Research Question/Statement: Compare the amount of sugar in three different soft drinks. (DCP)
Introduction:
Benedicts Quantitative reagent can be used to measure the % glucose present in different solutions. You are given 3 different types of
clear, colourless soft drink to test. Measure their sugar content and compare your reading to find out if they are significantly different or
not.
Step 1: Building a calibration curve
Apparatus
 250ml Benedict’s quantitative solution (BQS)
 100ml 1% Glucose solution
 Distilled water
 2 x burettes and stands
 12 x 100ml beaker
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2 x 5ml syringe
11 test tubes and sufficient racks to hold them
11 cuvettes
Access to a colorimeter
Access to a waterbath set to 100oC
Method
1. Place a 1% solution of glucose in a burette.
2. Place water in another burette and prepare a series of glucose solutions (0%, 1%, 2% … 10%)
3. Label a series of test tubes to match the glucose concentrations.
4. Using a 5ml syringe add 5 ml of the appropriate concentration to each of the labelled test tubes. Rinse in distilled water between
uses.
5. Using a 5ml syringe Add 5 ml of BQS to each tube and place in a boiling water bath for a few minutes.
6. Allow the solutions to cool and any precipitates to settle (alternatively after cooling centrifuge the sample and use a pipette to
extract the supernatant) then add each of the solutions to a different cuvette.
7. Setup the colorimeter to use a red or orange filter (590-750nm). Use your blank, 0%glucose (distilled water), to zero the
colorimeter.
8. Record the absorbance of all the different glucose concentrations including the blank.
9. Use the readings to construct concentration calibration curve of % glucose and absorbance.
Step 2: Measuring the sugar content of the soft drinks
Apparatus
 3 different sweet colourless soft drinks (multiple
bottles/cans of each)
 500ml Benedict’s quantitative solution (BQS)
 2 x 5ml syringe
 30 test tubes and sufficient racks to hold them
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30 cuvettes
Access to a colorimeter
Access to a waterbath set to 100oC
Method
1. In to a test tube, add 5 ml (using the 5ml syringe) of the soft drink to 5 ml (using the other 5ml syringe) of BQS.
2. Label the test tube appropriately and place in a boiling water bath for a few minutes.
3. Read the absorbance using the colorimeter as setup in the calibration process
4. Repeat for each type of drink a minimum of 10 times to gain sufficient data
-- Manage the order of tasks to maximise your effective use of laboratory time --
Produced by Chris Paine 2011
Lab Report
Write up DCP only for this lab and answer the following points:
 You were given a number of different cans/bottles of drinks. Did the sugar content of the each drink vary from bottle to bottle?
What is your assessment of the quality control of the manufacturers?
 Suggest further steps: consider the problems, and if you can, potential solutions of using this method to measure the amount of
sugar present in sweetened tea drinks and solid foods such a varieties of apple
Produced by Chris Paine 2011