Amperometric titration

Amperometric titration.

1. 1 A SEMINAR ON AMPEROMETRY PRESENTED BY- AKASH u. THAKUR B.PHARM.VII st SEM (2016-2017) Guide By- Ass Prof. Mr. P V . Burakle

2. 2 Contents: 1. Amperometry - Introduction Principle Conditions for performing amperometric titration Apparatus for amperometric titration - Rotating Platinum Micro Electrode 2. Amperometric titration - Types of Amperometric titration. 3. Advantages of Amperometric titration. 4. Application of Amperometric titration.

3. Electrochemical titration - Analysis of chemicals or drugs can be done by using their electrochemical properties. Amperometric titrations - Introduction - Amperometric titrations are otherwise called as polarographic or polarometric titration because of the same similarity in principle. Principle - “ The principle is that, the potential applied between polarisable and non-polarisable electrode is constant and the diffusion current is measured during the titration .” During the titrations the conc. of the reducible ion change and Hence current also changes. 3

4. The current voltage curve of different conc. of same ion shows that, at low conc. Then there is less current and high concetration. There is more current during titration, then concentration of ions change. & current also change. 4

5. Conditions for performing amperometric titration- 1.Both should be reducible. 2.The potential applied should limiting current. Apparatus for amperometric titration - Rotating platium micro electrode (RPME) - It consist of a glass rod with platium wire at about 600 rpm wire are made through mercury. So that potential can applied & current is measured. 5

6. 2 . Types of amperometric titrations – 1) Titration of reducible ions vs non reducible ions. eg . Lead (pb) vs sulphate ions (So4) 2) Titration of non reducible ions vs reducible ions. eg . Chloride (cl) vs silver (ag) 3) Titration of reducible ion vs reducible ions. eg. Lead (pb) vs Dichromate ion 4) Redox titration (oxidant and reductant). eg. Ferric (fe3) ions vs titanous ions (ti) 5) End point techniques (karl fischer). (Determination of water using karl fischer reagent) 6

7. Titration of reducible ions vs non reducible ions. In which lead ions is titrated vs sulphate ions. Current is observed due to lead only. Decrease current due to decrease conc. of lead ions in solution due to ppt as lead sulphate by sulphate ions. 7

8. 8 2) Titration of non reducible ions vs reducible ions. In this titration of chloride ions with silver ions chloride ions are electroreducible, then current is minimun. when add of silver ions, dose not increase current and silver chloride ppt is formed at end point, add of silver ions & increase current.

9. 3) Titration of reducible ion vs reducible ions. Titration of lead ions with dichromate ions. decrease in current due to decrease in the conc. of lead ions and grdually ppt as lead chromate. After end point, addition of dichromate ions in solution then, increase current and V- shaped curve is obtained. 9

10. 10 4) Redox titration (oxidant and reductant). Oxidant and reductant gives diff. current. An eg.- titration of ferric ions against titranous ions. 1st part curve decrease current due to decrease conc. of ferric ions. When ferric ions are reducesed, the diffusion current minimum. 2 nd part of curve current set up by oxidation of titranous ions added. The end point shown by two lines intersection by difference in slope.

11. 11 5) End point techniques (karl fischer). The method is applicable when redox system is present before & after the end points. an eg. Water using karl fischer reagent. Small potential is applied between two similar platinum electrodes. When water is present both electrodes are depolarised and then Addiction of karl fischer A and B (solution of iodine and sulphur dioxide in methanol ) then till the end point. Where current is decrease at end point and only one electrode is depolarised and current is zero.

12. 12 3. Advantages of Amperometric titration. Both reducible as well as non- reducible ions groups can be determine. Dilute solution can be analysed. The reaction carryout can be reducible or irreversible. The appratus is simple and temprerature need not be provided constants. 4. Application of Amperometric titration. 1. Amperometric titration - quantitative in nature. used and determine the end point. 2.Determination of water by using karl fischer reagent. 3.Amperometric dectector - (HPLC)Amperometric dectector can detect very low conc. of reducible ions & they can easily determine. 4. Quantification of ion or mixture of ions.

13. REFERENCE - Text book of Pharmaceutical Analysis, fourth edition by Dr. S. Ravi Sankar. 13

14. THANK YOU 14