Different techniques of analysis

Different Techniques of analysis like titration methods are explained

1. Different Techniques of analysis Mrs.Poonam Sunil Aher  ( M.Pharm , PhD) Assistant Professor Sanjivani College of Pharmaceutical Education and Research (Autonomous),  Kopargaon , Ahmednagar-423603 (M.S.), INDIA Mobile: [phone]

2. Types of Analytical methods 1. Quantitative methods 2. Qualitative Methods

3. Quantitative Analysis Technique 1. Solubility 2.Limit Tests 3.Melting Point 4. Boiling Point 5. Density 6. Specific Activity 7. Refractive index 8. Viscosity 9.Optical Rotation 10. Particle size 11. Purity determination 12. Assay or Recovery

4. Qualitative Analysis Techniques 1. Colour 2. Odour or smell 3. Appearance 4. Description 5. Identification tests 6. Colour tests

5. 1. Titrimetric Techniques of Analysis: Titration which is also known as titrimetry is a chemical qualitative analysis technique that is used to calculate the concentration of a given analyte in a mixture. Titration is an important technique in the field of analytical chemistry and is sometimes referred to as volumetric analysis also.

6. Types of Titration: Acid-Base Titration Redox Titration Iodimetry Titration Iodometry Titration Gravimetric Analysis Aqueous and Non Aqueous type of titration Precipitation Titration

7. Difference Between Titrant and Titrate The titrate is the analyte of interest whose identity is known, but its concentration is not. The titrant is the reagent whose identity and concentration are both known and is added incrementally to the titrate to determine its concentration. Titrate or Titrand : Unknown concentration and it is present in conical flask Titrant: Known concentration and it is present in Burette

8. Acid Base Titration An  acid–base  titration  is a method of  quantitative analysis  for determining the  concentration  of an  acid  or  base  by exactly  neutralizing  it with a  standard solution  of base or acid having known concentration. A  pH indicator  is used to monitor the progress of the  acid–base reaction . If the  acid dissociation constant  ( p K a ) of the acid or base dissociation constant ( p K b ) of base in the  analyte  solution is known, its solution concentration ( molarity ) can be determined. Alternately, the p K a  can be determined if the analyte solution has a known solution concentration by constructing a  titration curve .

9. Indicator choice A suitable pH indicator must be chosen in order to detect the end point of the titration. The colour change or other effect should occur close to the  equivalence point  of the reaction so that the experimenter can accurately determine when that point is reached. The pH of the equivalence point can be  estimated  using the following rules: A strong acid will react with a strong base to form a neutral (pH = 7) solution. A strong acid will react with a weak base to form an acidic (pH < 7) solution. A weak acid will react with a strong base to form a basic (pH > 7) solution. When a weak acid reacts with a weak base, the equivalence point solution will be basic if the base is stronger and acidic if the acid is stronger. If both are of equal strength, then the equivalence pH will be neutral. However, weak acids are not often titrated against weak bases because the colour change shown with the indicator is often quick, and therefore very difficult for the observer to see the change of colour . The point at which the indicator changes colour is called the  end point . A suitable indicator should be chosen, preferably one that will experience a change in colour (an end point) close to the equivalence point of the reaction

10. Acid Base Indicators

11. Example of Acid Base Titration 1. Standardization of NaOH with Oxalic Acid Oxalic acid-0.1 M solution Indicator- Phenolphthalein End Point- Colorless to pink 2. Standardization of 0.1 M HCl HCl: 0.1.M Indicator: Methyl Red End Point: Colorless to pink

12. 1. Neutral Acid Base Indicators Natural Indicator is a type of indicator that can be found naturally and can determine whether the substance is an acidic substance or a basic substance. Some examples of natural indicators are  red cabbage, turmeric, grape juice, curry powder, cherries, beetroots, onion, tomato , etc.

13. Redox titration Redox titration is based on an oxidation-reduction reaction between the titrant and the analyte. It is one of the most common laboratory methods to identify the concentration of unknown analytes. In order to evaluate redox titrations, the shape of the corresponding titration curve must be obtained. In these types of titration, it proves convenient to monitor the reaction potential instead of monitoring the concentration of a reacting species.

14. Reduction A substance can undergo reduction can occur via: The addition of hydrogen. The removal of oxygen. The acceptance of electrons. A reduction in the overall oxidation state. Oxidation The following points describe a substance that has undergone oxidation. The addition of oxygen. Removal of hydrogen which was attached to the species. The donation/loss of electrons. An increase in the oxidation state exhibited by the substance. Thus, it can be understood that redox titrations involve a transfer of electrons between the given analyte and the titrant. An example of redox titration is the treatment of an iodine solution with a  reducing agent . The endpoint of this titration is detected with the help of a starch indicator.

15. Iodometry Titration Redox titration using  sodium thiosulphate , Na 2 S 2 O 3  (usually) as a reducing agent is known as iodometric titration since it is used specifically to titrate iodine. The iodometric titration is a general method to determine the concentration of an oxidising agent in solution. In an iodometric titration, a starch solution is used as an indicator since it can absorb the I 2  that is released. This absorption will cause the solution to change its color from deep blue to light yellow when titrated with standardized thiosulfate solution. This indicates the end point of the titration. Iodometry is commonly used to analyze the concentration of  oxidizing agents  in water samples, such as  oxygen saturation  in ecological studies or  active chlorine  in swimming pool water analysis.

16. Iodimetry Titration And Eudiometry Iodimetry covers the titrations with a standard solution of iodine. In this method interconversion of elemental iodine to iodide ion I2=2e- --------------- 2 I- It direct Titration Method Here Iodine is directly reacted with reducing analyte with one redox reaction Iodimetry can not perform in strongly alkaline solution because it forms hypoiodide

17. Gravimetric Analysis Gravimetric analysis is a method in  analytical chemistry to determine the quantity of an analyte based on the mass of a solid. Example: Measuring the solids suspended in the water sample – Once a known volume of water is filtered, the collected solids are weighed. The principle of Gravimetric Analysis: The principle behind the gravimetric analysis is that the mass of an ion in a pure compound and can be determined. Later, used to find the mass percent of the same ion in a known quantity of an impure compound.

18. Steps followed in the Gravimetric Analysis Preparation of a solution containing a known weight of the sample. Separation of the desired constituent. Weighing the isolated constituent. Computation of the amount of the particular constituent in the sample from the observed weight of the isolated substance. Types of Gravimetric Analysis There are 4 fundamental types of gravimetric analysis. Of which, there are 2 common types involving changes in the phase of the analyte to separate it from the rest of a mixture, resulting in a change in mass. Volatilisation gravimetry Volatilisation Gravimetry involves separating components of our mixture by heating or chemically decomposing the sample. Precipitation gravimetry Precipitation Gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid. Electrogravimetry Electrogravimetry is a method used to separate and quantify ions of a substance, usually a metal. Thermogravimetry Thermogravimetry is a method of thermal analysis in which changes in physical and chemical properties of materials are measured as a function of increasing temperature or as a function of time.

19. Advantages of Gravimetric Analysis If the methods are followed carefully, it provides exceedingly precise analysis. It is used to determine the atomic masses of many elements to six-figure accuracy. It provides little room for instrumental error and does not require a series of standards for calculation of an unknown. Disadvantages of Gravimetric Analysis It usually provides only for the analysis of a single element, or a limited group of elements, at a time. Comparing modern dynamic flash combustion coupled with gas chromatography with traditional combustion analysis.

20. Aqueous titration This is also called neutralization type of titration. Here strong acid or base react with strong base or acid. Simultaneously weak acid or base react with weak base or acid. Neutralization Indicators are used. In case of weak acid and strong base titration Indicators used in alkaline range. Examples are: Thymol blue, Phelphthalein , Thymolphthalein In case of weak base and strong acid titration Indicators used in acidic range. Examples are: Methyl orange, Methyl red, Bromocresol Green

21. Non Aqueous Titration Here water is not used in titration therefore the name is non aqueous means no water used. Instead of water Protogenic solvents and Protophilic solvents are used 1. Protogenic Solvents: These solvents are acidic in properties having high dielectric constant. They are ionized. They liberates ion more than water. Acetic acid, formic acid, propionic acid 2. Protophilic solvents: These solvents are basic in properties having low dielectric constant. They are ionized. They liberates ion less than water. Pyridine, ethylenediamine, dimethyl formamide

22. Precipitation Titration What is Precipitation Titration? Precipitation titration is a type of titration which involves the formation of precipitate during the titration technique. In precipitation titration, the titrant reacts with the analyte and forms an insoluble substance called a precipitate. It continues till the last amount of analyte is consumed. It is used to determine chloride by using silver ions.    Principle of Precipitation Titration  The principle of precipitation titration can be shown as follows –  Quantity of added precipitating reagent = quantity of substance being precipitated 

23. Precipitation Titration Example  Determination of concentration of chloride ions in a solution by using silver ions of a known solution is an example of precipitation titration. Reactions involved are as follows –    AgNO 3 +Cl - AgCl + NO 3 -  (in a solution of NaCl) (White ppt)   Argentometric Titration  It is a type of precipitation titration which involves the use of silver ions. The symbol of silver is Ag which is taken from its Latin name Argentum. So, the word argentometric is also taken from the Latin word Argentum.    Methods of Argentometric Titration Volhard’s Method  Fajan’s Method  Mohr’s Method

24. Sr. No. Volhard’s Method  Mohr’s Method  1. It is an indirect method of titration.  It is a direct method of titration.  2. In this method, red precipitate of ferric thiocyanate is formed which indicates the end point of the titration.  Fe +3 + SCN - FeSCN +2 (Red colored compound) In this method, red precipitate of silver chromate is formed which indicates the end point. 2Ag + + CrO 4 -2 Ag 2 CrO 4 (Reddish Brown ppt) 3. Conditions for titration should be acidic. Otherwise iron ions form hydroxide ions. Conditions for titration should be neutral to alkaline.  4. By this method, we can determine the concentration of halides.  By this method, titration of iodide and cyanate is not possible.  5. This titration is carried out below 20℃ This titration can be carried out under room temperature.