Lecture 10

Question 1

• why is it important to anyalze minerals in food?

Answer 1

• nutrtional value
  
  • fortfication vs natrually present
  • effect of transformation
  • quality of water used

Question 2

• What minerals are currently on food labeling?
  -

Answer 2

potassium
- calcium
- iron
- sodium

Question 3

• categorize minerals into macro elements, trace and toxic

Answer 3

1. macro: daily need is greater or equal to 100 mg and includes **Ca, P, Na,K,Cl, S**
   
   2. trace: daily need a few ug and includes **Fe, Zn, Cu, I**
   3. Toxic: As, Pb, Hg, Cd, Al

Question 4

• What are the 4 categories of anayltic methods of mineral anaylsis?

Answer 4

1. atomic absorbtion
   
   2. titration
   3. colorimetry
   4. selective ion electrodes

Question 5

• Describe the principle of atomic absorbtion

Answer 5

• lamp has a target element so a specific wavelength and therefore only that will absorb
  
  • has heat to atomize sample, so there is seperate atoms
  • lens, prism and dector will collect wavelengths passing through and detect them
  • sensitive and can be used for trace elements

Question 6

• Describe the titration method complexometric

Answer 6

• a complex is formed by metal plus ligand
  
  • using a metal ion indicator, there will be a color change when bound to a metal ion
  • pink color is made as the inidcator binds to ion, when all ions are released from indicator and end point is reached a blue color will occur

Question 7

• What is the main use in color strips based on the complexometry method

Answer 7

detecting the quality of water

Question 8

• Describe the titration of sodium via the mohr method
  -

Answer 8

Cl is titrated with silver nitrate forming AgCl and the excess Ag will react with chromate also in solution forming orange red solid
- volume of sodium nitrate used used to quanitfy amount of NaCl

Question 9

• describe titration using volhard method

Answer 9

• in an acidic condition a back titration is done
  
  • excess silver nitrate is added to react with Cl forming AgCl
  • then the excess Ag is titrated with SCN forming AgSCN
  • a ferric ion indicator is used turning solution red
  • to calculate the volume of SCN related to the excess of Ag is used to calculate volume of Ag that reacted with Cl

Question 10

• Describe titration with strips based on Mohr techinque

Answer 10

• chlordie titration that is done by quantab strips, adaption of mohr technique that is fast and accurate

Question 11

• Describe Colorimetry method

Answer 11

• using visible spectrophemtry chromogen reacts with mineral that forms a colored compound that can be detected

Question 12

• describe the method using selective ion electrodes (potntiometry)
  -

Answer 12

these electrodes have selective membranes allowing only one type of ion to diffuse between solution and sample