The Surface-Specificity of IRRAS in Studying Soluble Organic Acids: An Interview with Alexandra Deal

Infrared reflection absorption spectroscopy (IRRAS) is widely employed for analyzing molecules on surfaces, especially water, with applications in atmospheric chemistry and food science. However, concerns exist about its surface-specificity, particularly when examining soluble surfactants in aqueous solutions.

Alexandra Deal, who currently works at Lawrence Berkeley National Laboratory, explored the surface-specificity of IRRAS in soluble organic acids beneath monolayers of insoluble surfactants while she was a graduate research assistant at the University of Colorado, Boulder. She published her findings in Applied Spectroscopy (1). Spectroscopy spoke with Deal to learn more about her research and IRRAS as a technique.

Alexandra Deal of Lawrence Berkeley National Laboratory | Photo Credit: © Alexandra Deal

In this video interview, Deal responds to the following questions:

1. Can you provide more details about the debate surrounding the surface-specificity of IRRAS on aqueous solutions?
2. Your research paper mentions "subsurface effects" and the subtraction of contributions from insoluble surfactants in the spectra. Could you explain the methodology used to capture these subsurface effects and how it contributes to the understanding of surface-specificity in IRRAS?
3. The research demonstrates that IRRAS spectra of soluble organic acids are surface-specific. Could you elaborate on the key findings and how this conclusion was reached?
4. You mention a simplified model for reflections from "subsurface" layers. Could you describe this model and its role in interpreting the results of the study?
5. Would you describe how IRRAS might be used for measurements in the fields of atmospheric chemistry and food science?
6. What was unique about your study compared to previous studies? What conclusions should be taken from your study?

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Reference

(1) Deal, A. M. Infrared Reflection Absorption Spectroscopy (IRRAS) of Water-Soluble Surfactants: Is it Surface-Specific? Appl. Spectrosc. 2023, ASAP. DOI: 10.1177/00037028231200903