Separaton of food colors

CHROMATOGRAPHY SEPARATION OF F. D. & C. FOOD COLORS IN M&M CANDIES (Revised: 1-24-93) INTRODUCTION Paper chromatography is an important separation technique that depends on differences in both absorption and solubility. A small amount of the mixture to be separated is placed close to the edge of a piece of chromatography paper. The edge of the paper is then immersed in a developing solution. As the developing solution ascends up the paper by capillary action, the components of the sample are carried along at different rates. To prevent evaporation of the developing solution, this process is carried out in a closed container. Each component of the mixture will move a definite distance on the paper in proportion to the distance that the solvent moves. This ratio, distance component moves (retention factor) Rf = __________________________ distance solution moves can be calculated for each component, to aid in identification. Retention factor values are dependent upon the paper, developing solution, and sample size. Candies, such as M & M's, contain FD&C (Food, Drug, and Cosmetic Act) dyes, sugars, and other organic and inorganic substances in their coatings. If the coating is dissolved in an acidic solution (white household vinegar), the FD&C dyes can be absorbed from the solution by wool. The dyes can then be released from the wool by placing it in an alkaline environment. This simplified equation represents the equilibrium involved: WOOL + DYE + H+ _ DYED WOOL+ A solution of household ammonia can be used to supply sufficient OH─ to reduce the concentration of the H+ and shift the equilibrium to the left which releases the dyes. PURPOSE In this experiment, you will extract the dyes in candy coatings using wool and then separate the dyes using the technique of paper chromatography. If samples containing known FD&C dyes are run as standards, it is possible to identify the dyes used in the candy coatings. Food colors provide a readily available source of known dye samples. Pure samples of food dyes can be obtained from CHROMATOGRAPHY Rainbow Colors, R.R. #1, Box 126D, Brookfield, MA. 01506. (Phone 508-867-6428) For $15.00 and $2.00 shipping, they will send you 2 gram samples of each of the seven food dyes. SAFETY AND PROCEDURAL CONSIDERATIONS 1. 2. Don't let the chromatography paper touch the sides of the beakers. Avoid touching the paper with your hands as much as possible. PRE-LAB QUESTIONS 1. 2. 3. 4. Develop a Vee diagram. What is the mobile phase in a paper chromatography investigation? What is the stationary phase in a paper chromatography investigation? What is meant by the term retention time? MATERIALS Equipment 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Substances Bunsen burner 1.clear household vinegar graduated cylinder 2. clear household ammonia 600 ml beaker 3. M & M's tooth picks or capillary tubes 4. FD&C dyes plastic wrap evaporating dish chromatography paper ring stand and wire gauze wool yarn (not acrylic) ultraviolet lamp 10 x 20 cm pieces of chromatography paper PROCEDURE Part A - CHROMATOGRAPHY OF F. D. & C DYES 1.Draw a pencil line 1 cm from the bottom of the long edge of each of the two 10 x 20 cm sheets of chromatography paper. Mark six or seven equally spaced positions along the pencil line (the first and last positions should be at least 1.5 cm from the edge of the paper). Use a tooth pick or a capillary tube to place a small spot of each of the concentrated FD&C dyes on the marked positions. Allow the sports to dry and spot them again in exactly the same positions to increase the amount of sample. CHROMATOGRAPHY 2.Cut the corners off the bottom of the paper (below the baseline). Staple the paper in a cylindrical shape. 3.Add 5the ml bottom of vinegar to acylinder. 600 ml beaker. Place thethe cylindrical paper the beaker with at of the Be careful that paper does not in touch the sides of the the spots beaker. Cover the beaker with plastic wrap and allow the chromatogram to develop until the developing solution is about 1 cm from the top of the paper. Remove the paper from the beaker, open it out, and lay it on a piece of paper towel to dry. Mark the solvent line with a pencil, all the way across the paper. It is important you do this NOW. After the paper has dried, you won't be able to see the solvent line! Save for part B Part B - CHROMATOGRAPHY OF M&M DYES 4.Select two different colored M&M's (two M&M's of each color). Keeping the colors separated, place the M&M's in separate 100 ml beakers. Add enough household vinegar to cover the top of the M&M's. Heat very gently until the colored coating dissolves. Vigorous heating will place too many unwanted solids in the solutions. 5.Carefully decant the solutions which now contains the FD&C dyes, some sugar, etc into another 100 ml beaker. Avoid transferring the sediment. 6.To extract the dyes, add the prepared length (10-15 cm) of woolen yarn to the 100 ml beakers containing the dyes. Heat the beakers gently for about five minutes. Stir constantly while heating. 7.Take the wool out of the beaker and rinse the wool a little with tap water. 8.In a clean beaker, place the wool with about 5 ml of household ammonia. Mix with a stirring rod and then test the resulting solution with litmus paper to make sure that it is basic. 9.Boil while stirring for about 5 minutes in order to concentrate the dye. Pour the resulting solution in a evaporating dish and heat it directly to evaporate to "just about dryness." It should be a little wet. Stir constantly while heating. If it does go dry, simply add a few drops of distilled water and stir. 10.Obtain the other 10x20 cm sheet of chromatography paper that was prepared in Step 1. Using the same procedure that was used in Part 1, spot the paper with the food dyes that were obtained CHROMATOGRAPHY from the M&M's. The paper should be spotted with each dye twice, or until each spot is dark. 11.Repeat Step 3 by placing the stapled chromatography paper in a 600 ml beaker containing 5 ml of vinegar. Cover the beaker with plastic wrap and allow to develop until the solvent line progresses nearly to the top of the paper (1 cm). 12.Remove the paper from the beaker, open it out and lay it on the piece of paper to dry. Make sure the solvent line is marked with a pencil all the way across the paper. 13.Use the ultra-violet lamp to observe the separations. 14.Refer to data charts to record your results from part A part B. CHROMATOGRAPHY DATA TABLE (PART A) _____________________________________________________________________________ DYES DISTANCE DYE(S) MOVED DISTANCE SOLVENT MOVED (CM) (CM) _____________________________________________________________________________ #5 Yellow _____________________________________________________________________________ Yellow #6 _____________________________________________________________________________ Red #40 _____________________________________________________________________________ Red #3 _____________________________________________________________________________ Blue #1 ____________________________________________________________________________ Blue #2 _____________________________________________________________________________ TABLE (PART B) _______________________________________________________________________________ M&M COLORS DISTANCE DYE(S) MOVED DISTANCE SOLVENT MOVED USED (CM) (CM) _____________________________________________________________________________ 1. _____________________________________________________________________________ 2. CHROMATOGRAPHY ______________________________________________________________________________ DATA ANALYSIS 1. Which FD&C food color has the longest retention time? Which has the shortest? 2. Calculate the Rf (retention factor) ratios for each of the six FD&C dyes used in part A. a) Yellow #5 Rf = __________________________________ b) Yellow #6 Rf = __________________________________ c) Red #3 Rf = ___________________________________ d) Red #40 Rf = ____________________________________ e) Blue #1 Rf = ____________________________________ f) Blue #2 Rf = ____________________________________ 3. Calculate the Rf ratio(s) per dye for the M&M colors you used. a) M&M 1 Rf = ______________________________________ b) M&M 2 Rf = ______________________________________ CHROMATOGRAPHY PURDUE UNIVERSITY INSTRUMENT VAN PROJECT (if necessary) Rf = ________________________________________ 4.Using the FD&C chromatogram and the calculated Rf values as standards, list the FD&C dyes used in your M&M experimental groups. M&M 1 has: _____________________________________________________ M&M 2 has: ______________________________________________________ 5.Why was blue #2 only seen with the ultraviolet lamp? 6.Why must packages of food using yellow dye #5 be required to list this ingredient? 7.Why were there no red M&M for several years? CHROMATOGRAPHY LAB WRITTEN BY: SCOTT KEGLEY AND RICHARD PARTEZANA CHROMATOGRAPHY TEACHERS' GUIDE SEPARATION OF F. D. & C. FOOD COLORS IN M&M CANDIES CLASSROOM USAGE This investigation is intended for a Chemistry 1 or Physical Science curriculum. PREPARATION Preparation time for set up should be less than 15 minutes. TIME It should be divided into two 45 - 50 minute periods. A pre-lab on chromatography and Part A can be done the first day and Part B the second. SAMPLE RESULTS M&M colors orange, yellow, and red are formed from only 1 dye. Colors green, light brown, and dark brown are combinations. a) M&M's FD&C Dyes Red Red #40 b)Yellow Yellow #5 c) Orange Yellow #6 d) Green Blue #1 and Yellow #5 e) Light Brown Red #40, Yellow #6, and Yellow #5 f) Dark Brown Red #40, Yellow #6, Yellow #5, and Blue #1 It is suggested to give each group of two students 1 color that is easy (red, yellow, or orange) and a second that is more difficult (green, light or dark brown). CHROMATOGRAPHY NOTES Be sure to cut the bottom corners of the chromatography paper below the 1 cm baseline or the runs will not be vertical. For determining the distance a dye moves, many methods can be used; measure to the top of the dye, measure to the darkest shade of the blot, measure to the bottom of the dye blot, etc. The only important aspect is to be consistent with whatever method used. REFERENCES Central Pennsylvania Association of Chemistry Teachers in Cooperation with NSF, Juniata College, and Private Industry. (1990). Student Laboratory Instrumentation Manual for Excellence. ASSESSMENT 1. Set up a student checklist: Student Name______________________ M&M Chromatography -exhibits on task behavior 1 2 -is contributing w/ lab partner 1 2 3 -makes careful measurements 1 2 3 -concentrated M&M dye well 1 2 3 -made careful spots on chromatography paper baseline 1 2 -stopped solvent line 1-2 cm from the top of the paper 1 2 3 -shows evidence of understanding procedure 1 2 3 -cleaned up work area 1 2 3 3 3 (circle one) CHROMATOGRAPHY -made proper recording of data during the procedure 1 2 3 -made appropriate observations during procedure 1 2 3 -wore goggles at all times 1 2 3 2. 10 minute activities A. Finished chromatograms are observed for dye components. B. Prepare chromatograph paper for a chromatography separation. (cut 10 x 20, cut corners, draw baseline, staple, etc.) C. Using notes, students will be given a combination of dyes and they must tell what M&M color they would form. D. Explain the following reversible equation: WOOL + DYE + H+ _ DYED WOOL+ 3. Activities for Portfolio A. Vee diagram B. Rf calculations and proper identification of M&M dyes C. Success in 10 minute activities