1. Real World: Determination of Calcium in Milk
By Delaney Caudill, Ethan Nichols, and Katie Vautier

2. Background Methods Considered Ion Selective Electrode Method
Trichloroacetic Acid Filtrate Method
Use of this acid as a protein precipitator to determine calcium content
Complexometric Titrations
A volumetric analysis in which a formation of a colored complex is used to indicate the end point of a titration

3. Purpose
Determine and compare the calcium content via a complexometric titration to listed values of different types of milk
Compare two different indicators

4. Procedure #1: Patton-Reeder
Dry EDTA at 80°C overnight
Make 750mL of M EDTA
Combine 10mL of sample, 40mL distilled water, and 4mL of 8M sodium hydroxide solution into an Erlenmeyer flask
Add 0.1g of Patton-Reeder indicator
Titrate w/ EDTA solution

5. Data Whole Milk Trial mL EDTA added Grams Ca2+ 1 9.72 0.013276 2 9.47 3
9.21 4
9.39
Avg.

6. % Difference Fat free milk: 5.1% 1% milk: 2.5% 2% milk: 2.0%
Whole milk: 6.2%
Calcium Fortified: 9.0%

7. Before Titration

8. After Titration

9. Color Change?

10. Procedure #2: Eriochrome Black T
Add 3mL of milk and 5mL ammonia buffer in a 250mL Erlenmeyer flask
Calibrate a pH meter and measure pH of each sample (needs to be 10)
Add 0.03g of indicator
Titrate with EDTA

11. Data Whole Milk Trial mL EDTA added Grams Ca2+ 1 5.10 0.0069659 2 4.48 3
4.41 4
4.50
Avg.

12. Results Whole milk: 54.1% Makes sense due to different indicator (EBT)
pH of sample was 10
pH had effect on sample?

13. Procedure #3: Eriochrome Black T
Same as procedure #1 except used different indicator: Eriochrome Black T

14. Data & Results No quantitative data
No color change due to the solution having a pH between 12 and 14
Eriochrome Black T indicates a color change at a pH of 10

15. No Color Change

16. Theoretical Grams of Ca per Serving
Based on a 2,000 calorie diet, daily calcium intake should be 1,100mg
Each milk carton claims it contains 30% of daily calcium intake

17. Example Calculations Grams Ca2+ in a serving of milk Ex. Whole Milk
Percent Difference

18. Sources of Error INDICATORS! Different people titrated samples
Subjective color change
Different people titrated samples
Reading the buret
Wait for precipitate to come out of solution to ‘remove’ magnesium oxide

19. Future Work Investigate different indicators
Change pH of samples to use Eriochrome Black T indicator by changing molarity of NaOH
Try other calcium supplements such as vitamins or orange juice

20. Conclusion Successful experiment
Efficient method: complexometric titration
Low percent differences
Necessary to order Patton Reeder since Eriochrome Black T yielded higher percent difference

21. References
Harris, Daniel C. Quantitative Chemical Analysis, 8th ed.; W.H. Freeman and Company: New York, 2010, page 240.

22. Special Thanks Dr. Peterman Melissa, Kate, Pat, and Kiersten
Professor Mowery

23. Questions?