Muhammad Roy Asrori (Universitas Negeri Malang, Indonesia)
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Abstract: This study aims to determine the spin-lattice (T1) relaxation times of protons in ascorbic acid dissolved in deuterium oxide (D2O) to evaluate how molecular dynamics are influenced by varying solution concentrations. Nuclear Magnetic Resonance (NMR) T1 analyses were conducted on in-house prepared samples at a controlled temperature of 308.0 K. Data processing and fitting were performed using Bruker TopSpin and Dynamics Center software (version 2.8.4) , calculating relaxation times with the function f(t) = Io [1a*exp (-t/T1)]. Analysis of the first sample (1 mg in 1 mL D₂O) revealed T1 relaxation times of 1.09 s at 4.015 ppm and 0.958 s at 3.941 ppm. A second, more concentrated sample (10 mg in 1 mL D₂O) exhibited a broader range of proton signals, with downfield peaks showing longer relaxation times of 2.83 s at 5.184 ppm, 5.30 s at 4.311 ppm, and 2.86 s at 4.230 ppm. Conversely, other peaks in this higher-concentration sample demonstrated shorter T1 times, measuring 0.522 s at 4.074 ppm, 1.20 s at 4.022 ppm, and 1.03 s at 3.933 ppm. These results indicate that the T1 relaxation times of ascorbic acid in D2O at 308.0 K vary significantly, ranging from 0.522 s to 5.30 s depending on the specific proton environment, and suggest that an increase in concentration may influence intermolecular interactions—such as hydrogen bonding or molecular crowding—thereby altering the degrees of local mobility and relaxation mechanisms across the molecule.
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