Preparation of tea samples
1. Weigh ~ 0.5xxx g of leaf tea sample in two 100-ml beakers. Record the sample weights.
2. Transfer tea leaves in one beaker into a mortar. Use a pestle to crush the tea leaves.
Weigh the crushed tea leaves again in a 100-ml beaker. Record the weight.
3. Pour 50 ml of boiled water into each beaker. Infuse the leaf tea samples for 5 min.
4. Filter each tea solution through a filter paper into a 50-ml volumetric flask. Cool to room
temperature and adjust the volume to the mark with purified water.
5. Filter the sample solutions through syringe filter with 0.2 m nylon membrane.