Ion selective electrode (in-line analyzer) versus UV-spectroscopy (at-line analyzer); which strategy offers more opportunities for real time monitoring of the degradation kinetics of pyridostigmine bromide

Pharmaceutical product quality is of vital importance for the patients' safety. In spite of the long history of development of spectroscopic methods for monitoring pharmaceutical products degradation kinetics; this work investigates the opportunities offered by electroanalytical methods (particularly, ion selective electrodes) for in-line monitoring the degradation kinetics compared to at-line monitoring offered by conventional spectroscopic methods. For a meaningful comparison, pyridostigmine bromide (PB) was chosen as hydrolysable anti-cholinesterase drug and two novel strategies for monitoring of PB degradation kinetics catalyzed by hydroxyl ions are presented. The first strategy is achieved by continuous measurement of the decrease in the produced emf over time by incorporation of an in-site PB selective electrode constructed using PVC membrane containing calix[6]arene as an ionophore. The second strategy utilizes UV spectrophotometry for at-line tracking of either the decrease of PB peak at 269 nm or the increase of THMP peak at 320 nm over time. The use of these new methods provides real time observation and yields a continuous profile of the hydrolysis behavior of PB under various pH and temperature conditions. Moreover, a great advantage of these proposed in- and at-line systems is their higher accuracy for rate constant estimation relative to other off-line methods. (C) 2015 Elsevier B.V. All rights reserved.