A neutral ligand ion-exchanger type of ion-selective electrode is used in the current version of the Orion Model SS-20 calcium analyzer. We evaluated it over the pH range 4.0 to 8.5, using albumin solutions containing 150 mmol/L NaCl and pooled patients' serum. Within this pH range response was nernstian, and the relationship between potential (in millivolts) and log [Ca2+] at each pH was linear. Variation in Ca2+ with increasing ionic strength (because of added NaCl) was not significantly different between standards and albumin solutions; it decreased in both. In contrast, the proportion of calcium in serum increased with increasing NaCl concentrations. Ca2+ was not bound in whole serum albumin at a pH less than about 3.9. We observed a substantial difference between the degree of Ca2+ binding in solutions of fatty-acid-free human albumin and serum.
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机译：当前版本的Orion Model SS-20钙分析仪使用中性配体离子交换剂类型的离子选择电极。我们使用包含150 mmol / L NaCl的白蛋白溶液和合并的患者血清在4.0至8.5的pH范围内对其进行了评估。在此pH范围内，响应是神经性的，并且每个pH下的电势（以毫伏为单位）和log [Ca2 +]之间的关系是线性的。随着离子强度的增加（由于添加了NaCl），Ca2 +的变化在标准溶液和白蛋白溶液之间没有显着差异。两者都减少了。相反，血清中钙的比例随NaCl浓度的增加而增加。在小于约3.9的pH值下，Ca2 +未结合在全血清白蛋白中。我们观察到在不含脂肪酸的人白蛋白和血清溶液中Ca2 +结合程度之间存在实质性差异。
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