Sugar Analysis in Tea using Optical Rotation and Refractive Index detection

Download PDF August 25, 2017

Introduction

An optical rotation detector can be used for selective detection of optically active materials.

The sugar in black and lemon teas were analyzed using a combination of optical rotation detector (OR) and refractive index detector (RI).

Figure 1 Chromatogram of a standard sample. Meso-erythritol is optically inactive and can only be detected by refractive index.

Figure 2 chromatograms of sugar-free black tea and lemon tea.

Jasco OR 2090
Jasco OR 2090

Figure 1. Chromatogram of a standard sample. 1. meso-Erythritol, 2. D-Xylose, 3. D-Fructose, 4. D-Glucose, 5. D-Sorbitol, 6. D-Sucrose

Figure 2, Limonene and Carvone have very similar UV spectra, but show differences in the IR. Co-elution in the chromatogram detected using UV as shown in figure 3 and 4 illustrates the inability of using UV to trigger fraction collection.

Figure 5 shows IR chromatograms at two different wave number ranges and the fractions collected using those chromatograms. A Carvone standard and Spearmint oil were separated using HPLC and fractions 1 and 2 were compared to confirm the separation and purity as seen in Figure 6.

Figure 2. Chromatogram of tea samples. 1. meso-Erythritol, 3. D-Fructose, 4. D-Glucose, 6. D-Sucrose

About the Author

Mr. Tamura is a member of the applications team with a specialty in vibrational spectroscopy and particularly Raman and IR Imaging. He is also one of our experts in gas analysis by FTIR.