Mostafa Gamal Abdel-Hafiz, Ghazy Shaban el-Syed
Microanalytical Lab., Applied Organic Chemistry Department, National Research Center, Dokki, Cairo, Egypt.
Ann Chim. 2003 Jul-Aug;93(7-8):691-9.
The construction and general performance characteristics of two novel potentiometric PVC membrane sensors responsive to the pyridoxine hydrochloride known as vitamin B6 (VB6) are described. These sensors are based on the use of the ion-association complexes of the pyridoxine cation with phosphomolybdate, and phosphotungstate counter anions as ion pair in a plasticized PVC matrix. The electrodes show a stable, near-Nernstian response for 6x10(-5)-1x10(-2) M VB6 at 25 degrees C over the pH range 2-4 with a cationic slope of 54.0+/-0.5 and 54.5+/-0.4 per concentration decade for pyridoxine-phosphomolybdate and pyridoxine-phosphotungstate respectively. The two electrodes have the same lower detection limit (4x10(-5) M) and the response times are 45-60 and 30-45 s in the same order for both. Selectivity coefficients for VB6 relative to a number of interfering substances were investigated. There is negligible interference from many cations, some vitamins and pharmaceutical excipients. Direct potentiometric determination of 15-2000 microg/ml pyridoxine shows an average recovery of 98.0% and 99.0% with relative standard deviation 1.5% and 1.2% at 100.0 microg/ml for pyridoxine-phosphomolybdate and pyridoxine-phosphotungstate electrodes, respectively. The determination of VB6 in some pharmaceutical preparations using the proposed electrodes gave an average recovery of 98.0 and 99.0% of the nominal value and a mean standard deviation of 1.1% and 0.9% (n=10) for pyridoxine-phosphomolybdate and pyridoxine-phosphotungstate electrodes, respectively. The results compare favorably with data obtained by the British Pharmacopoeia method.
本文描述了两种新型电位型PVC膜传感器的构建及其一般性能特征，这两种传感器对盐酸吡哆醇（即维生素B6，VB6）有响应。这些传感器基于吡哆醇阳离子与磷钼酸盐和磷钨酸盐抗衡阴离子形成的离子缔合物，将其作为离子对用于增塑PVC基质中。在25℃、pH值为2 - 4的范围内，对于6×10⁻⁵ - 1×10⁻² M的VB6，电极呈现稳定的近能斯特响应，吡哆醇 - 磷钼酸盐和吡哆醇 - 磷钨酸盐电极每浓度 decade 的阳离子斜率分别为54.0±0.5和54.5±0.4。这两种电极具有相同的较低检测限（4×10⁻⁵ M），响应时间顺序相同，分别为45 - 60秒和30 - 45秒。研究了VB6相对于多种干扰物质的选择性系数。许多阳离子、一些维生素和药用辅料的干扰可忽略不计。直接电位法测定15 - 2000 μg/ml的吡哆醇，吡哆醇 - 磷钼酸盐和吡哆醇 - 磷钨酸盐电极在100.0 μg/ml时的平均回收率分别为98.0%和99.0%，相对标准偏差分别为1.5%和1.2%。使用所提出的电极测定一些药物制剂中的VB6，吡哆醇 - 磷钼酸盐和吡哆醇 - 磷钨酸盐电极的平均回收率分别为标称值的98.0%和99.0%，平均标准偏差分别为1.1%和0.9%（n = 10）。结果与英国药典方法获得的数据相比具有优势。
