A MATLAB Application for Calculation of Cell Pathlength in Absorption Transmission Infrared Spectroscopy

Fourier transform infrared spectroscopy is an established technique for the qualitative determination of organic structure. Absorption infrared spectroscopy can be employed quantitatively using Beer’s law. However, reliable quantitative analysis requires that the pathlength is known within 1%. Pathlengths based on nominal spacer thickness are not sufficient for accurate work due to variances in cell assembly and thermal expansion. The “interference pattern” method provides an accurate determination of cell pathlength but requires plotting of empty cell spectra and counting of the fringes. This work provides a MATLAB® application with a graphical user interface implementing an interactive plot where the user selects the spectral region for the calculation. Then the program automatically computes the cell pathlength providing a rapid determination of pathlength for practitioners.

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