Instrumental Resolution Considerations for Fourier Transform Infrared Gas-Phase Spectroscopy

Abstract

Instrumental resolution has a significant effect on the performance of Fourier transform infrared (FT-IR) spectrometers used for gasphase analysis. Low-resolution FT-IR spectroscopy offers some valuable advantages compared with the traditional high-resolution FT-IR gas-phase spectroscopy, especially in nonlaboratory environments. First, high signal-to-noise ratio (SNR) spectra can be acquired in field conditions without the use of traditional liquid nitrogen-cooled detectors. Second, the dynamic range for quantitative analysis is larger for low-resolution spectroscopy than for high-resolution due to the lower absorbance values and lower noise levels. Third, spectral analysis speed is increased and data storage requirements are substantially reduced. The purpose of this study was to investigate the effect of instrumental resolution on FT-IR gas-phase analysis. The effects of spectral resolution on sensitivity, selectivity, accuracy, precision, spectral overlap, dynamic range, and nonlinearity are separately discussed.

Portable combination of Fourier transform infrared spectroscopy and differential mobility spectrometry for advanced vapor phase analysis

“…While the increased number of averaged scans should have led to a lower noise level, 42 it is known that at higher spectral resolution, the noise level is elevated. 43 Therefore, the noise increasing impact of the increased resolution in the IR(300)-GC-DMS setup obviously outweighed the noise decreasing impact of the increased number of averaged scans (assuming that the flow rate did not have a significant influence on the noise level). Contradictory to Jaakkola et al , 43 the SNR for the IR(300)-GC-DMS setup was increased vs. the other two setups (Table 1).…”

“…43 Therefore, the noise increasing impact of the increased resolution in the IR(300)-GC-DMS setup obviously outweighed the noise decreasing impact of the increased number of averaged scans (assuming that the flow rate did not have a significant influence on the noise level). Contradictory to Jaakkola et al , 43 the SNR for the IR(300)-GC-DMS setup was increased vs. the other two setups (Table 1). It was expected that at increased resolution, the signal intensity and the noise increase in a way that the SNR…”

“…Furthermore, the rather moderate spectral resolution may lead to non-linearities, as well. 43 From an analytical point of view, quantification of thus obtained data is readily enabled via a non-linear curve fit. Like in Fig.…”

Impurities in hydride gases part 1: Investigation of trace moisture in the liquid and vapor phase of ultra-pure ammonia by FTIR spectroscopy

“…A second order polynomial correction was used to account for deviations from Beer's law, which are assumed to be a result of the low spectral resolution of 4 cm -1 used for all measurements. 17 The stability of the moisture readings at low concentration gives a limit of detection (LOD) of <45 ppb based on 3s calculated from signal/ noise ratios. This number, however, does not represent the absolute accuracy of the method based on the calibration data used, and a method detection limit (MDL) is preferred.…”

Improving the robustness of multivariate calibration models for the determination of glucose by near-infrared spectroscopy

“…When the beam entering the interferometer is restricted in diameter such that aperture broadening is not limiting, the instrumental resolution is determined by the maximum retardation of the interferogram. 129 Increasing resolution thus requires sampling a longer interferogram. Because the spectral bandwidth is constant and noise is typically spread evenly throughout the interferogram, increasing resolution also increases the noise level in the computed single-beam spectrum by a factor of 2 ½ for each factor of 2 increase in the interferogram length.…”