Chemistry: Glucose and Sports Drinks

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Determination of Sugars in Sports Drinks: A Spectrophotometric Analysis

By: Crystle Culling Student Number: 2686923 Class: Tuesday 12pm (odd weeks)

Page | 1

1015MSC Lab Report

Crystle Culling 2686923

The concentration of sugars in two well-known sports drinks, Powerade and Gatorade, were determined by monitoring an enzyme-catalysed reaction sequence involving the appearance of NADPH. Sucrose and glucose concentrations were calculated from the concentration of NADPH formed by the reaction of glucose-6-phosphate and NADP+. Spectrophotometric absorbance readings were taken at 340nm, this is because NADPH absorbs strongly at this wavelength, whilst NADP+ does not (1015MSC, 2010). The concentration of glucose and sucrose in Powerade was found to be 0.43g/100mL and 7.36g/100mL, whereas the concentration of glucose and sucrose in Gatorade was found to be 0.94g/100mL and 7.09g/100mL respectively.

Sports drinks such as Gatorade and Powerade have exploded onto the market with a growing popularity and high demand with consumers believing it to be a smarter alternative to water, and a healthier alternative to soft drinks. Debate over any benefits of such drinks has been in the media just as long as they’ve been on the shelves. An investigation into the sugar concentrations would allow health professionals to accurately assess the health consequences and make recommendations to the public regarding consumption. The use of enzyme-catalysed reactions followed by absorbance spectrophotometry can be successfully used to monitor reactions which involve either the appearance or disappearance of cofactors. NADPH absorbs ultraviolet light at a wavelength of 340nm, whereas NADP+ does not. This NADPH cofactor is released when glucose-6-phosphate reacts with NADP+ in the presence of an enzyme such as glucose-6phosphate dehydrogenase. This relationship between the concentration of this important cofactor and the concentration of sucrose and glucose ultimately allows for the determination of the sugar content of these different sports drinks.

Materials and Methods
This experiment was performed in accordance with the detailed steps outlined in Experiment 5 in the 1015MSC Laboratory Manual (1015MSC, 2010). In summary: Standard solutions of sucrose and citrate buffer were prepared and analysed with the spectrophotometer at 340 nm. After incubation, a TEA buffer and an enzyme solution were added and a comparison was made between the spectrophotometry of the two sports drinks and the standard solutions to determine the concentration of total glucose plus sucrose. This step was repeated without the citrate buffer to determine the glucose concentration. Page | 2

1015MSC Lab Report

Crystle Culling 2686923

As I did not attend this lab, the sample data provided was used as a basis for my results, discussions and calculations. Table 1 displays the absorbance readings following the first reaction sequence. These readings are indicative of sugar levels (i.e. both glucose and sucrose levels) in the diluted samples. Figure 1 is a graphical display of this data, showing the different concentrations plotted against the absorbance difference. This process was repeated for the absorbance readings of glucose levels in the second process. Table 2 displays the resultant absorbance readings, and Figure 2 is a graphical display of this data. Table 3 shows the final values of sucrose and glucose concentrations (g/100mL) found in Powerade and Gatorade.

Table 1: Spectrophotometric absorbance readings from the sucrose and glucose assay

Concentration (mM)
0 2 4 6 Powerade Gatorade

Absorbance 1 (@340nm)
0 0 0.013 0 0 0

Absorbance 2 (@340nm)
0 0.333 0.578 0.917 0.36 0.393

Absorbance Difference (A2-A1)
0 0.333 0.565 0.917 0.36 0.393

Figure 1: Relationship between the concentration of sucrose and glucose and spectrophotometric absorbance

Concentration of Glucose plus Sucrose vs. Absorbance of...
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