[Riess2010] "Experimental setup and analytical methods for the non-invasive determination of volatile organic compounds, formaldehyde and NOx in exhaled human breath.",
Anal Chim Acta
, vol. 669, no. 1-2: Hannover Medical School, Sports Physiology and Sports Medicine, Carl-Neuberg-Str. 1, 30625 Hannover, Germany., pp. 53–62, Jun, 2010.
Different analytical devices were tested and evaluated for their suitability of breath gas analysis by examining the physiological parameters and chemical substances in the exhaled breath of ten healthy probands during light cycling in dependence of methanol-rich nutrition. The probands exercised under normal breathing conditions on a bicycle ergometer. Breath air was exhaled into a glass cylinder and collected under steady-state conditions. Non-invasively measured parameters were pulse rate, breath frequency, temperature, relative humidity, NO(x), total volatile organic compounds (TVOC(PAS)), carbon dioxide (CO(2)), formaldehyde, methanol, acetaldehyde, acetone, isoprene and volatile organic compounds (VOCs). Methanol rich food and beverages strongly influenced the concentration of methanol and other organic substances in human breath. On the other hand, nutrition and smoking had no clear effect on the physical conditions of the probands. The proton transfer reaction mass spectrometry (PTR-MS) method was found to be very suitable for the analysis of breath gas but the m/z 31, if assigned to formaldehyde, is sensitive to interferences. The time vs. concentration curves of nitric oxide showed sudden peaks up to 120ppb in most of the measurements. In one case a strong interference of the NO(x) signal was observed. The time resolved analysis of exhaled breath gas is of high capability and significance for different applications if reliable analytical techniques are used. Some compounds like nitric oxide (NO), methanol, different VOCs as well as sum parameters like TVOC(PAS) are especially suitable as markers. Formaldehyde, which is rapidly metabolized in the human body, could be measured reliably as a trace component by the acetylacetone (acac) method but not by PTR-MS.
[Schripp2010] "Interferences in the determination of formaldehyde via PTR-MS: What do we learn from m/ z 31?",
International Journal of Mass Spectrometry
, vol. 289, no. 2: Elsevier, pp. 170–172, 2010.
The determination of trace levels of formaldehyde in air via Proton-Transfer-Reaction-Mass-Spectrometry (PTR-MS) has been reported in several publications. Especially in case of breath analysis – an important field for PTR-MS measurements – relatively high formaldehyde concentrations were found. However, due to the low mass of the target compound interferences from fragment ions of larger molecules are likely. In this study breath analysis aiming at the determination of formaldehyde via PTR-MS and online-formaldehyde analysis (basing on the Hantzsch reaction) is performed. The presence of alcohols obviously increased the amount of detected m/z 31 while no change of the online-analyzer signal occurred. Additionally, the determination of the rate constant kf of the formaldehyde ionization in the PTR-MS is performed on the basis of emission chamber tests. The results illustrate the vast complications when quantifying formaldehyde in air via PTR-MS at m/z 31.