Page 56 - PC 101 practical notes 24-25..

MANSOURA NATIONAL UNIVERSIY
PHARM D- CLINICAL PHARMACY LEVEL I PHARM. ANAL. CHEM. I (PC 101)

C Ca al lc cu ul la at ti io on ns s : :

1 st standard
Aspirin (sample)
NaOH + HCl ⎯→⎯ NaCl + H 20
nd standard
2

The equivalence factor (F) can be calculated on NaOH (1 stand.) or on HCl
st
(2 stand.) but it is preferred to be calculated on the 1 standard.
nd
st
Calculation of equivalence factor (F):

2 NaOH ≡ 1 Aspirin
standard sample

1
 1 NaOH ≡ Aspirin
standard 2 sample

1 x M.W. of Aspirin x 0.1

each ml of 0.1 N NaOH ≡ 2 ≡ .......... g Aspirin
1 x 1000

Calculation of concentration:

(Blank reading – E.P.) x F x 1 10 00 0
Concn. (Purity) of Aspirin = = ........ g g% %
0 0. .3 32 20 0

Results:

E.P. =

Concn. (Purity) of Aspirin =

The Pharmacopoeial limits for the purity of aspirin:

→ According to BP 2007: from 95.0% to 105.0%.

→ According to USP 2007: from 90.0% to 110.0%.

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