Infrared spectroscopy baseline corrections

In other cases, a baseline corrected peak height for a particular absorber may be employed as a term in the equation. In such a case, the wavelength difference on either side of a peak maximum will affect the contribution of that complex term. That increment or gap, in fact, under such circumstances becomes a part of the calibration. It is as important a contribution to the calibration as the coefficients on the wavelength terms. In this correlation spectroscopy, classical band assignments are not always possible. Little specific near-infrared literature exists in advance of most applications and it is not always possible to predict which wavelengths will produce the best linearity and the best sensitivity for a given analytical problem. In the empirical approach a variety of statistical treatments have been attempted. By far the most... 

Figure 3.4 An example of a baseline correction. From Stuart, B Modem Infrared Spectroscopy, ACOL Series, WUey, Chichester, UK, 1996. University of Greenwich, and reproduced by permission of the University of Greenwich.

The value of computing derivative spectra to correct for non-linear baseline signals is frequently exploited in reflectance spectrometry. Rapid measurement of the chemical composition of materials and products by diffuse reflectance spectroscopy in the near-infrared (NIR) region (800-2600 nm) is routine in many industries. Because most bulk materials are not transparent the mode of measurement is generally reflectance. For powder samples the intensity of... 

Sample characterization. Fourier-transform infrared (FTIR) spectroscopy in ATR mode was used to monitor the geopolymerization. FTIR spectra were obtained using a ThermoFisher Scientific Nicolet 380 infrared spectrometer. The IR spectra were gathered over a wavenumber range of 400 to 4000 cm with a resolution of 4 cm To follow the evolution of the involved bonds in time, a software was used to acquire a spectrum every 10 min for 13 hours. The atmospheric CO2 contribution was removed with a straight line between 2400 and 2280 cm To allow comparisons of spectra, they were corrected using baseline and normalized. 

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