Introduction Analysis of Food Dyes in Beverages AP* Chemistry Big Idea 1, Investigation 1 An Advanced Inquiry Lab Catalog o. AP7642 Publication o. 7642 Assume an investigative role and design a valid procedure using spectroscopy and graphical analysis to determine the concentration of FD&C food dyes in sports drinks. The investigation will develop and test your skills in preparing accurate serial dilutions, understanding spectroscopic measurements, and extrapolating from graphical data. Concepts Background qualitative the nature or type of compound in a sample, whereas a quantitative method provides numerical data for the amount of a compound in a sample. - - Increasing wavelength Increasing energy Stimulus Response gamma X-ray ultraviolet infrared radio, radar, TV Energy source System under study Analytical information Visible light violet indigo blue green yellow orange red Figure 1. Figure 2. - CHEM-FAX...makes science teaching easier. I7642 013014
or different from that of other chemical species in solution. How do scientists select the desired wavelength for spectrophotometry? - visible spectrum - A) versus wavelength (λ Administration for use in foods, drugs and cosmetics. These seven FD&C dyes give rise to the entire palette of artificial food colors. Three ture is characteristic of intensely colored organic dyes and pigments. is the color of light transmitted are absorbed complementary to the transmitted color. A color wheel (see Figure 4) provides a useful tool for identifying the colors or wavelengths of light optimum wavelength for spectrophotometric analysis of a dye solution is generally determined from the wavelength of maximum absorbance λ max a + a + P (T) is the fraction of incident light (P/P o and percent transmittance (% T A % T = T 100 = P/P o 100% Equation 1 FD&C Blue 1 Figure 3. red 640 700 nm violet 400 450 nm orange 600 640 nm blue 450 480 nm green 480 560 nm A T Equation 2 c Figure 4. yellow 560 600 nm P o P b Figure 5. c) as well as the path length of the sample cell (b) a - A = abc Equation 3 2 I7642
Experiment Overview optimum linear relationship among various functions (T, % T, log T and A Pre-Lab Questions (7.0 10 6 Absorbance 1 0.8 0.6 0.4 0.2 Absorption Spectrum for Blue 1 FD&C Dye 0 400 450 500 550 600 650 700 750 Wavelength, m Figure 6. Hint: 1 V 1 2 V 2. Dye Stock Solution (A) B C D E F G H 0 2 4 6 7 9 10 10 6 4 3 2 1 0 Background. The value of a 1 cm 1 and b = 1 cm. Materials Safety Precautions The FD&C dyes are slightly hazardous by eye and skin contact. The dyes have been stored with other, nonfood-grade chemicals and are not for consumption. Avoid contact with eyes, skin, and clothing. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines. 3 I7642
Introductory Activity 1. Turn on the spectrophotometer and allow to warm up for 15 20 minutes. ote: Hint: To avoid contaminating the Solution Stock (A) B C D E F G Blank (H) 0 2 4 6 7 9 10 10 6 4 3 2 1 0 length for this study. T T to transmittance (T T T. a) of cm at 630 nm and the path length (b 6 10. Prepare separate graphs of (a) % T, T, (c) 1/T, (d) log T, and (e) log T (on the y-axis) versus dye concentration (on the x-axis) for each solution. ote: Dye concentrations were calculated in the Pre-Lab Questions using the estimated concen- Guided-Inquiry Design and Procedure Concentration of FD&C Blue 1 in Beverages Introductory Activity, identify the optimum linear relationship or calibration curve for - - 5. - 4 I7642
Opportunities for Inquiry Absorbance Spectra and Analysis of Dyes λmax OCH 3 HO SO 3 a ao 3 S HO CH 3 ao 3 S SO 3 a ao 2 C FD&C Red 40 FD&C Yellow 5 Figure 7. 5 I7642
AP Chemistry Review Questions Integrating Content, Inquiry and Reasoning 1. Calculate the value of % T A 2+ - [Cu(H 3 ) 4 ] 2+ ion is often used as a positive test to verify the presence of Cu 2+ ions. a. tetraamminecopper(ii) sulfate. b. [Cu(H 3 ) 4 ] 2+ - λ max ) for Cu(H 3 ) 4 2+ λ max for Cu(H 2 O) 6 2+? Explain. - 6 I7642 2014 Flinn Scientific, Inc. All Rights Reserved. Reproduction permission is granted only to science teachers who have purchased Analysis of Food Dyes in Beverages, Catalog o. AP7642, from Flinn Scientific, Inc. o part of this material