CONSTRUCTION OF A DIFLUNISAL ION SENSOR AND ITS USE IN AUTOMATED FLOW-INJECTION METHODS FOR ASSAY, CONTENT UNIFORMITY, AND DISSOLUTION STUDIES OF FORMULATIONS
P. Solich et al., CONSTRUCTION OF A DIFLUNISAL ION SENSOR AND ITS USE IN AUTOMATED FLOW-INJECTION METHODS FOR ASSAY, CONTENT UNIFORMITY, AND DISSOLUTION STUDIES OF FORMULATIONS, Journal of pharmaceutical sciences, 84(7), 1995, pp. 889-894
A diflunisal ion selective electrode of the PVC membrane type with an
ion-exchanger consisting of the tetraheptylammonium-diflunisal ion pai
r is described. The sensor exhibits a rapid, near-Nernstian, selective
response to diflunisal anion in the pH range 7-10, with a (batch) det
ection limit of 1 x 10(-5) M. The ion sensor was used as a flow detect
or in an automated flow-injection analyzer to develop routine methods
for assays (concentration range 1-50 x 10(-4) M, (flow) detection limi
t 2.6 x 10(-5) M), content uniformity, and dissolution studies of difl
unisal formulations. No serious interference from common ions and tabl
et excipients was found, and the drug can be directly determined in co
lored samples without separation steps. Fourty measurements can be per
formed automatically per hour with a precision of 0.5-1.8% relative st
andard deviation. The automated method for the dissolution test provid
es a complete dissolution profile by the end of the experiment. Using
the constructed ion sensor, the intramolecular hydrogen bonding of the
diflunisal anion was studied, thereby revealing a new application of
ion sensor potentiometry.