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Proceedings Paper

Optimization of quantitative infrared analysis
Author(s): Richard W. Duerst; W. E. Breneman; Rebecca M. Dittmar; Richard E. Drugge; Jim E. Gagnon; Robert A. Pranis; Colleen K. Spicer; William L. Stebbings; J. W. Westberg; Marilyn D. Duerst
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Paper Abstract

A number of industrial processes, especially quality assurance procedures, accept information on relative quantities of components in mixtures, whenever absolute values for the quantitative analysis are unavailable. These relative quantities may be determined from infrared intensity ratios even though known standards are unavailable. Repeatability [vs precisionhl in quantitative analysis is a critical parameter for meaningful results. In any given analysis, multiple runs provide "answers" with a certain standard deviation. Obviously, the lower the standard deviation, the better the precision. In attempting to minimize the standard deviation and thus improve precision, we need to delineate which contributing factors we have control over (such as sample preparation techniques, data analysis methodology) and which factors we have little control over (environmental and instrument noise, for example). For a given set of conditions, the best instrumental precision achievable on an IR instrument should be determinable. Traditionally, the term "signal-to-noise" (S/N) has been used for a single spectrum, realizing that S/N improves with an increase in number of scans coadded for generation of that single spectrum. However, the S/N ratio does not directly reflect the precision achievable for an absorbing band. We prefer to use the phrase "maximum achievable instrument precision" (MAIP), which is equivalent to the minimum relative standard deviation for a given peak (either height or area) in spectra. For a specific analysis, the analyst should have in mind the desired precision. Only if the desired precision is less than the MA1P will the analysis be feasible. Once the MAIP is established, other experimental procedures may be modified to improve the analytical precision, if it is below that which is expected (the MAIP).

Paper Details

Date Published: 31 January 1994
PDF: 2 pages
Proc. SPIE 2089, 9th International Conference on Fourier Transform Spectroscopy, (31 January 1994); doi: 10.1117/12.166724
Show Author Affiliations
Richard W. Duerst, 3M Co. (United States)
W. E. Breneman, 3M Co. (United States)
Rebecca M. Dittmar, 3M Co. (United States)
Richard E. Drugge, 3M Co. (United States)
Jim E. Gagnon, 3M Co. (United States)
Robert A. Pranis, 3M Co. (United States)
Colleen K. Spicer, 3M Co. (United States)
William L. Stebbings, 3M Co. (United States)
J. W. Westberg, 3M Co. (United States)
Marilyn D. Duerst, Univ. of Wisconsin/River Falls (United States)

Published in SPIE Proceedings Vol. 2089:
9th International Conference on Fourier Transform Spectroscopy
John E. Bertie; Hal Wieser, Editor(s)

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