A new complex was prepared from nicotinic acid and terbium chloride (NIC-Tb) and characterized using sophisticated techniques (CHN, FT-IR, UV ,TGA and DTA thermal techniques). The prepared complex determined the ascorbic acid concentration in the pharmaceutical ingredient. The luminescence intensity of the probe decreases as the concentrations of the ascorbic acid increase. At different temperatures, Stern–Volmer studies indicate a dynamic quenching mechanism. The calculation of the thermodynamic parameters ((∆Sº, ∆Hº, and ∆Gº) and binding constants (K) of the Ascorbic acid-probe complex interaction revealed a spontaneous hydrophobic interaction. The specified range was found to be in the range of 1×10-5 – 1×10-4 M. The recovery values were 97.6-98.89. The fluorescence probe's quenching mechanism was collisional (dynamic), as demonstrated by the experiments. The interaction by electrostatic forces is shown by the thermodynamic parameter values. The limit of detection was found to be equal to 1.9 µM and the quantitation limit was 28 mM.