New cost-effective potentiometric membrane sensors with cylindrical configuration responsive to
ephedrine are described. The sensors setup is, based on the use of triacetyl-b-cyclodextrin [(triacetyl-bCD)]
as a neutral ionophore embedded in a plasticized poly (vinyl chloride) (PVC) matrix (sensor I) and
carboxylated poly(vinyl chloride) [(PVC–COOH)] as a simultaneous plastic matrix and ion exchanger
(sensor II). Both sensors showed significant enhancement of response towards ephedrinium cation
(EPDþ) over a concentration range of 3.0 105
–8.0 103 mol L1 at pH 4–9 and 3–8 with low
detection limits of 5.7 106 and 6.2 106 mol L1 for sensors (I) and (II), respectively. The sensors
displayed near-Nernstian cationic slope of 57.0 and 55.6 mV decade1 for EPDþ and the effects of
lipophilic salts and various foreign common ions were examined. The sensors were also satisfactorily
used as tubular detectors in a double channel flow injection system. The intrinsic characteristics of the
detectors in a low dispersion manifold under hydrodynamic mode of operation were determined and
compared with data obtained under batch mode of operation. Validation of the method revealed good
performance characteristics including long life span, good selectivity for EPDþ over a wide variety of
other organic compounds, long term stability, high reproducibility, fast response, low detection limit,
wide measurement range, acceptable accuracy and precision. Applications of the sensors to the
determination of EPDþ in pharmaceutical formulations and spiked biological fluid samples were
carried out and compared with standard techniques. Notably, the sensors introduced offer several
advantages over many of those previously described that are amenable to quality control/quality
assurance assessment of the homogeneity, stability and purity of ephedrine drug tablets.
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