Determination of the Antiretroviral Drug Lamivudine by Potentiometric Titration using All Solid State Graphite Based Iodide Selective Electrode
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Date
2010-07
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Addis Ababa Universty
Abstract
A solid-state iodide selective electrode with Ag2S-AgI adsorbed on graphite rod, recovered from a
dry cell, was prepared and validated for its typical response characteristics with an objective to
develop a potentiometric titration system for rapid measurements of Lamuvidine (LMV) in
tablets used as an antiretroviral drug for Hepatis B and HIV patients. The partial validation
exhibited typical response values of linear range of 10-6 to 10-1 M iodide and a slope
57.57 mV/decade which reasonably agreed with early data from this Laboratory. The basis of
LMV determination is its oxidation by excess bromine generated from bromate-bromide mixture.
The unreacted bromine oxidized the added excess iodide to iodine. The amount of bromine
consumed by LMV, the basis of its determination, was determined by subtracting the back-titrated
iodine with thiosulphate whose end-point was located potentiometrically with the solid state iodide
selective electrode against a reference electrode. The iodometric back titration provided for the
indirect determination of 1-30 mg LMV in turbid tablet test solutions. There was no interference
from the excipients in the tablet and this provided for LMV assays with and without filtration of
the turbid (insoluble) pharmaceutical excipients. Acid concentrations between 0.2 – 1.5 M HCl
did not have any influence on the titration end-points. The intra-day and inter-day variation of the
result was not significant. The system recovery for standard added sample was 99.3 ± 5.3 % and
for a reference LMV was 98.4 ± 0.8 %. For quality control checks, the potentiometric backtitration
method was favorably compared with an independently applied reference test method (UV
spectrophotometry at 280 nm), by quantitating LMV in a blind sample and reference drug material.
This inexpensive potentiometric titration system was easy to operate and exhibited good recovery
for LMV determinations in the typical drug dose labeled to contain 150 mg per tablet.
Key words: Antiretroviral Drug LMV; ISE method; Potentiometric Titration; Bromate-Bromide
Mixture; Iodometric Back Titration
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Keywords
Antiretroviral Drug LMV, ISE method, Potentiometric Titration, Bromate-Bromide Mixture, Iodometric Back Titration