Bijster P, Vink K L
Clin Chem. 1984 Jan;30(1):6-10.
We measured the emf of NaCl solutions (120-160 mmol/L) with a home-built cell in steady-state and with some commercial direct potentiometric analyzers about 20 s after the sample is introduced into the instrument. We compared the results with the theoretical sodium ion activity calculated according to different thermodynamic theories. The slope of the calibration graph was calculated with and without correction for the influence of NaCl concentration on the liquid junction potential of the calomel reference electrode. We conclude that different theories used to calculate the sodium ion activity in the concentration range investigated give almost the same results; furthermore, introduction of the liquid junction potential leads to a more nernstian-like slope of the calibration graph. Measurement of identical NaCl solutions with various commercial analyzers showed different displayed concentrations, presumably because of differences in junction structure, measuring time, and concentration of calibration solutions.
我们使用自制的电池在稳态下测量了氯化钠溶液（120 - 160 mmol/L）的电动势，并在将样品引入仪器约20秒后，使用一些商用直接电位分析仪进行了测量。我们将结果与根据不同热力学理论计算出的理论钠离子活度进行了比较。在校准曲线斜率的计算中，考虑了和未考虑氯化钠浓度对甘汞参比电极液接电位的影响。我们得出结论，在所研究的浓度范围内，用于计算钠离子活度的不同理论给出的结果几乎相同；此外，液接电位的引入导致校准曲线的斜率更接近能斯特斜率。使用各种商用分析仪对相同的氯化钠溶液进行测量时，显示出不同的浓度，这可能是由于液接结构、测量时间和校准溶液浓度的差异所致。
