Measuring the content of Vitamin C in fruit juice

Independent: fruit juice

Dependent: Vol. juice decolourise 1cm3 of DCPIP

Control: Temp. Conc. DCPIP solution (1%) Shake tube same number times Same end point colour (until blue colour of DCPIP disappears)

Method: Pipette 1cm3 blue DCPIP into test tube. Using burette/ accurate pipette/syringe, add 1% vitamin C solution drop by drop, while shaking tube gently after each drop, until blue colour just disappears. Record volume solution needed to decolourise the DCPIP. Repeat further 2 times & calculate mean result. Repeat procedure with different juices.

Calculation:1cm3 of 1% vitamin solution contains 10mg Vitamin C, mass 1cm3 = 10mg x volume of 1% vitamin C decolourise 1cm3 of DCPIP. Mass sample = mass vitamin C decolourise 1cm3 DCPIP/ volume sample to decolourise 1cm3 DCPIP

Evaluation issues: Difficult control temp. Amount shaking (too much adds O2, slightly restore DCPIP blue) End point difficult judge when blue colour disappears especially in high coloured juices.

Method