Authors: Bruun, Susanne W.¹; Kohler, Achim²; Adt, Isabelle³; Sockalingum, Ganesh D.³; Manfait, Michel³; Martens, Harald⁴

Source: Applied Spectroscopy, Volume 60, Issue 9, Pages 220A-236A and 951-1095 (September 2006) , pp. 1029-1039(11)

Publisher: Society for Applied Spectroscopy

Abstract:

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.

Keywords: FOURIER TRANSFORM INFRARED SPECTROSCOPY; FT-IR SPECTROSCOPY; ATTENUATED TOTAL REFLECTION; ATR; ATMOSPHERIC CORRECTION; ATMOSPHERIC ABSORPTIONS; PRINCIPAL COMPONENT ANALYSIS; PCA

Document Type: Research article

DOI: http://dx.doi.org/10.1366/000370206778397371

Affiliations: 1: Biochemistry and Nutrition Group, BioCentrum-DTU, Technical University of Denmark, building 224, Søltofts Plads, DK-2800 Kgs. Lyngby, Denmark 2: Center for Biospectroscopy and Data Modelling, Matforsk, Norwegian Food Research Institute, N-1430 Aas, Norway; Unité de Sensométrie et de Chimiométrie, ENITIAA, BP 82225, 44322 Nantes Cedex 3, France 3: Unité MéDIAN CNRS UMR 6142, UFR Pharmacie, IFR 53, Université de Reims Champagne Ardenne, 51 rue Cognacq-Jay, 51096 Reims Cedex, France 4: Center for Biospectroscopy and Data Modelling, Matforsk, Norwegian Food Research Institute, N-1430 Aas, Norway; CIGENE/IKBM, Norwegian University of Life Sciences, N-1430 Aas, Norway; The Royal Veterinary & Agricultural University, 1870 Frederiksberg C, Denmark

Publication date: 2006-09-01

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