RP11: Measuring Conc Of Glucose Using A Calibration Curve

Question 1

How can Benedict’s solution be used to measure the conc of glucose in a solution

Answer 1

Use a colorimeter to measure absorbance of a series of solutions of known concs to create a calibration curve.

Compare absorbance of an unknown sample to calibration curve

Question 2

What is serial dilution

Answer 2

Solution where successive concs increase/decrease in a logarithmic fashion

Question 3

Outline procedure of this practical

Answer 3

1. Make a serial dilution of glucose, ranging from 0 to 10 mmol dm-3
2. Place 2 cm3 of each of the unknown samples in separate boiling tubes.
3. Add 2 cm3 of Benedict’s solution to all boiling tubes.
4. Place boiling tubes in a water bath at 90°C for four minutes.
5. Zero the colorimeter using a cuvette with distilled water and set to red filter.
6. Place known samples into cuvette and measure the absorbance of each using the colorimeter.
7. Make a calibration curve.
8. Measure the absorbance of the unknown samples using the colorimeter. Use the calibration curve to determine glucose concentrations.

Question 4

What are axes in a calibration curve

Answer 4

Absorbance against glucose conc

Question 5

What would high glucose conc in urine suggest

Answer 5

May suggest diabetes

Lack of insulin leads to high blood glucose conc

Hence high conc in glomerular filtrate

So not all glucose can be reabsorbed in proximal convoluted tubule

Question 6

State hazards and precautions of this practical

Answer 6

Benedict’s solution is an irritant, Wear eye protection, avoid contact with skin

Handle hot water bath with care

Question 7

How can you increase accuracy of estimate of unknown glucose solution

Answer 7

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