Comparison of methods of extraction caffeine from tea

Tea is very important for Chinese people.The tea production and sales in China is in the leading place of the world.In this experiment,green tea was used as raw material,caffeine was extracted by microwave-assisted extraction method.The impact factors was studied by L16(45)orthogonal experiment and used the traditional Soxhlet extraction as the control.The experiment results showed that the best extraction conditions were as follows:microwave power 0.2kW,extraction agent 80%(v/v)ethanol,solid-liquid ratio of 1:16(m/V),extraction time of microwave irradiation 9 min(gap-type extract),caffeine yield was 217.5mg/10g,50.2%higher than Soxhlet extraction which caffeine yield was 144.8mg/10g after 6 hours extration.The highest yield was 221.8mg/10g which was 49.1% higher than the highest Soxhlet extraction's of 148.8mg/10g.The quality indicators of caffeine obtained by microwave method such as purity,appearance and stability etc.,were remarkable superior to Soxhlet method’s.This provides the basic information for further studies in the future.