Abstract
An ion-selective electrode is proposed for the rapid determination of ceftriaxone (Ceftr) in biological samples. The ion-pair of octadecylamine (ODA) with ceftriaxone is a ionophore of the ceftriaxone-selective electrode (Ceftr-ISE) membrane. To elucidate the membrane’s operation mechanism, we investigated equilibria in the membrane–solution system as functions of medium acidity and ionophore concentration. At pH values ranging from 6 to 9, the ion pair (ODA) \(_{2}^{ + }\) ·Ceftr2– remains stable, and the membrane responds selectively to ceftriaxone. The optimal membrane composition for the Ceftr-ISE was determined as follows (wt %): (ODA) \(_{2}^{ + }\) ·Ceftr2– 0.80, polyvinyl chloride 33.06, ODA 1.7 (100 mM), dioctyl sebacate 66.14. The internal electrolyte consisted of Ceftr (0.01 M) and KCl (0.01 M). The electrochemical performance of the Ceftr-ISE membrane was characterized by a linear response range from 1 × 10–5 to 0.1 M, electrode slope of 24.9 mV per decade, and limit of detection of 8.3 × 10–6 M. Potentiometric selectivity coefficients of the Ceftr-ISE were determined using the separate solution method. The electrode enabled the determination of Ceftr in blood and saliva samples from COVID-19 patients. The accuracy of Ceftr quantification was validated using the standard addition method.
