Estimation of Ephedrine Hydrochloride

Ephedrine Hydrochloride

Formula : C10H15NO,HCl

Molecular weight : 201.7

Description : Colourless crystals or a white, crystalline powder; odourless. It is affected by light

Molecular structure :

Assay of Ephedrine Hydrochloride

Weigh accurately about 0.17 g of Ephedrine Hydrochloride, dissolve in 10 ml of mercuric acetate solution, warming gently, add 50 ml of acetone and mix. Titrate with 0.1 M perchloric acid, using 1 ml of a saturated solution of methyl orange in acetone as indicator, until a red colour is obtained. Carry out a blank titration.

1 ml of 0.1 M perchloric acid is equivalent to 0.02017 g of C10H15NO,HCl.

= X ml × Normality (Calculated) × 0.02017 × 100/N(Given) × Wt. of sample(in gm)

where

X ml = Volume of titrant consumed at end point

Normality Calculated = Normality of Perchloric acid after standardization

Normality Given = 0.1 N (theoretically)

Preparation and Standardization of 0.1N Perchloric acid

Reagents : Perchloric acid, Glacial acetic acid, Acetic anhydrate, Potassium hydrogen phthalate, crystal violet and water.

Glassware: Volumetric Flask, measuring cylinder, Burette, Conical Flask, beaker and Pipettes.

Preparation:

Gradually mix 8.5 ml of perchloric acid to 900 ml of glacial acetic acid with vigorous and continuous stirring. Now add 30 ml acetic anhydride and make up the volume to 1 liter with glacial acetic acid and allow to stand for 24 hours before use. The acetic anhydride reacts with the water in perchloric acid and some traces in glacial acetic acid thereby making the resulting mixture anhydrous.

Principle

Perchloric Acid is a very strong acid and when it is made to dissolve in acetic acid, the latter can behave as a base and forms an ‘onium ion’ after combining with protons donated by the perchloric acid(HClO4). Thus, we have :

Potassium in the Potassium Hydrogen Phthalate reacts with perchlorate ion(ClO4-) gives KClO4(Potassium perchlorate) and Potassium Hydrogen Phthalate ion.

Potassium Hydrogen Phthalate ion reacts with CH3COOH2⁺ ion (onium ion) converted into Phthalic acid and Acetic acid. in this reaction onium ion donates proton and phthalate ion accepts proton.

Standardization:

Weight accurately about dissolve 0.35 g of potassium hydrogen phthalate in 50 ml of anhydrous acetic acid, warming gently if necessary. Allow to cool protected from the air and titrate with the perchloric acid solution using 0.05 ml of crystal violet solution as indicator. A light green colour is the end point.

Each ml of 0.1M perchloric acid VS is equivalent to 20.42 mg of C8H5KO4. Perform a duplicate and calculate the molarity factor.(MF) Note down the average value .

Calculation

MF = W x actual molarity of perchloric acid / V x 0.02042 (factor)

Where

V = Volume of perchloric acid consumed in ml.

W = Weight of potassium hydrogen phthalate in g.

Example:

V=16 ml

W=0.35014gm

= 0.35014x0.1

16 x0.02042

=0.107168 M

Note :