Nalyzing the Vitamin C content of soft fruit drinks

A manufacturer of a soft fruit drinks has produced a new range of drinks. You are asked to demonstrate which, if any, contain more vitamin c than the previous range of drinks.
You are provided with:
a? Blue dye.
a? A solution containing a known amount of vitamin c.
a? A selection of old products a a lemon, orange and blackcurrant drink.
a? A selection of new products a a lemon, orange and blackcurrant drink.