PAG- Finding the concentration of glucose in urine using a colorimeter Flashcards
Background -
- 3 Million people in the UK live with diabetes
- A sign of diabetes is finding glucose in patients urine
- We are given a sample of urine and asked to find its concentration of glucose
Safety -
- wear eye protection, e.g goggles
- use a test tube holder when removing hot test tubes from water baths
Serial dilation
- Label 7 test tubes (0.32,0.16,0.08,0.04,0.02,.0.1)
- Use 10cm3 measuring cylinder to measure 10cm3 of 0.32M stock solution
- Add 0.32M glucose solution to appropriate test tube
3 stages in this experiment
- serial dilation
- benedicts test
- using a colorimeter
After we have added 0.32 M glucose solution to the 0.32 labelled test tube, what happens
- Use a measuring cylinder to add 5cm3 of distilled water to other test tubes
- Use a 5 cm3 MC to take out 5cm3 of solution in 0.32M test tube and add to test tube labelled 0.16M
- Invert test tube 3 times
how do we invert a test tube
- Put a test tube bung into a test tube
- turn test tube upside down
after we invert a test tube what do we do
- Use a new 5cm3 MC to take out 5cm3 of solution in 0.16 M test tube and add to 0.08M labelled test tube and invert again
- repeat for 0.04,0.02,0.01M test tubes
Carrying out reducing sugars test
- Take 2cm3 from solution in the 0.32 M test tube using a MC and add to new test tube
- Using a 1cm3 syringe, add 2cm3 of Benedicts quantitative solution
- repeat with all solutions and urine solution
- label new test tubes as _MB
After we have added Benedicts to our urine and glucose solution, what do we do
- Add to a water bath at 100 degrees for 5 minutes
- remove test tubes and place into test tube rack
- allow precipitate to settle to the bottom of the test tube
Measuring absorbance with colorimeter
- Label cuvette tray with glucose and urine concentrations
- Fill cuvette tray to the top with the solutions from _MB test tubes almost to the top, then place into slot in cuvette tray
- fill one cuvette tray with distilled water = blank/control
what should the colorimeter and filter be set to
colorimeter = 0.0
filter = 680 nm
when you place your first cuvette - should be the blank cuvette- into the colorimeter, what should the absorbance be
0.0
after doing the blank absorbance, how do we measure the absorbance of the other solutions
- place cuvette into colorimeter
- press reading button
- record absorbance
what happens in the Benedicts test because glucose is a reducing sugar
- Cu2+ reduces down to CU+
- forming precipitate
- the higher glucose concentration, the more precipitate
which side of the cuvette should light be passing through
- the clear side, not the opaque side so light can pass through
