所以先选DCPIP做vitamin C既indicator的~~~ chemical reaction 如下~~~ DCPIP (blue) + H+ ---> DCPIPH (pink) DCPIPH (pink) + VitC ---> DCPIPH2 (colourless) C6H8O6 + C12H7NCl2O2 ---> C6H6O6 + C12H9NCl2O2 详请可以睇下维基点讲嘅。可惜只有英文~~~ 希望帮到你啦=...