We report experimental results concerning the detection of 2,4-dinitrophenol, under its free form or coupled to human serum albumin using Fourier transform infrared spectroscopy-based sensors. Competitive immunoreactions were carried out using several anti-dinitrophenol monoclonal antibodies. Comparison with enzyme-linked immunosorbent assays in competition is given for standard operating conditions. FTIR detection limits are comparable to those obtained by ELISA. The limits of detection are about 5-15 ng/mL for the coupled DNP. Using the LO-DNP61 antibody, a detection limit of congruent with 5 ng/mL was also estimated for the free DNP molecules but is much higher for the other antibodies.