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Experiments Overview

Paper chromatography - Determination of selected cations

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Equipment:

Semi-micro centrifuge, semi-micro test tubes, vortex mixer (optional), hot-air gun (optional), atomiser sprayer, drying oven.

Apparatus:

Chromatography tanks, UV Viewing cabinet, #1 chromatography paper, capillaries, microcaps 5ul, spray chamber.

Chemicals:

Conc. ammonia soln., Thioacetamide 30% aq. soln.,rubeanic acid, 8-hydroxyquinoline, conc. HCl, acetone, and stock solns.

Solutions preparations:

1. 5% stock solns. of cations relative to the chlorides of their salts.

5% Al+3 = 45g of AlCl3.6H2O dissolved in 100ml dist. H2O
5% Cr+3 = 25g of CrCl2.6H2O dissolved in 100ml dist. H2O
5% Fe+3 = 24g of FeCl3.6H2O dissolved in 100ml dist. H2O
5% Co+2 = 20g of CoCl2.6H2O dissolved in 100ml dist. H2O
5% Ni+3 = 20g of Ni Cl2.6H2O dissolved in 100ml dist. H2O
5% Mn+2 = 17.5g of MnCl2.4H2O dissolved in 100ml dist. H2O
5% Zn+2 = 10g of ZnCl2 dissolved in 100ml dist. H2O

2. Reference solutions = 1% = standards = Al, Cr, Fe, Co, Ni, Mn, Zn.

Dilute the 5% solutions 1 in 5, and put in small vials for spotting.

3. Sample mixture: make up from 5% stock.

A = Al, Fe, Ni, Mn
B = Fe, Cr, Zn, Mn.
C = Al, Fe, Zn, Mn.

4. Visualizing agent

(a) Oxime (8-hydroxyquinoline). Dissolve 0.25g in 40mls ethanol and 100mls H2O.
(b) Rubeanic acid (dithioxide). Dissolve 0.1g in 100ml ethanol.

5. Developing solvent:

172mls of Acetone; 12mls of HCL; and 16 mls of H2O

Analytical notes:

1. Can use solids to make up the cation mixture.
2. Cut PC paper 19cm x 19cm pieces to fit inside the tank.
3. Keep Ammonia, Thiocetamide, and spray box in the Fume hood.
4. Keep a small beaker of boiling water on a hotplate or bath to dissolve group 2 ppt.
5. Use atomiser spray head to spray and visualize chromatogram (compressed air or air pump)

Operation of Instrument:

Follow User guide or get help from Technician, Demonstrator or Lecturer.




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