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![Werner’s Co-ordination Number
Total number of ligands or atom which are directly
attached to the central metal atom is called as
Werner’s Co-ordination Number.
Eg:- Fe[H2O]6
Iron atom bond to 6 water molecule.
The co-ordination number of iron is 6.](https://image.slidesharecdn.com/complexometrictitration-250416154935-5b8d9e05/75/COMPLEXOMETRIC-TITRATION-PHARMACEUTICAL-ANALYSIS-8-2048.jpg)
![(1º COLOR)
(2º COLOR)
(1º COLOR)
Eg- M + In --------- [M-In]
(blue) (red)
[M-In] + EDTA ------ [M-EDTA] + In
(blue)](https://image.slidesharecdn.com/complexometrictitration-250416154935-5b8d9e05/75/COMPLEXOMETRIC-TITRATION-PHARMACEUTICAL-ANALYSIS-17-2048.jpg)
![Replacement of Metal ion titration
When metal ion (sample) forms a weak complex with indicator.
No satisfied end point.
STANDARD METAL ION is added to the sample
It forms a complex with indicator.
Blank titration is performed.
Difference btw 2 titer value------amount of titrant required to neutralize
the sample
Eg- Calcium gluconate----assayed by replacement of metal ion titration.
To the sample solution, MgSO4 is added and titrated against EDTA using
Mordant BlackII (Indicator)
[Mg-In] is stronger than [Ca-In] complex
Produce accurate end point](https://image.slidesharecdn.com/complexometrictitration-250416154935-5b8d9e05/75/COMPLEXOMETRIC-TITRATION-PHARMACEUTICAL-ANALYSIS-24-2048.jpg)
![[Mg-In] > [Ca-In]](https://image.slidesharecdn.com/complexometrictitration-250416154935-5b8d9e05/75/COMPLEXOMETRIC-TITRATION-PHARMACEUTICAL-ANALYSIS-25-2048.jpg)
![PRINCIPLE
Based on the substitution complexometric titration.
Replacement of Mg2+ ions from [Mg-In] complex occurs.
Indicator- mordant black II (doesn't give distinct color change
at the end point)
So known volume of MgSO4 is added to calcium gluconate.
Initially Ca & Mg ions are present in the solution, when
indicator is added it forms complex with Mg as [Mg-In] is
stronger than [Ca-In] complex------pink color
When titration proceeds, EDTA forms complex with Ca ions as
[Ca-EDTA] is stronger than [Mg-EDTA] complex
When all Ca ions get complexed, free Mg2+ forms complex
with EDTA.](https://image.slidesharecdn.com/complexometrictitration-250416154935-5b8d9e05/75/COMPLEXOMETRIC-TITRATION-PHARMACEUTICAL-ANALYSIS-41-2048.jpg)
![ End point is reached when [Mg-In] complex get breaks, liberates free Mg2+
ions & In- ions.
Free indicators ions produce blue color to the solution.](https://image.slidesharecdn.com/complexometrictitration-250416154935-5b8d9e05/75/COMPLEXOMETRIC-TITRATION-PHARMACEUTICAL-ANALYSIS-42-2048.jpg)
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COMPLEXOMETRIC TITRATION, PHARMACEUTICAL ANALYSIS
- 1. COMPLEXOMETRIC TITRATION ASWINI SASIDHARAN Assistant Professor NirmalaCollege Of Pharmacy
- 2. COMPLEXOMETRIC TITRATION Volumetricanalysis. Analyte (magnesium, calcium, lead, cobalt, bismuth) is titrating against complexing agents to form metallic complex.
- 3. COMPLEXING AGENT Substancesused to make a complex with metal ion. It contain electron donating group which form a covalent bond with metal ion and make a complex.
- 4. LIGAND A complexingagent is any electron donating ion or molecule usually called as ligand.
- 5. CHELATE Combining moleculescontaining two or more groups that can donate electron. This complex is known as chelate.
- 6. COMPLEX Metal ioncombines with a molecule of complexing agent which donate electron. The resulting compound is termed as complex.
- 7. SEQUESTERING AGENT Ligandis an electron donating ion or molecule which forms only single covalent bond with metal ion. It is known as sequestering agent.
- 8. Werner’s Co-ordination Number Total number of ligands or atom which are directly attached to the central metal atom is called as Werner’s Co-ordination Number. Eg:- Fe[H2O]6 Iron atom bond to 6 water molecule. The co-ordination number of iron is 6.
- 9.
- 10. PRINCIPLE Indicator usedfor titration is also a complexing agent. First indicator forms complex with metal ion which produces a colored complex. When it is titrated with a complexing agent it produces metallic complex. Indicator gets free.
- 11. CLASSIFICATION OF COMPLEXINGAGENTS Based on the number of electron donating groups Unidentate / Monodentate Bidentate Multidentate
- 12. Unidentate/Monodentate It donateonly one pair of electron NH3 Eg:- NH3 – It is used for the determination of copper and cobalt. - It contains only 1 electron donating groups.
- 13. Bidentate It has2 electron donating groups. Eg:- Ethylene diamine Determination of Mg, Zn, Ca, etc. It has 2 electron donating groups.
- 14. Multidentate It hasmultiple number of electron donating groups. Eg:- EDTA (Ethylene diamine tetra acetic acid). Determination of all metal ion. It has 6 electron donating group - Hexadentate
- 15. PM INDICATORS (Metalion indicators) These indicators are also complexing agents. (MAKE COMPLEX WITH ANALYTE) It also contain electron donating group. Once it forms a complex with metal ion, the color of the solution changes. Metal ion + Indicator ------- M-In Complex
- 16. PM INDICATORS Duringthe titration, complexing agent and metal ion form a complex at the end point. At the end point metal-indicator complex will break and the metal ion reacts with complexing agent. Hence the indicator will set free which gives 1º color to the solution. Eg- Mordant black II or Erlochrome black T (BLUE COLOR)
- 17. (1º COLOR) (2º COLOR) (1ºCOLOR) Eg- M + In --------- [M-In] (blue) (red) [M-In] + EDTA ------ [M-EDTA] + In (blue)
- 18. Eg- mordant blackII blue -------- complex -------- red
- 19. Eg- Calmagite blue --------complex -------- red
- 20. Eg- Murexide reddish violet-------- complex -------- blue
- 21. TYPES OF COMPLEXOMETRICTITRATION DIRECT TITRATION BACK TITRATION REPLACEMENT OF METAL ION TITRATION ALKALIMETRIC TITRATION
- 22. Direct Titration Simpletitration Complexing agent directly titrated with metal ion using suitable indicator. Eg- MgSO4 – titrating against EDTA – Mordant black II Similar to acid base titration. Metal ions- Cu, Ba, Zn, Hg, Pb, etc. MgSO4 + EDTA -------- Mg-EDTA complex + SO4 LIMITATION Not applicable for slow complexation.
- 23. Back Titration Tothe Sample solution (metal ion)-excess amount of complexing agent(titrant) is added. Resulting solution is back titrated using ZnO. Eg- Mn(OH)2 is assayed by back titration using ZnO (TITRANT), Mordant black II (Indicator) Difference between 2 titration – amount of EDTA reacted with Mn(OH)2
- 24. Replacement of Metalion titration When metal ion (sample) forms a weak complex with indicator. No satisfied end point. STANDARD METAL ION is added to the sample It forms a complex with indicator. Blank titration is performed. Difference btw 2 titer value------amount of titrant required to neutralize the sample Eg- Calcium gluconate----assayed by replacement of metal ion titration. To the sample solution, MgSO4 is added and titrated against EDTA using Mordant BlackII (Indicator) [Mg-In] is stronger than [Ca-In] complex Produce accurate end point
- 25.
- 26. Alkalimetric Titration Metalion + complexing agent----- corresponding acid Acid is back titrated by alkalimetric titration. Eg- NaOH using acid-base titration
- 27. Eg- Estimationof MgSO4 After the addition of EDTA, H2SO4 is produced. H2SO4 is produced is equal to the amount of MgSO4 H2SO4 back titrated against NaOH using Phenolphthalein.
- 28. Masking agents Itact either precipitation or complexation with the metal ion, that interferes in the complexometric titration. MASKING BY PRECIPITATION PRECIPITATING AGENTS METAL ION MASK Sodium sulphide Ca, Cu, Pb Sulphate Pb, Ba Oxalate Ca, Pb Fluorides Ca, Mg, Pb Ferrocyanide Zn, Cu 8-hydroxyquinoline Metal ions Thioglycerol Cu
- 29. MASKING BY COMPLEXFORMATION COMPLEXING AGENT USED FOR MASKING METAL ION MASK Aluminium Fluoride Al, Fe, Ti Ascorbic acid Fe Potassium cyanide Cu, Ag, Hg, Fe, Zn, Cd, Co, Ni Potassium iodide Hg Triethanol amine Al, Fe, Mn
- 30. DEMASKING AGENTS Processby which masked substances regains its ability to enter into a particular reaction. It helps to determine a series of metal ions in the solutions.
- 31. Eg- Cyanidecomplexes of zinc & cadmium is demasked with formaldehyde solution.
- 32. Eg- usingmasking and demasking reagents for the assay of mixture of 3 metals – Cu, Cd, Ca STEP 1 Direct titration of mixture with EDTA
- 33. STEP 2 Cu and Ca is masked by addition of cyanide, leaving only calcium ions
- 34. STEP 3 Formaldehyde is added to the cyanide containing mixture only Cd is demasked.
- 35. ESTIMATION OF MAGNESIUMSULPHATE Synonyms: Epsom Salts MgSO4. 7H2O Mol. Wt - 246.5 Colorless crystals or a white crystalline powder.
- 36. PRINCIPLE MgSO4 formscomplex with EDTA. Mordant black II mixture is added as indicator. Pink color in presence of Mg (Mg-In Complex). Blue in color in absence of Mg. So end point --------------- blue
- 37. Standardization of 0.05M Disodium EDTA Weigh accurately about 0.8g granulated Zn. Dissolve by gentle warming in 12ml of dil.HCl & 0.1ml bromine water. Boil to remove excess bromine, cool & add sufficient water to produce 200ml. Pipette out 10ml from it & neutralize with 2M NaOH. Dilute to 75ml with water. Add sufficient ammonia buffer (PH-10) to dissolve the ppt. Add 5ml in excess. Add 50mg of mordant black II & titrate with 0.05M EDTA until solution turns green.
- 38.
- 39. Assay of MgSO4 Weigh 0.3g of MgSO4, dissolve in 50ml water. Add 10ml strong ammonia-ammoniumchloride solution. Titrate with 0.05M EDTA using mordant black II. End point= Pink ---------Blue
- 40. ESTIMATION OF CALCIUM GLUCONATEBY COMPLEXOMETRY Mol. Wt. 448.4 Calcium Gluconate is calcium D-gluconate monohydrate. White, crystalline powder or granules.
- 41. PRINCIPLE Based onthe substitution complexometric titration. Replacement of Mg2+ ions from [Mg-In] complex occurs. Indicator- mordant black II (doesn't give distinct color change at the end point) So known volume of MgSO4 is added to calcium gluconate. Initially Ca & Mg ions are present in the solution, when indicator is added it forms complex with Mg as [Mg-In] is stronger than [Ca-In] complex------pink color When titration proceeds, EDTA forms complex with Ca ions as [Ca-EDTA] is stronger than [Mg-EDTA] complex When all Ca ions get complexed, free Mg2+ forms complex with EDTA.
- 42. End pointis reached when [Mg-In] complex get breaks, liberates free Mg2+ ions & In- ions. Free indicators ions produce blue color to the solution.
- 43. Assay of calciumgluconate Weigh 0.5g calcium gluconate. Dissolve in 50ml warm water. Cool & add 5ml of 0.05M MgSO4. Add 10 ml of strong ammonia solution. Titrate with 0.05M EDTA using mordant black II.