Tow simple, accurate and sensitive spectrophotometric methods are
proposed for the determination of imipramine-HCl in pure form and in
pharmaceutical tablets. The first method is based on the formation of
charge-transfer complexes between the drug base as an n-donor and 2,3-
dichloro-5, 6-dicyano-p-benzoquinone (DDQ), p-chloranilic acid (p-CA)
and p-chloranil (p-CL) as Π-acceptors. The colored products are measured
spectrophotometrically at 450, 500 and 540nm for DDQ, p-CA and p-CL,
respectively.
Beer’s law is obeyed in a concentration range of 8-70 μg/ml for the
complex with DDQ and 10-50μg/ml for both complexes with p-CA and p-
CL. The molar absorpitivites are found to be 3.945x103, 1.67x103 and
0.323x103 l.mol-1 cm-1 for DDQ, p-CA and p-CL, respectively.
The second method is based on the extraction of the formed ion –
association complexes of the drug with either thymol blue or bromophenol
blue at pH values 4.16 and 3.60, respectively.
The products exhibit absorption maxima at 415 and 410nm for thymol
blue and bromophenol blue, respectively. Beer’s law is obeyed in a
concentration range of 50-250 and 20-60μg/ml with molar absorpitivites of
0.7795x103 and 1.742x103 l.mol-cm-1 for thymol blue and bromophenol
blue, respectively. |