Quantifying Vitamin C Levels in Flavorite’s “Grapefruit Juice”

Analysis of Vitamin C in Juice Product, Data in Slides 12-14

(1) Molarity of Standard Ascorbic Acid Solution

Standard Solution of AA =

(0.05 (g AA/100mL) x 1000mL)/176.1(g AA/mol) = 2.84 x 10-3 M

(2) Molarity of DCP Solution

Standard Solution of DCP =

(2.84×10-5mol DCP/33.57mL DCP) x 1000mL = 8.50×10-4 M in Trial 1

(3) Mass of Ascorbic Acid Titrated in Juice Sample

Ascorbic Acid Mass Titrated in Juice =

((8.5×10-4) mol DCP/1000mL) x (13.61 mL DCP) x (176.1 g AA/mol) x (1000mg/g)) / (5mL juice) = 0.42 mg/mL of Ascorbic Acid in Trial 1

Analysis

This lab focused on determining the amount of Vitamin C in 5 mL of Flavorite’s grapefruit juice by means of oxidation-reduction titrimetry. Our calculations from three trials infer an average of 2.32 milligrams per five mL sample of grapefruit juice. It is important to evaluate our experimental value with the container’s RDA value of 130% in eight ounces, which alleges juice should have 1.63 milligrams per five mL sample. Comparing the experimental value shows a 42% discrepancy, which is not unexpected. In the experiment there were many variables that could have caused slight deviation from the real value: we used many different measurements and reagents to calculate the Vitamin C quantity. On the other hand, we have a handful of data to support our answer; it is too hard to tell if Flavorite’s RDA values are more accurate.

Average Vitamin C in Flavorite Grapefruit Juice: 0.464 mg/ml

 

 

1. Initial Data

Weighing Paper (g)

0.42

Vitamin C solution
with ascorbic acid

0.47

Volume: 100mL
Ascorbic acid (g)

0.05

Molarity: 2.84×10-3M
2. Standardizing the DCP Solution
Trials

1

2

3

Volume of Vitamin C titrated (mL)

10

10

10

Initial buret reading (mL)

0

0

0

Final buret reading (mL)

33.57

37.94

31.1

Moles of Vitamin C titrated 2.84×10-5 2.84×10-5 2.84×10-5
DCP Solution (M) 8.5×10-4 8.6×10-4 9.13×10-4
DCP Solution (M)average 8.77×10-4
3. Analyzing Vitamin C in Juice Sample
Juice Tested: Flavorite Grapefruit
Trials

1

2

3

Volume of juice titrated (mL)

5

5

5

Initial buret reading (mL)

0

13.61

28.62

Final buret reading (mL)

13.61

28.62

45.11

Volume of DCP titrated (mL)

13.61

15.01

16.49

DCP required (mol) 1.19×10-5 1.32×10-5 1.45×10-5
Mass of Vitamin C titrated (mg)

2.1

2.32

2.55

Quanitiy of Vitamin C (mg/mL)

0.42

0.464

0.51