Novel All-solid-state (ASS) Polymeric-Membrane-Sensor (ASS-PME) for Diltiazem and Its Application

Diltiazem (DZ) is a common benzodiazepine family, which is a calcium channel blocker usually supplied and used as a hydrochloride salt. The widespread use of the pharmaceutical has naturally created an increasing need for its analysis. It is therefore the main objective of the present work to develop an all-solid-state (ASS) polymeric-membrane-electrode (PME) for the analysis of DZ hydrochloride in pharmaceutical formulations. The developed ASS-PME is based on the application of an ion-pair agent in its sensing element. Experiments showed that the optimal results could be achieved with a PME containing 10% wt. of the ion-pair agent (i.e. DZ-tetrakis (p-chlorophenyl) borate (TPClPB)), 56% wt. of dibutyl phthalate (DBP) as the membrane solvent, 30% wt. of polyvinyl chloride (PVC), and 4% wt. of a room temperature ionic liquid (RTIL). Next the polymeric membrane was coated on an ASS element made of a composite of an epoxy resin, graphite and multiwalled carbon nanotubes (MWCNTs) which was deposited on a copper wire, as the internal contact. The DZ-ASS-PME revealed a potential response of 56.8±0.3 mV/decade over a wide concentration range of 2.0×10-7 to 1.0×10-3 M and was found to be suitable for applied to the analysis of DZ, as proved by the application of the ASS-PME in the measurement of DZ concentration in DZ tablets.