Endoscopic Fourier-transform infrared spectroscopy through a fiber microprobe.

Fourier-transform infrared spectroscopy (FTIR) is a powerful analytical method not only for the chemical identification of solid, liquid, and gas species but also for the quantification of their concentration. However, the chemical quantification capability of FTIR is significantly hindered when the analyte is surrounded by a strong IR absorbing medium, such as liquid solutions. To overcome this limit, here we develop an IR fiber microprobe that can be inserted into a liquid medium and obtain full FTIR spectra at points of interest.