Garcia Carlos Alexandre Borges, Júnior Laércio Rover, Neto Graciliano de Oliveira
Department of Chemistry, UFS, 49100-000, São Cristóvão, SE, Brazil.
J Pharm Biomed Anal. 2003 Feb 5;31(1):11-8. doi: 10.1016/s0731-7085(02)00598-8.
A simple and rapid method was developed for the K(+) ions determination employing a flow injection system using a flow-through electrode based on the naturally-occurring antibiotic ionophore nonactin occluded in a polymeric membrane. The nonactin ionophore was trapped in poly(ethylene-co-vinyl acetate) (EVA) matrix (40% w/w in vinyl acetate) and dispersed on the surface of a graphite-epoxy tubular electrode. The plasticizer-free all-solid-state potassium-selective electrode showed a linear response for K(+) concentrations between 5.0 x 10(-5) and 5.0x10(-2) M (r=0.9995) with a near-Nernstian slope of 51.5 mV per decade, when Tris-HCl buffer (pH 7.0;0,1 M) was employed as a carrier. The potentiometric-FIA system allows an analytical frequency of 120 samples per hour with a precision of 3.6%. The relative standard deviations (R.S.D.) for K(+) determination in pharmaceuticals samples, without any previous treatment, were lower than 4.0%, comparable to those obtained by flame photometry. Ammonium is the main analytical interference and the electrode response time was 5 s at 25 degrees C. The useful lifetime of the tubular sensor is longer than 3 months in continuous use.
开发了一种简单快速的钾离子测定方法，该方法采用流动注射系统，使用基于包裹在聚合物膜中的天然抗生素离子载体缬氨霉素的流通电极。缬氨霉素离子载体被困在聚（乙烯 - 醋酸乙烯酯）（EVA）基质（醋酸乙烯酯中40% w/w）中，并分散在石墨 - 环氧管状电极表面。无增塑剂的全固态钾选择性电极在使用Tris - HCl缓冲液（pH 7.0；0.1 M）作为载体时，对钾离子浓度在5.0×10⁻⁵至5.0×10⁻² M之间呈现线性响应（r = 0.9995），每十倍浓度变化的斜率接近能斯特斜率，为51.5 mV。电位 - 流动注射分析系统每小时可分析120个样品，精密度为3.6%。未经任何预处理的药物样品中钾离子测定的相对标准偏差（R.S.D.）低于4.0%，与火焰光度法获得的结果相当。铵是主要的分析干扰物，在25℃时电极响应时间为5 s。管状传感器连续使用的有效寿命超过3个月。
