Kinetics of glucose mutarotation assessed by an equal-amplitude paired polarized heterodyne polarimeter

A dual-frequency equal-amplitude paired polarization heterodyne Polarimeter (DEPHP) was set up in order to precisely measure the mutarotation rate constants of D-glucose in tridistilled water. The DEPHP is based on a balanced detector detection scheme for measurement of the optical rotation angle of D-glucose/water solution during the conversion process between α-D-glucose and β-D-glucose while in a nonequilibrium state. The DEPHP can perform shot-noise-limited detection, so that the total, optical rotation angle together with the mutarotation rate constants of α-D-glucose and β-D-glucose conversion can be measured with high sensitivity. In this experiment, the sensitivity of the optical rotation angle measurement was 8.3 × 10 ^-5 deg/ cm, while the total (k), forward (k₁ and reverse (k₂) mutarotation rate constants of D-glucose were found to be k = 7.67 × 10^-5 s^-1 k₁ = 2.76 × 10 ^-5 s^-1, and k₂ = 4.91 × 10^-5 s^-1 respectively, in tridistilled water. Moreover, using the DEPHP, we can measure the specific rotation angles of α-D-glucose and β-D-glucose in water at 632.8 nm. They were 105° and 12°, respectively. Finally, the detection sensitivity of the DEPHP system is also discussed.