Comparison of sampling bags for the analysis of volatile organic compounds in breath.

Nalophan, Tedlar and Cali-5-Bond polymeric bags were compared to determine the most suitable type for breath sampling and storage when volatile organic compounds are to be determined. Analyses were performed by thermal desorption gas chromatography mass spectrometry. For each bag, the release of contaminants and the chemical stability of a gaseous standard mixture containing eighteen organic compounds, as well as the CO2 partial pressure were assessed. The selected compounds were representative of breath constituents and belonged to different chemical classes (i.e. hydrocarbons, ketones, aldehydes, aromatics, sulfurs and esters). In the case of Nalophan, the influence of the surface-to-volume ratio, related to the bag's filling degree, on the chemical stability was also evaluated. Nalophan bags were found to be the most suitable in terms of contaminants released during storage (only 2-methyl-1,3-dioxalane), good sample stability (up to 24 h for both dry and humid samples), and very limited costs (about 1 € for a 20 liter bag). The (film) surface-to-(sample) volume ratio was found to be an important factor affecting the stability of selected compounds, and therefore we recommended to fill the bag completely.

Monitoring breath during oral glucose tolerance tests.

The evolution of breath composition during oral glucose tolerance tests (OGTTs) was analysed by thermal desorption/gas chromatography/mass spectrometry in 16 subjects and correlated to blood glucose levels. The glucose tolerance tests classified five of the subjects as diabetics, eight as affected by impaired glucose tolerance and three as normoglycaemic. Acetone levels were generally higher in diabetics (average concentration values: diabetics, 300 ± 40 ppbv; impaired glucose tolerance, 350 ± 30 ppbv; normoglycaemic, 230 ± 20 ppbv) but the large inter-individual variability did not allow us to identify the three groups by this parameter alone. The exhalation of 3-hydroxy-butan-2-one and butane-2,3-dione, likely due to the metabolization of glucose by bacteria in the mouth, was also observed. Future work will involve the extension of the analyses to other volatile compounds by attempting to improve the level of discrimination between the various classes of subjects.

Cumulative exposure assessment for trace-level polycyclic aromatic hydrocarbons (PAHs) using human blood and plasma analysis.

Humans experience chronic cumulative trace-level exposure to mixtures of volatile, semi-volatile, and non-volatile polycyclic aromatic hydrocarbons (PAHs) present in the environment as by-products of combustion processes. Certain PAHs are known or suspected human carcinogens and so we have developed methodology for measuring their circulating (blood borne) concentrations as a tool to assess internal dose and health risk. We use liquid/liquid extraction and gas chromatography-mass spectrometry and present analytical parameters including dynamic range (0-250 ng/ml), linearity (>0.99 for all compounds), and instrument sensitivity (range 2-22 pg/ml) for a series of 22 PAHs representing 2-6-rings. The method is shown to be sufficiently sensitive for estimating PAHs baseline levels (typical median range from 1 to 1000 pg/ml) in groups of normal control subjects using 1-ml aliquots of human plasma but we note that some individuals have very low background concentrations for 5- and 6-ring compounds that fall below robust quantitation levels.

Application of novel method to measure endogenous VOCs in exhaled breath condensate before and after exposure to diesel exhaust.

Polar volatile organic compounds (PVOCs) such as aldehydes and alcohols are byproducts of normal human metabolism and thus are found in blood and exhaled breath. Perturbation of the normal patterns of such metabolites may reflect exposures to environmental stressors, disease state, and human activity. Presented herein is a specific methodology for assaying PVOC biomarkers in exhaled breath condensate (EBC) samples with application to a series of samples from a controlled chamber exposure to dilute diesel exhaust (DE) or to purified air. The collection/analysis method is based on condensation of normal (at rest) exhaled breaths for 10 min (resulting in 1-2 ml of liquid) with subsequent analyte adsorption onto Tenax cartridges followed by thermal desorption and analysis by gas chromatography/mass spectrometry (GC/MS). Analytical data have linearity of response (R(2)>0.98) across a range of 0-160 ng/ml with a detection limit ranging from 0.2 to 7 ng/ml depending on the compound. Statistical analyses of the results of the controlled exposure study indicate that metabolism, as reflected in simple breath-borne oxygenated species, is not affected by exposure to ambient airborne levels of DE. Linear mixed-effects models showed that PVOC biomarker levels are affected by gender and vary significantly among nominally healthy subjects. Differences among PVOCs analyzed in clinic air, purified chamber air, and chamber air containing dilute DE confirm that most of the compounds are likely of endogenous origin as the exogenous exposure levels did not perturb the EBC measurements.

Implementation of Fowler's method for end-tidal air sampling.

The design, realization and testing of a CO(2)-triggered breath sampler, capable of a separate collection of dead space and end-tidal air on multiple breaths, is presented. This sampling procedure has advantages in terms of the sample volume, insights regarding the origin of compounds, increased reproducibility and higher concentrations of compounds. The high quality of design and the speed of the components ensure a breath-by-breath estimate of dead volume, as well as the comfort and safety of the subject under test. The system represents a valid tool to contribute to the development of a standardized sampling protocol needed to compare results obtained by the various groups in this field.