Development of a potentiometric sensor for determination of active substance in h2-receptor antagonist guanidine structured drugs, investigation of its applicability in ulcer and gastric protective drug formulations

Guanidine is an alkaline molecule formed by the attachment of three amino groups to a single carbon atom. In pharmacological forms, molecules containing guanidine, or its derivatives are commonly used as active agents. Guadinine derivatives, acting as H2-receptor antagonists, offer effective treatments for gastric disorders. This thesis focuses on developing a guanidine-selective potentiometric sensor by investigating the affinity of various guanidine derivatives used in commercial pharmaceuticals. The sensor composition exhibiting the best potentiometric performance consisted of a membrane composition by weight of 4.0% ionophore, 32.0 % PVC (polyvinylchloride) and 64.0 % o-NPOE (ortho-nitrophenyl octylether). The sensor demonstrated a linear working range from 1.0 × 10-5 to 1.0 × 10-1 molL-1 with an R2 value of 0.9978, a detection limit of 5 µmol/L, and an average response time of 4 seconds. It maintained stable performance across a temperature range of 15-40°C and a pH range of 5.0-9.0. The sensor remained operational for approximately 11 weeks without significant deviation in potential responses. In application, the sensor successfully measured guanidine content with high recovery rates in various samples, including commonly used gastric protective pharmaceuticals. The high repeatability and stable potentiometric responses of the developed sensor demonstrate its potential as a reliable alternative method for the determination of guanidine in analytical chemistry.