The role of mathematical modeling in VOC analysis using isoprene as a prototypic example

Isoprene is one of the most abundant endogenous volatile organic compounds (VOCs) contained in human breath and is considered to be a potentially useful biomarker for diagnostic and monitoring purposes. However, neither the exact biochemical origin of isoprene nor its physiological role are understood in sufficient depth, thus hindering the validation of breath isoprene tests in clinical routine. Exhaled isoprene concentrations are reported to change under different clinical and physiological conditions, especially in response to enhanced cardiovascular and respiratory activity. Investigating isoprene exhalation kinetics under dynamical exercise helps to gather the relevant experimental information for understanding the gas exchange phenomena associated with this important VOC. A first model for isoprene in exhaled breath has been developed by our research group. In the present paper, we aim at giving a concise overview of this model and describe its role in providing supportive evidence for a peripheral (extrahepatic) source of isoprene. In this sense, the results presented here may enable a new perspective on the biochemical processes governing isoprene formation in the human body.Comment: 17 page

Isoprene and acetone concentration profiles during exercise on an ergometer

A real-time recording setup combining exhaled breath VOC measurements by proton transfer reaction mass spectrometry (PTR-MS) with hemodynamic and respiratory data is presented. Continuous automatic sampling of exhaled breath is implemented on the basis of measured respiratory flow: a flow-controlled shutter mechanism guarantees that only end-tidal exhalation segments are drawn into the mass spectrometer for analysis. Exhaled breath concentration profiles of two prototypic compounds, isoprene and acetone, during several exercise regimes were acquired, reaffirming and complementing earlier experimental findings regarding the dynamic response of these compounds reported by Senthilmohan et al. [1] and Karl et al. [2]. While isoprene tends to react very sensitively to changes in pulmonary ventilation and perfusion due to its lipophilic behavior and low Henry constant, hydrophilic acetone shows a rather stable behavior. Characteristic (median) values for breath isoprene concentration and molar flow, i.e., the amount of isoprene exhaled per minute are 100 ppb and 29 nmol/min, respectively, with some intra-individual day-to-day variation. At the onset of exercise breath isoprene concentration increases drastically, usually by a factor of ~3-4 within about one minute. Due to a simultaneous increase in ventilation, the associated rise in molar flow is even more pronounced, leading to a ratio between peak molar flow and molar flow at rest of ~11. Our setup holds great potential in capturing continuous dynamics of non-polar, low-soluble VOCs over a wide measurement range with simultaneous appraisal of decisive physiological factors affecting exhalation kinetics.Comment: 35 page

Expiratory flow rate, breath hold and anatomic dead space influence electronic nose ability to detect lung cancer

BACKGROUND: Electronic noses are composites of nanosensor arrays. Numerous studies showed their potential to detect lung cancer from breath samples by analysing exhaled volatile compound pattern ("breathprint"). Expiratory flow rate, breath hold and inclusion of anatomic dead space may influence the exhaled levels of some volatile compounds; however it has not been fully addressed how these factors affect electronic nose data. Therefore, the aim of the study was to investigate these effects. METHODS: 37 healthy subjects (44 +/- 14 years) and 27 patients with lung cancer (60 +/- 10 years) participated in the study. After deep inhalation through a volatile organic compound filter, subjects exhaled at two different flow rates (50 ml/sec and 75 ml/sec) into Teflon-coated bags. The effect of breath hold was analysed after 10 seconds of deep inhalation. We also studied the effect of anatomic dead space by excluding this fraction and comparing alveolar air to mixed (alveolar + anatomic dead space) air samples. Exhaled air samples were processed with Cyranose 320 electronic nose. RESULTS: Expiratory flow rate, breath hold and the inclusion of anatomic dead space significantly altered "breathprints" in healthy individuals (p 0.05). These factors also influenced the discrimination ability of the electronic nose to detect lung cancer significantly. CONCLUSIONS: We have shown that expiratory flow, breath hold and dead space influence exhaled volatile compound pattern assessed with electronic nose. These findings suggest critical methodological recommendations to standardise sample collections for electronic nose measurements

Application of medical and analytical methods in Lyme borreliosis monitoring

Lyme borreliosis (LB) is one of the most common tick-borne diseases in the northern hemisphere. It is a chronic inflammatory disease caused by the spirochaete Borrelia burgdorferi. In its early stages, pathological skin lesions, namely erythema chronicum migrans, appear. The lesions, usually localised at the site of the bite, may become visible from a few weeks up to 3 months after the infection. Predominant clinical symptoms of the disease also involve joint malfunctions and neurological or cardiac disorders. Lyme disease, in all its stages, may be successfully treated with antibiotics. The best results, however, are obtained in its early stages. In order to diagnose the disease, numerous medical or laboratory techniques have been developed. They are applied to confirm the presence of intact spirochaetes or spirochaete components such as DNA or proteins in tick vectors, reservoir hosts or patients. The methods used for the determination of LB biomarkers have also been reviewed. These biomarkers are formed during the lipid peroxidation process. The formation of peroxidation products generated by human organisms is directly associated with oxidative stress. Apart from aldehydes (malondialdehyde and 4-hydroxy-2-nonenal), many other unsaturated components such as isoprostenes and neuroprostane are obtained. The fast determination of these compounds in encephalic fluid, urine or plasma, especially in early stages of the disease, enables its treatment. Various analytical techniques which allow the determination of the aforementioned biomarkers have been reported. These include spectrophotometry as well as liquid and gas chromatography. The analytical procedure also requires the application of a derivatization step by the use of selected reagents

Sorbents for Trapping Organic Pollutants From Air

A series of siliceous adsorbents with chemically bonded phases (CBPs) of different polarity were tested as sorbents for trapping air pollutants (petroleum ether) using controlled setup. Moreover, special attention was paid to the potential role of metal impurities as strong adsorption sites. Sorbents were characterized by various physico-chemical methods, such as porosimetry, inductively coupled plasma (ICP) analysis, elemental analysis, derivatography, and gas hromatography. Trapping tubes were utilized for sorption of toxic pollutants from indoor air

Using Gas Chromatography for Indoor-Air Quality Control in Conservation and Renovation Studios

Investigations were carried out in the Department of Conservation of Painting and Polychrome Sculpture and in the Screen Printing Studio of the Faculty of Art at Nicolaus Copernicus University. Concentration of the vapours of organic solvents was measured in 2 workshops: the Art Conservation Studio and the Screen Printing Studio. This study attempts to evaluate the work environment in both studios by analysing the concentration of vapour solvents over 5 to 7 years of measurements. Volatile solvents—aliphatic and aromatic hydrocarbons, alcohols, esters and ketones—were detected in investigated workplaces. These compounds have a wide range of applications in cleaning and removing old varnishes, lacquers and paints; inhalation is the main route of exposure. Vapour was collected using an active sampling method

Effect of diversified hen raising system on lutein content in eggs

Zainteresowanie karotenoidami wynika z ich znaczenia w żywieniu człowieka. Szczególnie luteina oraz zeaksantyna spełniają ważną funkcję w procesie widzenia, a także w profilaktyce chorób cywilizacyjnych. Celem pracy było porównanie zawartości luteiny w jajach pochodzących od niosek ze zróżnicowanego systemu chowu (klatkowy, ściółkowy, wolno wybiegowy) oraz ocena sensoryczna badanych jaj. Największą zawartość luteiny oznaczono w jajach pochodzących od kur z chowu wolnowybiegowego (średnio o ponad 50 % więcej w porównaniu z innymi grupami). Jaja te zostały wyróżnione także przez panel sensoryczny pod względem smaku (4,9 pkt) oraz zapachu (4,8 pkt). Jaja pochodzące z chowu fermowego, wzbogacone w wielonienasycone kwasy tłuszczowe oraz wit. A + E charakteryzowały się najmniejszą zawartością luteiny (0,21 mg/jajo). Surowiec standardowy, pochodzący od niosek z fermy towarowej, cechował się najwyższym stopniem wybarwienia żółtka (14,8) przy jednoczesnym wysokim poziomie oznaczonego karotenoidu (0,37 mg/jajo).The interest in carotenoids results from their importance in human nutrition. Particularly, lutein and zeaxanthin play a vital role in the process of seeing, as well as in the lifestyle disease prophylaxis. The objective of the study was to compare the content of lutein in eggs laid by hens from a diversified raising system (cage, bedding, and free-range system) and to sensory assess the eggs under analysis. The highest content of lutein was determined in eggs laid by hens kept in a free-range system (over 50 % on average compared to other groups). These eggs were also emphasised in the sensory panel as those with the best taste (4.9) and aroma (4.8). The eggs, laid by hens raised in a poultry farming system and enriched with polyunsaturated fatty acids and vitamins A+E, were characterized by the lowest content of lutein (0.21mg/egg). The standard material, obtained from laying hens raised in a commercial farm, was characterized by the highest egg yolk coloration (14.8) and, at the same time, by a high level of carotenoid determined (0.37mg/egg)

Determination of phenolic derivatives of antipyrine in plasma with solid-phase extraction and high-performance liquid chromatography-atmospheric-pressure chemical ionization mass spectrometry

This manuscript describes a method to determine antipyrine and its phenolic derivatives in plasma by reversed-phase high-performance liquid chromatography–mass spectrometry (RP-HPLC–MS). The sample pretreatment consisted of a C18 solid-phase extraction (SPE), to remove the salts and proteins. The retention behavior of antipyrine and its phenolic derivatives in the SPE procedure was estimated by the k values determined on a C18 HPLC column at different pH values and with different buffer compositions. Recoveries of antipyrine and its phenolic products were 90% in water and 100% in plasma. Atmospheric pressure chemical ionization (APCI) was used to introduce the components into the mass spectrometer. The mass spectrometer was operated in the single ion monitoring mode (SIM mode) as well as in the selective reaction (SR) mode. The SR mode or tandem MS resulted in the best signal-to-noise ratio, with a detection limit for antipyrine of 6 pg in 20 µl. For the different phenolic antipyrines, different target ions were used and conditions were optimized for each