Total Carbohydrates Using the Phenol-Sulfuric Acid Method Essay

Custom Student Mr. Teacher ENG 1001-04 21 July 2016

Total Carbohydrates Using the Phenol-Sulfuric Acid Method

The standard curve of the unknown glucose solution was constructed in order to solve for the concentration of glucose in corn syrup and Gatorade samples. These calculations can be shown in the results section of the lab. Under proper conditions, the phenol-sulfuric method is accurate to ± 2% (Nielson 2010). This seems to be true with the %CV shown in Tables 2 and 3 in the Absorbance columns. However, the accuracy of the results is completely dependent on the accuracy of the standard curve.

If the standard curve were to be inaccurate, then the findings of the concentration of corn syrup and glucose would also be inaccurate. When comparing the labels of the samples, corn syrup contains 31 g sugar/ 30 mL. Corn Syrup would then equal 1033 g sugar/ L. This value is similar to the average of 835. 5 g/L that was calculated in lab. This value is seen in Table 2. This difference in values could be the cause of human error, such as not mixing the container so the solution was homogenous or transferring solution errors. Gatorade contains 21 g sugar / 355 mL according to the label.

Gatorade would then be equal to 59. 16 g sugar/L. This value is similar to the average of 70. 15 g/L Gatorade. This value can be seen in Table 3. This difference in values could again be due to a mixing error in lab. The concentration of glucose in the corn syrup and Gatorade (g glucose equiv/ g sample) can be found in Tables 2 and 3. Question 1. Light Karo Corn syrup is a mildly sweet, concentrated solution of dextrose and other sugars derived from cornstarch. Corn syrup contains between 15% to 20% dextrose (glucose) and a mixture of various other types of sugar.

(Karo 2010) It is not appropriate to only use glucose in constructing the standard curve because it would be better to have a known mixture of glucose and fructose. If a sample is known to contain only one carbohydrate, then the results must usually be expressed as glucose. However, since corn syrup is made up of dextrose solution and various other sugars derived from cornstarch, then the standard curve would need to be constructed based on using both known concentrations of glucose and fructose (Nielson 2010). Using just glucose would yield inaccurate results. References

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  • Date: 21 July 2016

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