required practical 11 Flashcards
production of a dilution series of a glucose solution and use of colorimetric techniques to produce a calibration curve with which to identify the concentration of glucose in an unknown ‘urine’ sample
how can benedict’s solution be used to measure the concentration of glucose in a solution?
use a colorimter 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 logorithmic fashion
method
- create a dilution series of glucose using distilled water, use six boiling tubes to make concentrations ranging from 0-10mmol dm-3
- place 2cm3 of each of the unknown samples in separate boiling tubes
- add 2cm3 of bendict’s solution to all tubes
- place boiling tubes in a water bath at 90c for 4 minutes
- use tongs to take out boiling tubes and let cool
- zero the colorimeter and set to red filter
- place samples and measure absorbance
- make calibration curve by plooting absorbance against known glucose concentrations
what would a high concentration of glucose in urine suggest?
may suggest diabetes as lack of insulin leads to high blood glucose concentration, hence high concentration in gomerulus filtrate, so not all glucose can be reabsorbed in PCT
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
