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

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

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

Procedure #1: Patton-Reeder Dry EDTA at 80°C overnight Make 750mL of 0.03408M 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

Data Whole Milk Trial mL EDTA added Grams Ca2+ 1 9.72 0.013276 2 9.47 0.012935 3 9.21 0.012580 4 9.39 0.012825 Avg. ---------- 0.012904

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

Before Titration

After Titration

Color Change?

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

Data Whole Milk Trial mL EDTA added Grams Ca2+ 1 5.10 0.0069659 2 4.48 0.0061190 3 4.41 0.0060234 4 4.50 0.0061464 Avg. ---------- 0.0063137

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

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

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

No Color Change

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

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

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

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

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

References Harris, Daniel C. Quantitative Chemical Analysis, 8th ed.; W.H. Freeman and Company: New York, 2010, page 240. http://www.chemteach.ac.nz/invesigations/documents/calcium.pdf http://www.jbc.org/content/90/3/747.full.pdf

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

Questions?