PVC membrane electrode without inner reference solution for the direct determination of ephedrine in pharmaceutical preparations.
A PVC membrane electrode, without inner reference solution, based on an ion association extraction system responding to ephedrine is described. It incorporates an ephedrine-tetrakis (4-chlorophenyl)borate ion-pair complex in 2-nitrophenyloctyl ether. The prepared electrode exhibits a near Nernstian response (57.5 mV per decade) over the concentration range of 2 x 10(-5)-10(-1) M ephedrine in solutions of pH 2.5-9. The reproducibility of the electrode potentials were +/- 1 mV by day during at least 6 months. Response time was about 6 s for ephedrine concentrations between 10(-5) and 10(-1) M. Determinations of ephedrine in pharmaceutical preparations (tablets, nasal drops and syrups) by direct potentiometry gave an average recovery of 99.1% (w/w) and a mean standard deviation of 1.9% (w/w).
Alçada
M N
MN
Physical Chemistry Department, Faculty of Pharmacy, Porto-Portugal.
Lima
J L
JL
Montenegro
M C
MC
D002626:Chemistry, Pharmaceutical / Q000379:methods*; D004304:Dosage Forms; D004566:Electrodes; D004809:Ephedrine / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D011143:Polyvinyl Chloride / Q000737:chemistry; D011199:Potentiometry; D012015:Reference Standards; D015203:Reproducibility of Results
D004304:Dosage Forms; D011143:Polyvinyl Chloride; D004809:Ephedrine