Caffeic Acid Based Polyurethane Membrane Modified Screen-Printed Electrodes and Their Application for the Simultaneous Determination of Melatonin and Serotonin

Caffeic acid (CA) based polyurethane (PU) films were synthesized and characterized for the simultaneous determination of melatonin (MT) and serotonin (5-HT). The CA based PUs were synthesized using a polyol mixture of 4,4'-diisocyanodiphenylmethane (MPI), polyethylene glycol-200 (PEG), and CA. The PEG–CA monomer units in the polyol were varied in molar ratios of 99:1, 97:3, 95:5, and 90:10. The synthesized PUs were characterized by FTIR spectroscopy and thermal analysis. These CA based PU films were coated onto screen-printed carbon electrodes (SPCEs) with varying thicknesses and used for the simultaneous determination of MT and 5-HT. Electrochemical responses of MT and 5-HT were evaluated using differential pulse voltammetry. The limit of detection and correlation coefficient for MT were 280 µM and 0.9797, respectively, while for 5-HT, the detection was 150 µM with a correlation coefficient of 0.9690. The precision, expressed as the relative standard deviation was 2.633% for MT and 4.668% for 5-HT. These findings suggest that CA based PU-modified electrodes hold potential in medical and biomedical applications.