RP11

• How can Benedict's solution be used to measure the concentration of glucose in a solution?

  Use a colorimeter to measure the absorbance of a series of solutions of known concentrations to create a calibration curve. Compare the absorbance of an unknown sample to the calibration curve.
• What is a serial dilution?

  A dilution where successive concentrations increase/decrease in a logarithmic fashion
• Outline the procedure of this practical.

  Make a serial dilution of glucose from 0 to 10 mol dm-3

  add 2 cm3 of each of the unknown samples in separate boiling tubes. Followed by 2 cm3 of Benedict's solution.

  Place in a water bath at 90°C for four minutes.

  Zero the colorimeter using a cuvette with distilled water and set to red filter.

  Place known samples into cuvette and measure the absorbance of each using the colorimeter.Measure the absorbance of the unknown samples using the colorimeter. Use the calibration curve to determine glucose concentrations.

  Make a calibration curve.
• What are the axes in a calibration curve?

  Absorbance against glucose concentration.
• What would a high glucose concentration in urine suggest?

  It may suggest diabetes. Lack of insulin leads to high blood glucose concentration, hence high concentration in the glomerular filtrate, so not all glucose can be reabsorbed in the proximal convoluted tubule.
• State the hazards and precautions of this practical.

  Benedict's solution is an irritant, wear eye protection, avoid contact with skin.

  Handle the hot water bath with care.
• How can you increase the accuracy of the estimate of the unknown glucose solution?

  Increase the number of concentrations (at smaller intervals) for the calibration curve within the range of concentrations that the unknown solution belongs in.