TITLE:
Spectrophotometric Study for the Reaction of Pentoxifylline Hydrochloride with 1,2-Naphthoquinone-4-Sulphonate: Kinetics, Mechanism and Application for Development of High-Throughput Kinetic Microwell Assay for Pentoxifylline in Quality Control Laboratory
AUTHORS:
Ashraf M. Mahmoud, Saad A. AlQahtani
KEYWORDS:
Pentoxifylline HCl, 1, 2-Naphthoquinone-4-Sulphonate, Kinetic Spectrophotometry, Pharmaceutical Analysis, Micro-Well Plate Reader
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.7 No.2,
February
2,
2016
ABSTRACT: Spectrophotometric
study was carried out, for the first time, to investigate the reaction between
the vasodilator pentoxifylline hydrochloride (POX) and
1,2-naphthoquinone-4-sulphonate (NQS) reagent. The reaction occurs in alkaline
medium to activate the nucleophilic substitution reaction producing an
orange-colored product measured spectrophometrically at λmax 472 nm. The variables affecting the reaction were
carefully studied and the conditions were optimized. The kinetics of the
reaction was investigated and its activation energy was found to be 0.262
cal/mol. Owing to its low activation energy, the reaction proceeded easily and
was successfully used for simple and rapid assay of POX. The stoichiometry of
the reaction was determined (1:1), and the reaction mechanism was suggested. To
develop a high-throughput methodology used in quality control laboratory, a
comparative study of the reaction using the conventional spectrophotometric
versus microwell assay was applied. Under the optimum reaction conditions, the
initial rate and fixed time methods were utilized for constructing the calibration
graphs for determination of POX concentrations. The linear range was 10 - 120 μg/ml with good correlation coefficients (0.9987 -
0.9998). The LOD was 2.5 and 3.4 μg/ml for initial rate and fixed time methods, respectively. The intra-
and inter-day accuracy and precision of the developed methods were satisfactory,
where RSD was ≤3.94%. The present methods have been successfully applied to the
determination of POX in its pharmaceutical tablets, and the percentage recovery
values were 97.9% - 101.9%. Therefore, we strongly recommend the proposed
methods for determination of POX in quality control laboratories.