Sunday, December 13, 2015

Cholera Vaccine

The holiday season is here, and some friends have decided to visit Panama (where else would an Engineer want to go for a holiday but to the Panama Canal?). One of the diseases they want protection against before traveling there is cholera which is caused by a water-born bacteria. The product they are taking is called DUKORAL® which comes in two parts. The first part part is a glass vial containing a whitish fluid which is the oral vaccine made up of inactivated cholera bacteria, which is probably of interest to the biology students reading this. Chemistry students, however, will be much more excited by the second part; a sachet containing a dry granular powder which is labelled as buffer.
The ingredients listed on the buffer sachet are:
  • sodium bicarbonate
  • citric acid, anhydrous
  • raspberry flavour
  • sodium carbonate, anhydrous
  • sodium citrate
  • saccharin sodium
The instructions for use by adults are:
  1. Dissolve the effervescent granules from the buffer sachet in a glass of cool water (approximately 150 mL)
  2.  Shake the vaccine vial
  3. Add the vaccine to the effervescent (bubbly) solution. Mix well and drink mixture.
And, you have to take two of these doses 1 to 6 weeks apart, and 2 weeks before arrival at your destination.
The good news is that most people should be protected cholera for up to two years, so I guess my friends will make their way back to the tropics next year.

Suggested Reading

Suggested Study Questions
  1.  What is another, systematic name for sodium bicarbonate?
  2. Give the molecular formula for each of the following:
    • sodium bicarbonate
    • citric acid, anhydrous
    • sodium carbonate, anhydrous
    • sodium citrate
  3. Draw a structural formula for each of the following:
    • sodium bicarbonate
    • citric acid, anhydrous
    • sodium carbonate, anhydrous
    • sodium citrate
  4. Use chemical terms to explain the relationship between:
    • sodium bicarbonate and sodium carbonate
    • citric acid and sodium citrate
  5. Explain what a buffer is.
  6. Explain why the dry, granular powder in the sachet was labelled "buffer".
  7. Why do you think a buffer is needed for this vaccine to be effective?
  8. What type of chemical compound is the "raspberry flavour" likely to be?
  9. One molecule responsible for raspberry flavour is shown below:
    What 2 reactants would you need to produce to this molecule in the school laboratory?
  10. What does the term effervescent mean?
  11. Write a balanced chemical equation to show why effervescence is observed when the buffer in the sachet is added to water. 
  12. What does the term "anhydrous" mean?
  13. Why are some of the buffer sachet's ingredients listed as "anhydrous"?
  14. What is the purpose of the saccharin in the buffer sachet?

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