Waveguide Absorption Spectroscopy of Bovine Serum Albumin in the Mid-Infrared Fingerprint Region

(5.3-10.0 μm) region of the MIR. GOS waveguides were shown to guide light up to a wavelength of 12.9 μm. The waveguide absorption spectrum of water, showing molecular bending vibrations, was obtained experimentally and compared with a theoretical model showing good agreement. Measurement of a concentration series of BSA protein in phosphate buffered saline (PBS) from 0.1 mg/mL to 100 mg/mL was performed on the waveguide using filter paper as a flow strip, and the amide I, II, and III peaks were observed and quantified.