Madsen S, Olgaard K
Clin Chem. 1977;23(4):690-4.
We evaluated a new automatic analyzer for ionized calcium (Ca2+), the Orion Model SS-20, based on a flowthrough ion-exchange electrode. Ca2+ was measured in heparinized whole blood and serum. Within-day variation was 1.2%, day-to-day variation1.6%, and analytical recovery 92.4%. Over the phsiological range interference by K+ and Mg2+ was negligible; major changes in ionic strength, induced by changes in N+ concentration, made correction for a sodium error necessary. Within the physiological range, Ca2+ was inversely correlated to variations in pH. Therefore, to compare Ca2+ values, correction to an apparent pH of 7.40 should be made. The calcium binding effect of heparin was negligible when minimal (4.4 int. units/ml) concentrations of heparin were used. Storage of serum at 4 degrees C for one week resulted in a 4 degrees decrease in apparent serum Ca2+, primarily owing to an increase in pH during storage. In normal material, mean values for blood-and serum-Ca2+(1.10 and 1.07 mmol/liter, respectively) were close to results obtained by previous systems. Errors caused by disturbances in the fluid flow and non-function of half the electrodes we received were the major inconveniences of the analyzer. We conclude that this new analyzer gives decisive advantages in measurement of Ca2+, making this importnant analysis possible as a routine laboratory test for the first time.
我们评估了一种基于流通式离子交换电极的新型离子钙（Ca2+）自动分析仪——奥立龙SS-20型。在肝素化全血和血清中对Ca2+进行了测量。日内变异为1.2%，日间变异为1.6%，分析回收率为92.4%。在生理范围内，K+和Mg2+的干扰可忽略不计；N+浓度变化引起的离子强度的主要变化使得校正钠误差成为必要。在生理范围内，Ca2+与pH值的变化呈负相关。因此，为了比较Ca2+值，应将其校正至表观pH值7.40。当使用最低（4.4国际单位/毫升）浓度的肝素时，肝素的钙结合效应可忽略不计。血清在4℃储存一周导致表观血清Ca2+下降4%，这主要是由于储存期间pH值升高所致。在正常样本中，血液和血清中Ca2+的平均值（分别为1.10和1.07毫摩尔/升）与先前系统获得的结果相近。我们收到的分析仪中流体流动干扰和半数电极失灵所导致的误差是该分析仪的主要不便之处。我们得出结论，这种新型分析仪在Ca2+测量方面具有决定性优势，首次使这项重要分析能够作为常规实验室检测开展。
