Journal : Applied Spectroscopy , vol. 60 , p. 1029–1039–11 , 2006
International Standard Numbers
Printed : 0003-7028
Electronic : 1943-3530
Publication type : Academic article
Issue : 9
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Fourier transform infrared (FT-IR) spectroscopy is a valuable technique for characterization of biological samples, providing a detailed fingerprint of the major chemical constituents. However, water vapor and CO2 in the beam path often cause interferences in the spectra, which can hamper the data analysis and interpretation of results. In this paper we present a new method for removal of the spectral contributions due to atmospheric water and CO2 from attenuated total reflection (ATR)-FT-IR spectra. In the IR spectrum, four separate wavenumber regions were defined, each containing an absorption band from either water vapor or CO2. From two calibration data sets, gas model spectra were estimated in each of the four spectral regions, and these model spectra were applied for correction of gas absorptions in two independent test sets (spectra of aqueous solutions and a yeast biofilm (C albicans) growing on an ATR crystal, respectively). The amounts of the atmospheric gases as expressed by the model spectra were estimated by regression, using second-derivative transformed spectra, and the estimated gas spectra could subsequently be subtracted from the sample spectra. For spectra of the growing yeast biofilm, the gas correction revealed otherwise hidden variations of relevance for modeling the growth dynamics. As the presented method improved the interpretation of the principle component analysis (PCA) models, it has proven to be a valuable tool for filtering atmospheric variation in ATR-FT-IR spectra.