Spectrophotometric Analysis of Gatorade Question: What concentration of Blue 1 and Red 40 dyes is used to create purple Gatorade? Goal: Determine concentration of Blue 1 and Red 40 dyes in system of simultaneous equations. Read section 18-­‐1 (p. 421-­‐422) in your textbook. Experimental Procedure: 1. Make a 100 mL 1.0 x 10-­‐3 M solution of Blue 1 dye. The manufacturer concentration of Blue 1 food coloring is 20% w/v. 2. Predict λmax of Blue dye solution based on color of solution and measure absorption spectrum. Was your prediction correct? 3. If absorbance at λmax is greater than 0.9, then perform at 1:10 dilution using a 10 mL volumetric flask. 4. Determine actual λmax and calculate ε. This is λB’ and εB’. 5. Repeat steps 1-­‐4, but use Red 40 dye. Manufacturer concentration of Red 40 food coloring is 30% w/v. 6. Determine ε for Red 40 dye at λmax (i.e., λB’) of Blue 1 solution. This is εR’. 7. Determine ε for Blue 1 dye at λmax (i.e., λR’’) of Red 40 solution. This is εB’’. 8. Setup a data table of λmax and ε similar to data table in the Example problem on p. 422. 9. Measure absorption spectrum of Gatorade solution. Make sure λmax for each dye is between A = 0.4 – 0.9. If A is not in proper range, then dilute solution appropriately. 10. Determine absorbance at each λmax. 11. Calculate concentration of Blue 1 and Red 40 using equation 18-­‐6 on p. 422. 12. Overlay Blue 1 and Red 40 pure solution spectra with Gatorade spectrum. Print and paste in lab notebook. 13. Show at least one sample calculation of the various calculations performed for this experiment. 14. Write a conclusion statement. 15. If time permits, perform a reproducibility and limit of detection experiment. 16. Print control chart, external standard calibration curve, and calculation LOD.