Experiment 11 Spectophotometric Analysis Of Caffiene And Benzoic Acid In Soft Drinks
Experiment 11
Title: Spectrophotometric analysis of caffeine and benzoic acid in soft drink.
Name: Tan Herh Lim
Name of partner: Sia Ting Wai, Chong Zheng Yee
Date:
Lecturer: Dr. Neo Kian Eang
Practical class: P1
Objective: To obtain the absorbance of the caffeine and benzoic acid in soft drinks.
Introduction
Soft drinks that commonly found in our daily life contain caffeine and sodium benzoate. The caffeine act as a stimulant and the sodium benzoate acts as a preservative of soft drink by inhibits grow of bacteria. In this experiment, hydrochloric acid is added to all solution to protonate the sodium benzoate to produce benzoic acid. Since the caffeine has no appreciable basicity, so it is neutral at pH 2. In this experiment, a spectrophotometric analysis of caffeine and the benzoic acid in soft drink is conducted to determine concentration of the caffeine and the benzoic acid mountain dew. The UV/Vis spectrometer is used and the ultraviolet absorbance is chosen to conduct the spectrophotometric analysis in this experiment. The UV/Vis spectrophotometer work by passing the light by strong lamp through a monochromator, which split the light into its component colours using a gratings. Then, the desired wavelength of light beam is direct through the sample compartment which the cuvette is placed by using the mirror and slit. At other side of the compartment, there is a detector which can determine the amount of light beam pass through the solution in the cuvette, thus the absorbance of the solution in the cuvette can be determined. In addition, the absorbance of light is determined by three factors which is the nature of the solution, concentration of the solution, and the distance of light travel through the solution (path length) which stated in the Beer-Lambert Law. For each wavelength of light that passing through the sample, the absorbance of a solution or sample is determined by calculate from the negative logarithm of ratio of the
Title: Spectrophotometric analysis of caffeine and benzoic acid in soft drink.
Name: Tan Herh Lim
Name of partner: Sia Ting Wai, Chong Zheng Yee
Date:
Lecturer: Dr. Neo Kian Eang
Practical class: P1
Objective: To obtain the absorbance of the caffeine and benzoic acid in soft drinks.
Introduction
Soft drinks that commonly found in our daily life contain caffeine and sodium benzoate. The caffeine act as a stimulant and the sodium benzoate acts as a preservative of soft drink by inhibits grow of bacteria. In this experiment, hydrochloric acid is added to all solution to protonate the sodium benzoate to produce benzoic acid. Since the caffeine has no appreciable basicity, so it is neutral at pH 2. In this experiment, a spectrophotometric analysis of caffeine and the benzoic acid in soft drink is conducted to determine concentration of the caffeine and the benzoic acid mountain dew. The UV/Vis spectrometer is used and the ultraviolet absorbance is chosen to conduct the spectrophotometric analysis in this experiment. The UV/Vis spectrophotometer work by passing the light by strong lamp through a monochromator, which split the light into its component colours using a gratings. Then, the desired wavelength of light beam is direct through the sample compartment which the cuvette is placed by using the mirror and slit. At other side of the compartment, there is a detector which can determine the amount of light beam pass through the solution in the cuvette, thus the absorbance of the solution in the cuvette can be determined. In addition, the absorbance of light is determined by three factors which is the nature of the solution, concentration of the solution, and the distance of light travel through the solution (path length) which stated in the Beer-Lambert Law. For each wavelength of light that passing through the sample, the absorbance of a solution or sample is determined by calculate from the negative logarithm of ratio of the