Comparison of gas chromatography/Fourier transform infrared spectrometric Gram-Schmidt reconstructions from different interferometers

Abstract

The results of an experimental comparison of Gram-Schmidt GC/FT-IR chromatogram reconstructions as calculated from data measured on two different Interferometers áre presented. The comparison was made using the same sample, GC column, separation conditions, transfer lines, light pipe, detector, and detector optics. Only the Interferometers, source, source optics, and data systems were varied. It Is determined that the optimum vector displacement Is dependent upon the stability of the Interferometer used, but In general the centerburst should be just outside the sampled region.

Gram—Schmidt Orthogonalization for Rapid Reconstructions of Fourier Transform Infrared Spectroscopic Imaging Data

“…Considerable discussion exists on the use of an appropriate region, or ''window'', of the interferogram for calculating the G-S basis set and intensity. 10 In particular, the size and position of this window may be critical to the predictive performance of the technique. Various studies utilize regions away from the centerburst, 10,11 while others stress the inclusion of the centerburst.…”

“…10 In particular, the size and position of this window may be critical to the predictive performance of the technique. Various studies utilize regions away from the centerburst, 10,11 while others stress the inclusion of the centerburst. The appropriate window for an experiment, which is chosen to maximize the signal-to-noise ratio (SNR), depends on the analytes and instrumentation 10,11 and is usually chosen tens of points away from the centerburst.…”

“…Various studies utilize regions away from the centerburst, 10,11 while others stress the inclusion of the centerburst. The appropriate window for an experiment, which is chosen to maximize the signal-to-noise ratio (SNR), depends on the analytes and instrumentation 10,11 and is usually chosen tens of points away from the centerburst. 7,11 However, the region of the interferogram close to the centerburst, indicative of the transmitted intensity over the entire spectral bandwidth, is sensitive to both the total sample absorption and scattering effects.…”

“…This advantage is not available for G-S profiles from macroscopic IR data in which the inclusion of the centerburst does not appreciably affect the SNR of the G-S profile. 10 It must be noted that the image contrast resulting from including the centerburst originates from both absorption and scattering effects due to refractive index mismatches in a heterogeneous sample. Hence, we recommend excluding the centerburst when routinely performing G-S orthogonalization on heterogeneous samples in which spatial chemical differences are to be determined and including it only when any difference is critical to the task, as for example, in quality control applications.…”

FOURIER TRANSFORM INFRARED VIBRATIONAL SPECTROSCOPIC IMAGING: Integrating Microscopy and Molecular Recognition

“…Considerable discussion exists on the use of an appropriate region, or window, of the interferogram for calculating the G-S basis set and intensity (87). In particular, the size and position of this window may be critical to the predictive performance of the technique (87,88) and is usually chosen away from the centerburst (84,88). In imaging data sets, the region of the interferogram close to the centerburst is also indicative of the transmitted intensity over the entire spectral bandwidth.…”