2800Kool-Aid

2800Kool-Aid - SPECTROPHOTOMETRIC ANALYSIS OF CAFFEINE AND...

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SPECTROPHOTOMETRIC ANALYSIS OF CAFFEINE AND BENZOIC ACID IN COLA BRITTNEY BROWN, KENNESAW STATE UNIVERSITY, KENNESAW, GEORGIA. PARTNER: ERICA FRANCIS CHEM 2800L November 10, 2010
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Brown 11/3/2010 INTRODUCTION: The purpose of this experiment was to quantitatively determine the amount two major species, Caffeine and Benzoic Acid in a soft drink using ultraviolent absorbance. Caffeine is an addictive used as a stimulant and benzoate is used as a food preservative in the beverage. In order to determine the concentration of caffeine and benzoic acid a series of dilution steps were performed. Calibration curves were created for pure samples of caffeine and benzoic acid. Based on Beer’s law, the absorbance of the solution that contains more than one chromophore will equal the sum of the absorbances of each component at a given wavelength (λ m ) using Equation (1): (1) By knowing the optical path length ans optical absorptivities of the individual components, the concentration of each chromophone can be determined by measuring the total absorbance at a given wacelength and solving for the matrix using Equation (2) and (3): (2) (3) So the concentration of each chromophore can be determined by measuring the total absorbance at a particular wavelength and solving the matrix equations (2) and (3) below when the optical absorptive of the individual components are known. Since only caffeine and benzoic acid are being analyzed n=2 so only two equations are needed. 2
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Brown 11/3/2010 made available commercially contains both citric acid and ascorbic acid. To determine the amount of each acid, a titration with standardized NaOH was performed. Both acids react with NaOH according to Reactions (1) and (2): C 6 H 8 O 7 + 3NaOH → Na 3 C 6 H 5 O 7 + 3H 2 O (1) C 6 H 8 O 6 + NaOH → NaC 6 H 7 O 6 + H 2 O (2) Considering both acids will react with the NaOH, the titration of the acids with NaOH only determines the amount of the total acid in the sample of Kool-Aid. The moles of total acid that reacted can be determined by Equation (1): = Liters NaOH x Molarity NaOH x Mole ratio x 25 moles total acid (1) A titration with KIO 3 will determine the amount of ascorbic acid taking into account that citric acid does not react with KIO 3 according to Reactions 3-6. IO
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This note was uploaded on 02/03/2011 for the course CHEM 2800 taught by Professor Staff during the Fall '08 term at Kennesaw.

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2800Kool-Aid - SPECTROPHOTOMETRIC ANALYSIS OF CAFFEINE AND...

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