Alçada M N, Lima J L, Montenegro M C
Physical Chemistry Department, Faculty of Pharmacy, Porto-Portugal.
J Pharm Biomed Anal. 1992 Oct-Dec;10(10-12):757-61. doi: 10.1016/0731-7085(91)80076-l.
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).
本文描述了一种基于离子缔合萃取体系、对麻黄碱有响应的无内参比溶液的PVC膜电极。它将麻黄碱-四（4-氯苯基）硼酸离子对配合物包含于2-硝基苯基辛醚中。所制备的电极在pH为2.5 - 9的溶液中，对2×10⁻⁵ - 10⁻¹ M麻黄碱浓度范围呈现近能斯特响应（每十倍浓度变化57.5 mV）。在至少6个月的时间里，电极电位的重现性日间为±1 mV。对于10⁻⁵至10⁻¹ M之间的麻黄碱浓度，响应时间约为6 s。通过直接电位法对药物制剂（片剂、滴鼻剂和糖浆剂）中麻黄碱的测定，平均回收率为99.1%（w/w），平均标准偏差为1.9%（w/w）。
