Real World: Determination of Calcium in Milk

Real World: Determination of Calcium in MilkBy Delaney Caudill, Ethan Nichols, and Katie VautierBackgroundMethods ConsideredIon Selective Electrode MethodTrichloroacetic Acid Filtrate MethodUse of this acid as a protein precipitator to determine calcium contentComplexometric TitrationsA volumetric analysis in which a formation of a colored complex is used to indicate the end point of a titration

PurposeDetermine and compare the calcium content via a complexometric titration to listed values of different types of milkCompare two different indicatorsProcedure #1: Patton-ReederDry EDTA at 80C overnightMake 750mL of 0.03408M EDTACombine 10mL of sample, 40mL distilled water, and 4mL of 8M sodium hydroxide solution into an Erlenmeyer flaskAdd 0.1g of Patton-Reeder indicator Titrate w/ EDTA solutionDataTrialmL EDTA addedGrams Ca2+19.720.01327629.470.01293539.210.01258049.390.012825Avg.----------0.012904Whole Milk% DifferenceFat 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 TAdd 3mL of milk and 5mL ammonia buffer in a 250mL Erlenmeyer flaskCalibrate a pH meter and measure pH of each sample (needs to be 10)Add 0.03g of indicatorTitrate with EDTADataTrialmL EDTA addedGrams Ca2+15.100.006965924.480.006119034.410.006023444.500.0061464Avg.----------0.0063137Whole MilkResultsWhole milk: 54.1%Makes sense due to different indicator (EBT)pH of sample was 10pH had effect on sample?Procedure #3: Eriochrome Black TSame as procedure #1 except used different indicator: Eriochrome Black T

Data & ResultsNo quantitative dataNo color change due to the solution having a pH between 12 and 14Eriochrome Black T indicates a color change at a pH of 10No Color Change

Theoretical Grams of Ca per ServingBased on a 2,000 calorie diet, daily calcium intake should be 1,100mgEach milk carton claims it contains 30% of daily calcium intake

Example CalculationsGrams Ca2+ in a serving of milk

Ex. Whole Milk

Percent Difference

Ex. Whole Milk

Sources of ErrorINDICATORS!Subjective color changeDifferent people titrated samplesReading the buretWait for precipitate to come out of solution to remove magnesium oxideFuture WorkInvestigate different indicatorsChange pH of samples to use Eriochrome Black T indicator by changing molarity of NaOHTry other calcium supplements such as vitamins or orange juiceConclusionSuccessful experimentEfficient method: complexometric titrationLow percent differencesNecessary to order Patton Reeder since Eriochrome Black T yielded higher percent differenceReferencesHarris, 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.pdfhttp://www.jbc.org/content/90/3/747.full.pdfSpecial ThanksDr. PetermanMelissa, Kate, Pat, and KierstenProfessor MoweryQuestions?