Finding a single optimal pathlength for liquid phase spectroscopy of a high absorbing matrix is hardly possible in most cases, due to the varied background absorbance across different wavelengths. [1][2] In this work, we propose a multi-pathlength transmission cell in combination with a high performing external-cavity quantum cascade laser (EC-QCL). This allows us to measure samples simultaneously at different pathlengths to determine the most optimal sample thickness for each characteristic band of the solute. Ultimately, we anticipate our setup to increase the signal-to-noise ratio for measurements of solutes (i.e., proteins) in water compared to conventional infrared (IR) spectrometers.