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Multiple path length mid-infrared spectra of liquids obtained by using a modified button sample holder
Jaspreet Singh1, Robert L White1
1Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA. rlwhite@ou.edu.
Analytical Methods : Advancing Methods and Applications
|April 13, 2022
Summary
This study introduces a modified mesh button sample holder for infrared spectroscopy. It reveals how varied absorption path lengths affect spectral data, enabling quantitative analysis with consistent sample volumes.
Area of Science:
- Analytical Chemistry
- Spectroscopy
- Materials Science
Background:
- Traditional transmission cells in infrared spectroscopy offer a single path length for radiation.
- This limits the analysis of samples with high absorptivity or complex overlapping bands.
- A novel sample holder is needed to overcome these limitations.
Purpose of the Study:
- To characterize a modified mesh button sample holder for infrared spectroscopy.
- To investigate the impact of multiple absorption path lengths on spectral data.
- To assess the utility of this holder for quantitative analysis.
Main Methods:
- Utilizing a modified stainless-steel mesh button sample holder.
- Examining the effects of varying liquid volumes on absorption path lengths.
- Analyzing infrared spectra obtained from the mesh button holder.
Main Results:
- Reflections within the mesh create a distribution of absorption path lengths.
- Higher absorptivity bands are measured with shorter effective path lengths.
- Overlapping band shapes are preserved in spectral regions that would be opaque in transmission.
- Absorbance is proportional to concentration with constant sample volumes, despite Beer's law inapplicability.
Conclusions:
- The modified mesh button holder provides variable, reproducible absorption path lengths.
- Spectral data interpretation requires consideration of wavenumber-dependent effective path lengths.
- This method facilitates quantitative infrared spectroscopic analysis, especially for challenging samples.
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