Quantitative analysis of metabolic gases by multichannel raman spectroscopy: use of a newly designed elliptic–spherical integration type of cell holder

Abstract

We describe the quantitative analysis of some metabolic gases bymultichannel Raman spectroscopy. Raman spectra were measured forair, acetone, ammonia, carbon dioxide, and mixed gas consisting ofacetone, ammonia, and air. We designed a new elliptic-sphericalintegration type of cell holder to obtain the Raman spectra of gaseswith a high signal-to-noise ratio. Concentrations of acetone, ammonia, and carbon dioxide were determined by the peak intensities ofRaman bands at 2940, 3228, and 1385 cm(-1), respectively. To compensate for the fluctuations of Ramanintensities caused by several factors, such as the fluctuations oflaser power, the peak intensity of a band at 2324 cm(-1) dueto nitrogen gas was used as an internal intensity standard. Thecorrelation coefficient between the corrected Raman intensity at 2940cm(-1) and the concentration of acetone was calculated to be0.984 for a concentration range of 2-12 ppm. The detection limitof acetone gas was found to be 2 ppm.

Photonic bandgap fiber-enabled Raman detection of nitrogen gas

“…This factor is usually called the instrument factor (K). Therefore, a simplified equation for the observed Raman Scatter can be expressed as follows [1] R = I 0 c J(λ) K(λ) / λ 4 ( 1 ) Clearly, if the experimental conditions are controlled, Raman spectroscopy should be capable of quantitative analysis. Using the same sample form on the same instrument under the same experimental conditions results in two of the variables, K and λ, being constant.…”

“…Typically an enhancement of 10's to 100's is achieved with multipass approach. Increasing Raman light collection efficiency by specially designed optics [4] and utilizing higher gas pressure [5] also helped to raise detected Raman signals.…”