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Testing carbohydrates. Quantitative Benedict’s Test

Testing carbohydrates. Quantitative Benedict’s Test. Objectives. Know how to produce and use a calibration curve Understand the meaning of the words qualitative and quantitative Be able to carry out a serial dilution. Key words.

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Testing carbohydrates. Quantitative Benedict’s Test

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  1. Testing carbohydrates. Quantitative Benedict’s Test

  2. Objectives • Know how to produce and use a calibration curve • Understand the meaning of the words qualitative and quantitative • Be able to carry out a serial dilution

  3. Key words Write what you think (or know) the words mean on a post it and stick it next to the correct word. calibration curve qualitative quantitative serial dilution colorimeter

  4. In many biochemical tests results can be either qualitative and quantitative qualitative= description e.g. it was brick red quantitative= has a numerical value. With the benedicts test this is achieved by measuring the absorbance of the solution using a colorimeter.

  5. Quantitative Benedict’s test Step 1. Make a series of solutions that have a known concentration of reducing sugar. This is achieved using the serial dilution method.

  6. Serial dilutions. Start with 2M glucose. Dilute with water to make a 1 in 10 dilution. =0.2M What would the next concentration be? 0.02M 0.002M 0.0002M

  7. Quantitative Benedict’s test Step 1. Make a series of solutions that have a known concentration of reducing sugar. This is achieved using the serial dilution method. Step 2. Carry out the Benedict’s test on each concentration. Step 3. Filter the liquid from the precipitate. Step 4. Measure the absorbance of the liquid using a colorimeter. Step 5. Make a calibration curve by plotting concentration against absorbance.

  8. Check learning… • Describe how you make a serial dilution. • What is a colorimeter and what is it used for? • What is the difference between qualitative and quantitative. • Describe how you would plot a calibration curve.

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