Kruse-Jarres J D
Institute for Clinical Chemistry, Katharinenhospital, Stuttgart, FRG.
Med Prog Technol. 1988;13(3):107-30.
Ion-selective potentiometry is used more and more in clinical medicine for the determination of electrolytes in various body fluids. With regard to K+, Na+, Ca2+ and Cl- this technique has almost completely displaced flame photometry, atomic absorption spectrophotometry and coulometry. Moreover, reliable automated devices have facilitated routine analyses. Until now there are 6 different types of ion-selective sensors: glass membrane, solid phase, fluid membrane, carrier, gas-sensitive, and enzyme electrodes with immobilized enzymes. The latter are particularly used for in vivo monitoring, especially for continuous blood glucose monitoring. The essential fields of application in the clinical laboratory are the determinations of the cations H+, K+, Na+, Ca2+, Mg2+ and NH3+, and the anions F-, I-, Br-, Cl- and HCO3-. Despite the wide-spread application of ion-selective potentiometry a number of disturbing factors have to be taken into account by the user as well as by the manufacturer in order to get satisfactory results. For instance, there are differences between direct and indirect potentiometry. Moreover, the activities measured cannot be extrapolated readily to the desired concentrations. A careful and accurate calibration, a suitable sample preparation and an adjustment of the measuring conditions to the characteristics of the specimen and the matrix of the sample is necessary before each measurement. Therefore, a consequent internal and external quality control is necessary to achieve an optimal quality of these methods determining vital parameters in medicine. Thus, the technique of ion-selective potentiometry represents an important milestone in clinical chemistry. Moreover, being a very rapid procedure it is indispensable to clinical diagnostics.
离子选择性电位分析法在临床医学中越来越多地用于测定各种体液中的电解质。对于钾离子（K⁺）、钠离子（Na⁺）、钙离子（Ca²⁺）和氯离子（Cl⁻），该技术几乎已完全取代了火焰光度法、原子吸收分光光度法和库仑法。此外，可靠的自动化设备促进了常规分析。到目前为止，有6种不同类型的离子选择性传感器：玻璃膜、固相、液膜、载体、气敏和固定化酶的酶电极。后者特别用于体内监测，尤其是连续血糖监测。临床实验室的主要应用领域是测定阳离子氢离子（H⁺）、钾离子（K⁺）、钠离子（Na⁺）、钙离子（Ca²⁺）、镁离子（Mg²⁺）和铵离子（NH₃⁺），以及阴离子氟离子（F⁻）、碘离子（I⁻）、溴离子（Br⁻）、氯离子（Cl⁻）和碳酸氢根离子（HCO₃⁻）。尽管离子选择性电位分析法应用广泛，但用户和制造商都必须考虑许多干扰因素，以便获得满意的结果。例如，直接电位法和间接电位法之间存在差异。此外，测得的活度不能轻易外推到所需的浓度。在每次测量之前，需要进行仔细而准确的校准、合适的样品制备，并根据样品的特性和基质调整测量条件。因此，必须进行严格的内部和外部质量控制，以实现这些测定医学重要参数方法的最佳质量。因此，离子选择性电位分析技术是临床化学中的一个重要里程碑。此外，作为一种非常快速的方法，它对临床诊断不可或缺。
