard gases of hydrogen sulfide and methyl mercaptan are mixed with air to simulate the breath samples with different odor levels. The gas detection process is controlled by smart phones, and the respective concentrations of hydrogen sulfide and methyl mercaptan can be calculated within 15 seconds. Taking threshold model as the evaluation standard, the accuracy of the detection results is more than 90%, which indicates that the device has the potential to become a household or portable electronic nose for halitosis detection.

Lung tissue inflammatory response and pneumonocyte apoptosis of Sprague-Dawley rats after a 30-day exposure in methyl mercaptan vapor

ABSTRACT The objective of the research was to reveal the potential toxicity effects of methyl mercaptan on rat lung tissue. A dynamic exposure device and Sprague-Dawley (SD) rats were adopted. The exposure concentration of methyl mercaptan was 0.5 ± 0.1 ppm. The exposure procedure was 6 h/day, continuing for 30 days. The routine blood levels, oxidative stress levels in serum, immune molecule and cytokine in the serum and lung tissue were tested. Morphology injury of lung tissue was detected by Hematoxylin and Eosin (HE) staining. Apoptosis rate of alveolar epithelial cells were determined by TdT-mediated dUTP Nick End Labeling (TUNEL) assay. Reduction of body weight gain was observed in the male group during the exposure time, while there was no significant reduction of body weight gain in the female group. Pathological findings of terminal bronchiole constriction, alveolar congestion, and erythrocyte exudation confirmed the lung to be the main target organ. An apparent pneumonocyte apoptotic effection was also observed. Oxidative stress with lipid peroxidation, which affect blood antioxidant enzyme levels and induce apoptosis of alveolar epithelial cells, are recognized as a potential mechanism leading to terminal bronchiole constriction, alveoli congestion, and exudates of erythrocyte. Implications: The odor pollutants greatly affect the health of operation workers in the waste treatment plant, and odor complaints are becoming a major problem. The aim of this work is to identify the lung tissue inflammatory response of SD rats with chronic exposure to methyl mercaptan vapor at close to the recommended workplace concentration. In this study, we used a dynamic exposure device and chronic exposure model of rats to evaluate the potential toxicity effects of methyl mercaptan. The results showed that methyl mercaptan may cause lung inflammatory response and extensive lung cell apoptosis. Oxidative damage, with lipid peroxidation and alterations in blood antioxidant enzyme levels, was observed following methyl mercaptan exposure. This is recognized as a potential mechanism for terminal bronchiolar constriction, alveolar congestion, and erythrocyte exudation.

Field investigation of temporal variation of volatile organic compounds at a landfill in Hangzhou, China.

Variation of volatile organic compound (VOC) concentration and composition in an active landfill were monitored by a developed static chamber for 2years. The landfill gas from 82 sampling points including 70 points on working face, 8 points on geomembrane (GMB), and 4 points on final cover were analyzed for VOCs by GC-MS. Twenty-eight types of VOCs were detected, including terpenes, sulfur compounds, aromatics, hydrocarbon, oxygenated compounds, aldehyde compounds, and halogenated compounds. Terpenes were the dominant VOCs recorded in the spring, autumn, and winter seasons, whereas sulfur compounds dominated in the summer season. Limonene, ethyl alcohol, and acetone were identified as the main VOCs emitted from the waste working face of the landfill. Limonene dominated the terpenes with a maximum concentration of 43.29μgm-3 in the autumn season. Limonene was also the dominant VOC escaping from the defects of geomembrane temporary cover reaching an average concentration 38μgm-3. The defects of geomembranes can be a great emission source of VOCs. Emission rate of limonene was 2.24 times higher than that on the working face. VOC concentrations on the final cover can be 166 times less than those obtained on the working face. VOC emitted from the landfill did not represent a health threat for human health. However, concentrations of methyl mercaptan and ethanethiol on the working face were 3.4-22.8 times greater than their odor threshold, which were the main compounds responsible for odor nuisance. Results obtained from CALPUFF model indicated that methyl mercaptan and ethanethiol would not be a nuisance for the residents around the landfill. However, these compounds are harmful to the workers on the landfill.

Preliminary results of toxicity studies in rats following low-dose and short-term exposure to methyl mercaptan.

The present study was carried out to evaluate the hematotoxicity and respiratory toxicity of methyl mercaptan in Sprague-Dawley rats. A dynamic exposure methodology was adopted in this study following 7 days of exposure by repeated inhalation. The concentration of methyl mercaptan used in the exposure was 0.5 ppm and the exposure time was 6 h/day for 7 days. After exposure, the rats were sacrificed to collect lung tissue and blood samples. Routine blood and serum biochemistry were conducted. Morphological injury of lung tissue was detected by hematoxylin and eosin staining. Decreased food consumption and body weight gain in both sexes were noted in the exposure group compared with the control group. Several significant changes in hematological parameters were observed. The results showed that the blood urea nitrogen (UREA) levels and superoxide dismutase (SOD) values were significantly decreased in exposed male rats. Malondialdehyde (MDA) in lung tissue was significantly increased in both males and females in the exposed group. In the histopathological examination of lung tissue, terminal bronchiole constriction, alveolar congestion, and erythrocyte exudation were observed, suggesting that the lungs may be target organs after inhaling methyl mercaptan and workers exposed to this concentration may cause some pulmonary stimulation and injury.

Silver Ion Polyelectrolyte Container as a Sensitive Quartz Crystal Microbalance Gas Detector.

A polyelectrolyte film containing metastable silver ions was applied as a quartz crystal microbalance (QCM) gas detector. The polyelectrolyte film was obtained by immersing a polyelectrolyte with numerous amine groups in a metal ion solution. The QCM detector with silver ions responded to a very low methylmercaptan gas concentration (20 ppb) but did not respond to ammonia, volatile amines, aromatic compounds, or alcohols. The response speed of the QCM detector increased gradually with increasing methylmercaptan concentrations. The highly sensitive and selective response is promoted by a ligand substitution reaction caused by the formation of coordinative bonds between a metastable silver ion and amine groups in the polyelectrolyte film. To the best of our knowledge, this system has the highest sensitivity among reported QCM gas detectors. Such high-sensitivity among reported QCM gas detectors. Such high-sensitivity gas detectors for volatile sulfur compounds have wide ranging applications in areas such as volcanic eruption prediction, food inspection, environmental analysis, and medical diagnostics.

Inhibitory Effect of Enterococcus faecium WB2000 on Volatile Sulfur Compound Production by Porphyromonas gingivalis.

Volatile sulfur compounds (VSCs) produced by oral anaerobes are the major compounds responsible for oral malodor. Enterococcus faecium WB2000 is recognized as an antiplaque probiotic bacterium. In this study, the effect of E. faecium WB2000 on VSC production by Porphyromonas gingivalis was evaluated, and the mechanism of inhibition of oral malodor was investigated. P. gingivalis ATCC 33277 was cultured in the presence of four lactic acid bacteria, including E. faecium WB2000. Subsequently, P. gingivalis ATCC 33277, W50, W83, and two clinical isolates were cultured in the presence or absence of E. faecium WB2000, and the emission of VSCs from spent culture medium was measured by gas chromatography. The number of P. gingivalis ATCC 33277 in mixed culture with E. faecium WB2000 decreased at 6 h, and the rate of decrease was higher than that in mixed cultures with the other lactic acid bacteria. The numbers of five P. gingivalis strains decreased at similar rates in mixed culture with E. faecium WB2000. The concentration of methyl mercaptan was lower in spent culture medium from P. gingivalis and E. faecium WB2000 cultures compared with that from P. gingivalis alone. Therefore, E. faecium WB2000 may reduce oral malodor by inhibiting the growth of P. gingivalis and neutralizing methyl mercaptan.

Assessment of oral malodor and tonsillar microbiota after gargling with benzethonium chloride.

The oropharyngeal area can be a source of halitosis. However, the relationship between healthy tonsillar microbiota and halitosis is poorly understood. We conducted a pilot clinical study to clarify the effect of gargling with an antiseptic agent on tonsillar microbiota in patients with halitosis. Twenty-nine halitosis patients who did not have otolaryngologic disease or periodontitis were assigned randomly to one of three groups: benzethonium chloride (BZC) gargle; placebo gargle; no gargle. Concentrations of volatile sulfur compounds (VSCs) in mouth air, the organoleptic score (ORS) and tongue-coating score (TCS) were measured before and after testing. Tonsillar microbiota were assessed by detection of periodontal pathogens, and profiling with terminal-restriction fragment length polymorphism (T-RFLP) analysis and sequencing of 16SrRNA clone libraries for taxonomic assignment. Gargling with BZC reduced the concentrations of methyl mercaptan and hydrogen sulfide and the ORS, but did not affect the TCS or prevalence of periodontal pathogens. T-RFLP analyses and 16SrRNA clone sequencing showed a tendency for some candidate species to decrease in the test group. Although gargling of the oropharyngeal area with an antiseptic agent can reduce oral malodor, it appears that tonsillar microbiota are not influenced greatly. (J Oral Sci 58, 83-91, 2016).

Dietary composition affects odour emissions from meat chickens.

Abatement of odour emissions has become an important consideration to agricultural industries, including poultry production. The link between diet and odour emissions was studied in two experiments using Ross 308 male meat chickens reared in specially designed chambers in a climate controlled room. In the first experiment, two treatments were compared using three replicates of two birds per chamber. Two wheat-soy based treatment diets were formulated with or without canola seed, an ingredient rich in sulfur amino acids. Treatment 1 (T1) had 13.39 MJ/kg ME (as fed) and used 60 g/kg canola seed without corn while Treatment 2 (T2) contained 12.90 MJ/kg ME (as fed) and used 150 g/kg corn without canola seed. In the second experiment, birds were assigned to three dietary treatments of five replicates with five birds per replicate (chamber). The basal starter, grower and finisher diets in the control group (SBM group) contained soybean meal in the range of 227–291 g/kg (as fed) as the main protein source. The other treatments (CM and MBM groups) contained either high levels of canola meal (174–190 g/kg) or meat meal (74–110 g/kg) at the expense of soybean meal. In both experiments, diets were isocaloric, isonitrogenous and contained similar digestible amino acid contents as per 2007 Aviagen Ross 308 guidelines. Emissions of odour were measured using Fourier transform infrared (FTIR) spectroscopy. In both experiments, major odorous compounds detected included 2,3-butanedione (diacetyl), 2-butanone, dimethyl disulfide, methyl mercaptan, ethyl mercaptan, 2-butanol, 3-methyl-butanal, phenol and m-cresol. In the first experiment, T1 (with canola seed) produced higher concentration of methyl mercaptan (P < 0.05) and lower diacetyl (P < 0.01) than T2. In the second experiment, methyl mercaptan emission was higher in SBM group (P = 0.01) and total elemental sulfur were higher in SBM and CM groups up to day 24 (P < 0.01). Results of these experiments indicated a direct link between diet and odour emissions from meat chickens.

Influence of methyl mercaptan on the repair bond strength of composites fabricated using self-etch adhesives.

The influence of methyl mercaptan on the repair bond strength of composites fabricated using self-etch adhesives was investigated. The surface free-energies were determined by measuring the contact angles of test liquids placed on composites that had been immersed in different concentrations of methyl mercaptan (0.01, 0.1, and 1.0 M). To determine the repair bond strength, self-etch adhesives were applied to the aged composite, and then newly added composites were condensed. Ten samples of each specimen were subjected to shear testing at a crosshead speed of 1.0 mm min(-1). Samples were analyzed using two-way ANOVA followed by Tukey's honestly significant difference (HSD) test. Although the dispersion force of the composites remained relatively constant, their polar force increased slightly as the concentration of methyl mercaptan increased. The hydrogen-bonding forces were significantly higher after immersion in 1.0 M methyl mercaptan, leading to higher surface-free energies. However, the repair bond strengths for the repair restorations prepared from composites immersed in 1.0 M methyl mercaptan were significantly lower than for those immersed in 0.01 and 0.10 M methyl mercaptan. Considering the results of this study, it can be concluded that the repair bond strengths of both the aged and newly added composites were affected by immersion in methyl mercaptan solutions.

The method for on-site determination of trace concentrations of methyl mercaptan and dimethyl sulfide in air using a mobile mass spectrometer with atmospheric pressure chemical ionization, combined with a fast enrichment/separation system.

A method for fast simultaneous on-site determination of methyl mercaptan and dimethyl sulfide in air was developed. The target compounds were actively collected on silica gel, followed by direct flash thermal desorption, fast separation on a short chromatographic column and detection by means of mass spectrometer with atmospheric pressure chemical ionization. During the sampling of ambient air, water vapor was removed with a Nafion selective membrane. A compact mass spectrometer prototype, which was designed earlier at Trofimuk Institute of Petroleum Geology and Geophysics, was used. The minimization of gas load of the atmospheric pressure ion source allowed reducing the power requirements and size of the vacuum system and increasing its ruggedness. The measurement cycle is about 3 min. Detection limits in a 0.6 L sample are 1 ppb for methyl mercaptan and 0.2 ppb for dimethyl sulfide.

The detection of Candida species in patients with halitosis.

To examine the effects of Candida on halitosis, the carrier state of Candida was examined in patients who made a visit with a chief complaint of halitosis. Methods. Subjects were 123 patients (42 males and 81 females) who visited our clinic, with a chief complaint of halitosis. Their average age was 45.8 years. To examine halitosis, an organoleptic test was conducted, and volatile sulfur compounds (VSCs) were measured by gas chromatography. Tongue-coating samples collected at the initial visit were cultured in CHROMagar Candida medium. The results of a Candida culture test, an organoleptic test, and VSC measurements were examined. Results. The male-to-female ratio of the patients was about 1 : 2. Patients with severe halitosis accounted for less than 20%. In the Candida culture test, the positive rate was about 25.2%, and C. albicans was the most frequently detected. Two kinds of Candida species were detected in 75% (6/8) of the strongly Candida-positive group. The VSC measurements were correlated with the Candida culture test results. Methyl mercaptan concentration was higher in the strongly C. albicans-positive group or the subjects having two kinds of Candida species. Conclusion. We suggest that imbalance of oral microbial community exists in the strongly Candida-positive group.

Supervised machine learning-based classification of oral malodor based on the microbiota in saliva samples

This study presents an effective method of classifying oral malodor from oral microbiota in saliva by using a support vector machine (SVM), an artificial neural network (ANN), and a decision tree. This approach uses concentrations of methyl mercaptan in mouth air as an indicator of oral malodor, and peak areas of terminal restriction fragment (T-RF) length polymorphisms (T-RFLPs) of the 16S rRNA gene as data for supervised machine-learning methods, without identifying specific species producing oral malodorous compounds. 16S rRNA genes were amplified from saliva samples from 309 subjects, and T-RFLP analysis was carried out with the DNA fragments. T-RFLP analysis provides information on microbiota consisting of fragment lengths and peak areas corresponding to bacterial strains. The peak area is equivalent to the frequency of a specific fragment when one molecule is selected from terminal fragments. Another frequency is obtained by dividing the number of species-containing samples by the total number of samples. An SVM, an ANN, and a decision tree were trained based on these two frequencies in 308 samples and classified the presence or absence of methyl mercaptan in mouth air from the remaining subject. The proportion that trained SVM expressed as entropy achieved the highest classification accuracy, with a sensitivity of 51.1% and specificity of 95.0%. The ANN and decision tree provided lower classification accuracies, and only classification by the ANN was improved by weighting with entropy from the frequency of appearance in samples, which increased the accuracy to 81.9% with a sensitivity of 60.2% and a specificity of 90.5%. The decision tree showed low classification accuracy under all conditions. Using T-RF proportions and frequencies, models to classify the presence of methyl mercaptan, a volatile sulfur-containing compound that causes oral malodor, were developed. SVM classifiers successfully classified the presence of methyl mercaptan with high specificity, and this classification is expected to be useful for screening saliva for oral malodor before visits to specialist clinics. Classification by a SVM and an ANN does not require the identification of the oral microbiota species responsible for the malodor, and the ANN also does not require the proportions of T-RFs.

Design and characterization of methyl mercaptan biosensor using alcohol oxidase

A bi-enzyme biosensor, alcohol oxidase (AOX) and osmium-wired horseradish peroxidase (Os-HRP) modified carbon screen printed electrode (SPE), was designed for detection of methyl mercaptan in aqueous phase. Alcohol oxidase was found to catalytically oxidize methyl mercaptan to yield H2O2, sulfide and formaldehyde. Product H2O2 could be detected electrochemically to evaluate the concentration of methyl mercaptan. The detection limit of this biosensor to methyl mercaptan in aqueous phase is 0.2μM.

Installation for air cleaning from organic impurities by plasma formed by barrier discharge of nanosecond duration

A prototype installation for air cleaning by plasma, which consists of a barrier-type discharge reactor and a high-voltage nanosecond-pulse supply generator, which is based on drift step recovery diodes, is considered. A stable corona-type barrier discharge was obtained at a 3-kHz supply-pulse repetition frequency. The discharge remained nonlocalized even at a small gas-discharge gap (∼6 mm) due to a short (∼25 ns) pulse duration, which allows a quite uniform effect on the air flow. The high rise rate (∼6 kV/ns) of the applied supply voltage pulses determines the high voltage amplitude (∼25 kV) at the reactor at the breakdown moment and allows maintenance of high electric-field intensity and a high intensity of plasma chemical processes. Thus, an electrical power lower than 8 W is required at the reactor input to produce 1 g of ozone per hour. The concentration of methylmercaptan in air during waste-water smell deodorizing at State Unitary Enterprise “Vodokanal of St. Petersburg” was reduced down to an allowable level of 0.5 mg/m3 at the electrical power consumption no higher than 0.25 W per cubic meter of air.

Comparison of the Use of the Halimeter and the Oral Chroma™ in the Assessment of the Ability of Common Cultivable Oral Anaerobic Bacteria to Produce Malodorous Volatile Sulfur Compounds from Cysteine and Methionine

Objective: To compare the use of the Halimeter and the Oral Chroma™ to assess the ability of common oral anaerobic bacteria isolated from the Kuwaiti population to produce volatile sulfur compounds (VSCs). Materials and Methods: Broth cultures of common anaerobes isolated from supragingival plaque were centrifuged and pellets resuspended in phosphate buffer (pH 7.7) with an optical density OD₅₅₀ of 0.3. 100 µl of this suspension and 870 µl of buffer were added in 2 sterile 15-ml head space vials. Reaction was initiated by addition of 30 µl of 33 mML-methionine and L-cysteine, respectively, in each vial and incubation at 37°C for 90 min. 500 µl of 3 M phosphoric acid was added to tubes and was kept aside for 10 min. Production of VSCs was measured using the Halimeter and the Oral Chroma. Results: The major VSC producers identified by both Halimeter and Oral Chroma with L-cystenine as substrate were Campylobacter ureolyticus, Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia, Aggregatibacter actinomycetemcomitans and Gemella morbillorum. The concentrations of hydrogen sulfide recorded by both Halimeter and Oral Chroma were essentially identical. With L-methionine as substrate, both Halimeter and Oral Chroma identified different complements of anaerobes with C. ureolyticus,P. gingivalis,Fusobacterium nucleatum and P. intermedia as major VSC producers. The concentrations of methyl mercaptan recorded by the Halimeter were lower compared to those assessed by the Oral Chroma. Conclusion: The results suggest that the Oral Chroma may produce a more comprehensive assessment of VSC production by oral microflora than the Halimeter.

High-Temperature Pyrolysis of Blended Animal Manures for Producing Renewable Energy and Value-Added Biochar

In this study, we used a commercial pilot-scale pyrolysis reactor system to produce combustible gas and biochar at 620 °C from three sources (chicken litter, swine solids, mixture of swine solids with rye grass). Pyrolysis of swine solids produced gas with the greatest higher heating value (HHV) followed by the mixture of swine solids with rye grass and chicken litter. Relatively high S-containing gases were produced; dimethyl sulfide and methyl mercaptan concentrations were higher than the OSHA PEL limits. Biochar yield ranged from 43 to 49% based on dry weight with about 53% of carbon recovery. Whereas the HHV of the chicken litter biochar was slightly below that of low rank coals, swine-based biochars had HHVs between high and low rank coals. Approximately 50% of the feedstock energy was retained in biochar and 25% in produced gases. Manure biochars contained higher concentrations of P and K than that of original manure feedstocks. Consequently, these could be used as a low-grade fertilizer to improve ...

Influence of methyl mercaptan at early setting stages on the properties of self curing addition silicone resilient denture lining materials

The aim of the present study was to clarify the influence of early setting conditions on the properties of self curing addition silicone resilient denture lining materials. Four auto-mix types of commercial self curing addition silicone resilient denture lining materials were used. Agar plates containing various concentrations of methyl mercaptan (MMP) were prepared and cylindrical specimens (10mm in height and 10mm in diameter) of silicone liners were set on the agar plate. The Shore A hardness of the agar-contacted surface of the specimen was measured at 0, 1, 7 and 28 days after stored in 37 degrees C water. The viscoelastic properties (instantaneous elastic modulus, coefficient of viscosity and permanent deformation) of two silicone liners, which showed a great decrease in the Shore A hardness by agar contact, were determined by a creep meter. The Shore A hardness, coefficient of viscosity, and instantaneous elastic modulus deceased when the specimen was set on the MMP containing agar plate, but the permanent deformation of these specimens increased. The exposure to MMP at the early setting stage influenced the properties of self curing addition silicone resilient denture lining materials.