Quantitative approach to the sample contact problem in attenuated total reflection spectroscopy: Theoretical considerations
✍ Scribed by S.D. Stuchebryukov; V.M. Rudoy
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 472 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0924-2031
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✦ Synopsis
The problem of non-ideal contact between an internal reflection element (IRE) and a rough sample under study is considered. The influence of the width of the gap on the intensity of attenuated total reflection (ATR) spectra is quantitatively analysed and equations for the absorbance (A) are derived. It is shown that in many instances surface roughness reduces A as compared with the true (i.e., corresponding to ideal contact between IRE and sample) value (Aid) by a factor of 2-5. Quantitative ATR analysis is evidently impossible under such circumstances without regard to the influence of the air gap. To solve this problem, two approaches are developed. Both methods are based on the measurement of the A values followed by calculation of Aid quantities. The first approach is based on the measurement of spectra with two different polarizations and the second utilizes the ratio of A values obtained for the band under study and for the "internal standard" band. It is shown that relative errors in Aid determination are less than 5% for both methods.