The measurements and results of TRACELIFE (TE50) project were implemented using the LPAS system developed at National Institute for Laser, Plasma and Radiation Physics, Optics and Lasers in Life Sciences, Environment and Manufacturing laboratory, Bucharest, Romania.
The experimental setup consists of a line-tunable CO2 laser emitting radiation in the 9.2 - 10.8 mm region on 73 different vibrational-rotational lines and a photoacoustic cell (PA), where the gas is detected. The requirement for gases to be detected with this sensitive laser is that they should possess high absorption strength and a characteristic absorption pattern in the wavelength range of the CO2 laser (e.g. 10.53 mm for ethylene and 9.22 mm for ammonia).
Inside the PA, traces of ethylene and ammonia can absorb the laser radiation and the absorbed energy is released into heat, which creates an increase in pressure inside a closed volume. By modulating the laser beam with a mechanical chopper, pressure waves are generated and detected with four sensitive miniature microphones mounted in the cell wall. There electric signal is fed into a dual-phase, digital lock-in amplifier and its filtered output signal is introduced in the data acquisition interface. All experimental data are processed in real time and stored by a computer. Another important element of the system is the gas handling system due to its role in ensuring gas purity in the PA cell. It can be used to pump out the cell, to introduce the sample gas in the PA cell at a controlled flow rate, and monitor the total and partial pressures of gas mixtures.
To increase the accuracy of LPAS method for measurements of biomarkers in exhaled air of subjects, we took several supplementary measures, such as aluminium-coated plastic bags for preserving the sample gas, or traps filled with potassium hydroxide (KOH) for retention of the CO2, and CaCl2 or CaSO4 (known as Drierite) for filtration of water vapors.Results dissemination :
- C. Popa and C. Matei, Optoelectronics and Advanced Materials - Rapid Communications OAM-RC 5 (11-12): 1237-1242 (2011).
- M. Petrus, C. Matei, M. Paţachia and D.C. Dumitras , Journal of Optoelectronics and Advanced Materials 14 (7-8): 664-670 (2012) .
- C. Popa, M. Paţachia, S. Băniţă and D. C. Dumitraşaccepted to be published in Revue Roumaine de Chimie - RRC, vol. 58, nr. 9 (2013).
- Ş. Băniţă, C. Popa, M. Paţachia and D. C. Dumitraş, “Ethylene concentration at fruits under aerobic vs. anaerobic conditions”, U.P.B Sci. Bull., Series A, Vol. 75, No. 3, pp. 217-226 (2013) .