Pharmaceutical analysis- Complexometric titration
✯Complexometric titration✯
Methodology -;
• Titration of 0.1 NaCl by using 0.1N AgNOვ in the presence of indicator . ( 5 % solution) in conical flask.
• At the end point reddish brown ppt. Is obtained.
• Reading is taken from burette & calculate the concerntration of unknown sample.
Application of precipitation titration-;
• It is used for halide ion solution.
• It is used to measure salt content in food beverage & water.
Complexometric titration-;
• Those volumetric titration or analysis in which the end point is indicated by a coloured complex are known as complexometric titration.
• It is known as chelatometry.
In this type of titration on indicator is used which is capable of producing clear colour in titration which indicates end point of the titration.
Complexometric titration are used for determination of concerntration of metal ions in solution.
Calcien and Eriochrome black T indicator are used in complexometric titration.
Complexometric indicator/ metal ions indicator-;
• Complexometric indicator are those indicator which are used in complexometric titration. Those indicator undergoes a difinate colour change in presence of specific metal ions.
These indicator are also known as pH indicator or metallochromic indicator.
These are organic molecules soluble in water.
Example-; Calcien ,( for Ca, Mg , Cd) & Eriochrome black T ,( for Ca , Mg , Ba , Zn , Cd ,pb , and Hg ) murexide ( for Ca , Cu , Co).
Types of complexometric titration-;
1. Direct titration-;
• It is the most convenient and simple method of complexometric titration using EDTA . It is similar to acid - base titration.
• In this technique standard EDTA solution is added to given sample containing metal ion usign burette till the end point is achieved.
Copper, Barium , zinc , Mercury, aluminium, lead ,bismith, chromium etc are determined by direct method.
2. Back titration -;
• In this type of Titrations we perform back titration for excess amount of EDTA . Exces amount of EDTA is back titrated by solution of second metal ion .
3. Replacement titration-;
• This method is used when direct and back titration method don't give sharp end point.
• The metal to be analysed is added to metal - EDTA complex metal present in analyte displaces the another metal from - metal EDTA complex .
4. Indirect method -;
• Some anion form ppt. With metal cation . These anion do not react with EDTA . So these can be analysed by indirect titration with EDTA.
Ligands-!
• Are e- pair donar and form co- ordinate covalent bond with metal ion.
Ligands-types -;
1. Monodentate ( ammonia)
2. Multidentate ( bi , tri , tetra , penta , hexa etc).
Chelates -;
• When metal ion co- ordinate with two or more donar group of a single ligand & form five or six membered heterocyclic ring called chelates.
Masking agent-;
• Masking agent is a reagent that hide/ protect some component of the analyte from reaction with EDTA .
It is used to prevent one element from interfering in the analysis of another elements.
Example-; A mixture of Zn & Mg can be determined by treating the mixture with KCN which would form a complex with zn ion and the Mg ion can be titrated with EDTA .
Demasking agent -;
• Demasking agent is a reagent that release of a metal ion from a masking agents.
Example-; The masked zn ions can be liberated / demasked by treating with aldehyde such as farmeldehyde & titrated with EDTA.
Different techniques of analysis-;
1. Titration method
2. Spectroscopic techniques
3. Chromatographic method
1. Titration method
★Aqueous acid base titration-;
• A solution in which water has been used as a solvent.
Example-; Solution of common salt or sugar in water . An aqueous acid - base titration Is the determination of the concentration of an acid or base by exactly neutralizing the acid or base with an acid or base of known concentration.
This allows for quantitative analysis of the concentration of an unknown acid or base solution. Aqueous acid base titration can also be used to find percent purity of chemical.
★ Non - aqueous acid base titration-;
• Non aqueous titration is the titration of substance dissolved in solvent other than water • It provides a solvent in which organic compounds are soluble.
• The most commonly used procedure in this titration of organic bases with perchloric acid in anhydrous acetic acid.
• It is the most common titrimetric procedure used in pharmacopoeial assays and is suitable for the titration of very weak acids and very weak bases.
★ Redox titration-;
• A Redox titration is a titration in which the analyte and titrant react through an oxidation- reduction reaction.
• As in acid - base titration, the end point of a Redox titration is often detected using an indicator.
• A Redox titration is a type of titration based on a Redox reaction between the analyte and titrant.
• Concentration of certain chemical in pharmaceutical compound can be determined through Redox titration.
★Complexometric titration-;
• Complexometric titration is a form of volumetric analysis in the which the formation of a coloured complex is used to indicate the end point of a titration.
• particularly useful for the determination of a mixture of different metal ion in solution.
★Volumetric analysis-;
• Volumetric analysis is a quantitative analytical methods which is used widely.
• As the name suggests, this method involves measurements of the volume of a solution whose concerntration in known and appiled to determine the concentration of the analyte.
2. Spectroscopic techniques-;
★UV - Visible spectroscopy-
• The principle of UV visible spectroscopy is based in the absorption of ultraviolet light or visible light by chemical compound, which results in the production of distinct spectra . Spectroscopy is based on the interaction between light and matter.
★ Nuclear magnetic resonance spectroscopy-;
• Most commonly known as NMR spectroscopy or magnetic resonance spectroscopy-( MRS) is a spectroscopic techniques to observe local magnetic field and the NMR signal is produced by excitation of the nuclei sample with radio waves into nuclear magnetic resonance which is detected with sensitive radio receivers.
IR spectroscopy-;
★ The IR spectroscopy-theory utilizes the concept that molecules tends to absorb specific frequencies of light that are characteristic of the corresponding structure of the molecules.
The energies are reliant on the shape of the molecular surfaces, the associated vibronic coupling and the mass corresponding to the atoms.
3. Chromatographic method-;
★ Chromatography is usually a technique for separating and / or indentifying the components in a mixture.it is powerful method in Industry.
Thin layer Chromatography ( TLC).-;
• Chromatography works on the principle that different compound will have different solubilities and adsorption to the two phases between which they are to be partitioned .
Thin layer Chromatography is solid - liquid techniques in which the two phases are a solid and a liquid ( moving phases).
Paper chromatography-:
• Chromatography techniques that uses paper sheets or strip as the adsorbent being the stationary phases through which a solution is made to pass in called paper chromatography.
•It is an inexpensive method of separating dissolved chemical substances by their different migration rates across the sheet of paper.
It is a powerful analytical tools that uses very small quantities of material.
Paper chromatography was discovered by synge and Martin in the year 1943.
High performance liquid chromatography-;
• High performance liquid chromatography (HPLC) is a very efficient separation techniques, that is it yield excellent separation in a very short period of time .
HPLC is a form of column chromatography. It's frequently used in biochemistry and analytical chemistry to separate components mixture.
Importance of pharmaceutical analysis-;
1. Identify of the drugs in the formulated products.
2. Determination of active ingredient or additional impurities
3. Stability of the drugs
4. Rate of drug from its formulation.
5. Identify and the purity of pure that meet specifications.
6. Concentration of specified impurities.
7. Concentration of drugs in plasma or biological fluids.
8. Determine pka value , partition coefficient, solubilities, and stability of drug under development.
( The partition coefficient is defined as the ratio of the concerntration of a solute in the organic phase to its concentration in the water phases
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