NON-AQUEOUS TITRATIONS PART-2; MCQ for GPAT, Pharmacist, NET JRF and GATE

DETECTION OF END POINT :-

• Visual indicator are formed to the most suitable for the detection of end point in non-aqueous Titration
• There are following important indicator are used in non aqueous Titration are as follows :-

1. Indicator :– crystal violet

• composition of indicator W/V :- 0.5% in glacial acetic acid

•colour change :-

1.  Basic :- violet
2. Neutral :- blue – green
3. Acidic :- yellowish- green

2. Indicator :– 1-Naphthol benzenein

• Composition of indicator W/V :- 0.2% -1% glacial acetic acid

•colour change :-

1.  Basic :- blue
2. Neutral :- orange
3. Acidic :- dark green

3.Indicator :- oracet blue B

• composition of indicator W/V :- 0.5 acetic acid

•colour change :-

1.  Basic :- blue
2. Neutral :- purple
3. Acidic :- pink

4. Indicator :- Quinaldine red

• composition of indicator W/V :- 0.1% methanol

•colour change :-

1.  Basic :- magenta
2. Neutral :- –
3. Acidic :- colourless

5. Indicator :- Thymol blue

• composition of indicator W/V :- 0.2 % methanol

•colour change :-

1.  Basic :- yellow
2. Neutral :-
3. Acidic :- blue

Assay by non – aqueous Titration :-

It can be divided into two heads :-

1. Acidimetry :- this can be further divided into two groups

1. Titration of primary, secondary and tertiary amine.
2. Titration of halogen acid salts of bases.

2. Alkalimetry in non aqueous Titration :-

Titration of acidic substance.

• ACIDIMETRY IN NON AQUEOUS TITRATION :-

Example Is primary amine :-

Methodology :-

1. Preparation of 0.1 M perchloric acid
2. Standardization of 0.1 M perchloric acid
3. Choice of indicator
4. Effect on temp. On assay

1.Preparation of 0.1 M perchloric acid :-

• 8.5 ml of perchloric acid (72%w/w) to 500 ml of anhydrous glacial acetic acid with continue & efficient mixing.
• Add 25 ml of acetic & anhydrous and cool
• Add  anhydrous glacial acetic acid to produce 1000 ml.
• Allow it to stand for 24 hour before use.
• Determination the moisture & Acetic anhydride content.
• Water content should not exceed 0.05% add more acetic anhydride.
• If the solution contains no. Titratable water add sufficient water to obtain content of water between 0.02-0.05%.
• Excess acetic anhydride is not always advantageous.
• Care must be taken in case of primary & secondary amine.
• The perchloric acid must be diluted with acetic acid before adding the acetic anhydride failure to observe this precaution leads to formation of explosives acetyl perchlorate.
• Other strength can be prepared by diluting it with anhydrous glacial acetic acid.

STANDARDISATION 0.1 M PERCHLORIC ACID :-

• Alkali & alkali earth metal e.g potassium hydrogen phthalate function as base in acetic acid solution.
• It can be used as primary standard for standardising the acetous perchloric acid

Method :-

• 0.35 g of potassium Hydrogen phthalate previously dried at 120º C for 2 hours.
• Dissolve it in 50 ml of glacial acetic acid.
• Add 0.1 ml of crystal violet solution.
• Titrate with the perchloric acid solution until the violet colour change to green
• Perform the blank & make necessary corrections.

EXAMPLE OF DRUG THAT DETERMINED BY THIS METHOD

MCQ

1. Diazepam is Assay by which method ?

A. Acid base titration

B.Non aqueous titration

C. Karl fischer titration

D. NMR

2. Which indicator give magenta in basic medium ?

A. Quinaldine red

B. 1-Naphthol benzenein

C.Oracet blue B

D.Thymol blue

3. How many percentage of acetic acid in oracet blue B ?

A.0.3% w/v

B.0.5 % w/v

C.0.2%  w/v

D.0.1% w/v

4.Which indicator give  yellow colour in basic medium ?

A. Crystal violet

B. 1-Naphthol benzenein

C.Oracet blue B

D.Thymol blue

5.Pilocarpine nitrate  is Assay by which method ?

A. Acid base titration

B.Non aqueous titration

C. Karl fischer titration

D. NMR

6. How many w/v of methanol present in Quinaldine red ?

A. 0.3

B.0.2

C.0.1

D.0.4

7.Nicotinamide  is Assay by which method ?

a. Acid base titration

b.Non aqueous titration

c. Karl fischer titration

d. NMR

8.Atropine methonitrate  is Assay by which method ?

A. Acid base titration

B.Non aqueous titration

C. Karl fischer titration

D. NMR

ANSWER KEY

1.B

2.A

3.B

4.D

5.B

6.C

7.B

8.B

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REFERENCE :- 

TEXT BOOK OF PHARMACEUTICAL ANALYSIS THIRD EDITIONS BY DR.S.RAVI SANKAR (PG.NO.19.1 TO 19.12)