The Influence of Experimental Conditions in Quantitative Analysis of Powdered Samples by Fourier Transform Infrared Photoacoustic Spectroscopy

Authors: Highfield, J. G.; Moffat, J. B.

Source: Applied Spectroscopy, Volume 39, Issue 3, Pages 377-562 (May/June 1985) , pp. 550-552(3)

Publisher: Society for Applied Spectroscopy

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Abstract:

Photoacoustic Spectroscopy (PAS) is now well-established as a useful technique for obtaining optical absorption spectra from strongly scattering and/or opaque materials which are difficult to study by conventional photometric methods. However, its quantitative application to solids in the UV-visible region has been somewhat restricted by the phenomenon of photoacoustic (PA) signal saturation, in which the intensity of the stronger bands in the spectrum becomes insensitive to changes in analyte concentration. By comparison, with the recent advent of Fourier Transform Infrared Photoacoustic Spectroscopy (FT-IR/PAS), this problem is expected to be much less serious in view of the low absorptivities characteristic of IR bands. Indeed, recent work in our laboratory has shown that when NH3 is sorbed stepwise into the bulk of 12-tungstophosphoric acid, H3PW12O40, the base is quantitatively converted to NH4 + ion, and the calibration curve of the analyte peak area (standardized against a reference band of the substrate) vs. analyte concentration is virtually linear up to stoichiometric loading. With the use of this method, several salts of the parent acid were found to exist in partial (Brønsted) acid form, and adjusted molecular formulae thus calculated were consistent with those obtained in dependently by elemental analysis.

Keywords: Infrared Photoacoustic Spectroscopy; Quantitative analysis; Signal saturation

Document Type: Short Communication

DOI: http://dx.doi.org/10.1366/0003702854248683

Affiliations: Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada

Publication date: May 1, 1985

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