Enantioselective high performance new solid contact ion-selective electrode potentiometric sensor based on sulphated γ-cyclodextrin - carbon nano fi ber composite for determination of multichiral drug moxi fl oxacin

Multiple chiral centered drugs not only pose greater risk than single center in asymmetric medium of human bodies but also beneficial to them in many ways. Therefore, online monitoring and rapid chiral sensing method is always desirable for both isomers as well as their impurities. In the present paper, we have developed a new solid-contact ion selective electrode (SC-ISE) for enantioselective recognition of RR and SS moxifloxacin (RR-MX/SS-MX) based on chiral nanocomposite of sulphated gamma-cyclodextrin (S gamma-CD) and carbon nanofibers (CNF) incorporated into a plasticized poly vinyl chloride (PVC) employing potentiometry. CNF are used for the first time to fabricate SC-ISE as the intermediate layer between an ionophore-doped polymeric membrane and a glassy carbon electrode (GC) for MX enantiomers. The host-guest interaction takes place between gamma-CD and RR/SS isomer in the polymeric membrane of the solid-contact electrode forming 1:1 chelate complex where enantioselectivity is achieved in the terms of stability constant (SS MX = 1786 M-1 and RR-MX = 390 M-1 and Gibbs free energy employing square wave voltammetry (SWV). The new electrode displays a Nernstian slope (60.10 +/- 0.25 mV/decade) with the linear range obtained was 1 x 10-2 to 6.5 x 10-7 M and the detection limit of 1.5 +/- 0.16 x 10-7 M. The developed solid-contact electrode shows very small drift in potential (E Delta/t Delta = 154 mu Vh-1) and fast response time of less than 5 s throughout the linear range. The assay of SS-MX in the presence of its antimer RR-MX was carried out using different ratios of both enantiomers, recovery of SS-MX in the presence of RR clearly demonstrate the enantioselectivity and stereospecificity of the proposed SC-ISE. The practical analytical utility of developed chiral potentiometric sensor was demonstrated by measurement of SS-MX in pharmaceutical formulations, urine and blood serum samples. Surface characterization of solid contact electrode was performed using Frequency Response Analyzer (FRA), Scanning electron microscopy (SEM) and the effect of the interfacial water film was evaluated using potentiometric water layer test.