Thesis Archive
The Effect of Temperature on the Measurement of Diffusion Coefficients and Antioxidant Activities of Ascorbic Acid Found in Guava Juice Using Cyclic Voltammetry (2015-2016)
Kurt Bryan A. Ang
Caridge M. Lee
Hans Maverick O. Yu
Abstract:
-Ascorbic acid is the most abundant antioxidant present in guava (Psidiumguajava L.). There had only been few studies concerning the determination of both the antioxidant activity and the diffusion coefficient of ascorbic acid in guava juice using cyclic voltammetry at varying temperatures. Thus, this study on the effect of temperature on the antioxidant activity and diffusion coefficient on ascorbic acid found in guava was determined using cyclic voltammetry. The temperature tested were at 15oC, 25oC, 36oC, and 45oC. Electrodes used in the experiment were glassy carbon as the working electrode, platinum wire as the counter electrode, and Ag/AgCl electrode as the reference electrode. The results showed that the peak currents of ascorbic acid in guava juice at 15oC, 25oC, 36oC, and 45oC were -0.5720, -0.5380, -0.5000, and -0.4760 μA, respectively. The antioxidant activity, in terms of concentration, at the said temperatures were found to be 0.3374, 0.3212, 0.3015, and 0.2899 mM, respectively. The diffusion coefficient of the ascorbic acid was obtained using the Randles-Sevcik equation at all given temperatures and the values were 2.1489 x10-5, 2.1711 x10-5, 2.2070 x10-5, and 2.2250 x10-5 cm2/s, respectively. It is concluded that at higher temperature, ascorbic acid in guava juice has a higher diffusion coefficient but lower antioxidant activity.
Adviser:
Dr. Nathaniel P. Dugos
Ms. Marylou Uy