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CO2 Laser Photoacoustic Spectroscopy 

Laser spectroscopy is a successful tool for the detection of specific gases with high sensitivity and fast time response. Optical detection techniques have to operate in the so-called "molecular fingerprint region", located in the near IR wavelength range (between 9.2 and 10.8 μm) of the CO2 laser. The CO2 LPAS system can detect various gases, such as ethylene, with a minimum of 0.9 ppb and up to 100 ppm and this system offers many advantages:

- the responsivity is independent of the wavelength of radiation;
- immune to interference, high sensitivity;
- real time analysis with quasi continuous measurements;
- operational simplicity.  

We designed two experimental set-ups with the photoacoustic cell in an external configuration:     

The CO2 Laser Photoacoustic Spectroscopy has applications in:

Human health related investigations:

The analysis of human breath for (early) diagnosis of diseases is a promissing emerging technique, with direct application in areas such as public health and quality of life improvement. In clinical medicine, breath testing is the least invasive of all diagnostic tests, presenting minimal risk and negligible discomfort to patients.

Trace gas analysis of the breath composition gives information about various processes occurring inside the human body. For example, lipid peroxidation is of major interest as the free radicals induce an oxidative degradation of the polyunsaturated fatty acids, causing cell damage and cell death. In normal situations, free radical formation and antioxidants are balanced. However, under certain conditions (e.g. UV radiation, ionising radiation (X-ray) trauma, pulmonary and skin diseases, heart failure, diabetes, mental disorders, cigarette smoke, etc.) this balance is disturbed. The levels of ethylene (C2H4) are an indicator of lipid peroxidation in humans.The breath ammonia level can serve for determining the exact time necessary for optimal degree of dialysis for a patient with end-stage renal disease at every session. 

Environmental monitoring: 

Molecular gases of environmental interest can be identified and measured quantitatively (ethanol, methanol, carbon dioxide). 

Other potential applications refer to the detection of explosives and to the analysis of surgical smoke, known to contain gases such as acroleine, acetonitrile, ammonia, benzene, ethylene, methanol, toluene.

Plant physiology investigations: 

Ethylene acts as a vegetal hormone produced by all plant tissues and it is transported by diffusion through the plant tissues, increasing the plasmatic membrane permeability and having multiple effects on the cell metabolism. More specifically, it enhances the oxidative processes, facilitating the transport inside the cells and the biodegradation of the organic acids and chlorophyll, therefore playing a major role in many metabolic processes.