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测微量钙镁的显色反应近年来有不少报道。我们用DBC-偶氮氯膦作了试验,发现它是钙、镁的良好显色剂,在pH8.0～9.2的硼酸盐缓冲溶液中,钙和镁均与试剂生成蓝色络合物,摩尔吸光系数分别为ε’CaR_2=1.9×10~4、ε′MgR_2=1.1×10~4。络合物形成迅速,可在室温稳定24小时。虽然钙与试剂显色灵敏度低于偶氮氯膦Ⅲ(6.8×10~4),镁与试剂灵敏度低于偶氮氯膦Ⅰ(1.85×10~4),但本法选择性好,不仅可同时测定微量钙、镁,还可通过掩蔽镁而直接测定高镁试样中低含量钙。我们用于同时直接测定结晶硅中微量钙、镁和测定菱镁矿、镁石等高镁试样中低量钙,均获满意结果。
In recent years, many reports have been reported on the color reaction of trace calcium and magnesium. We used DBC-chlorophosphonazo test and found that it is a good color reagent of calcium and magnesium, borate buffer solution pH8.0 ~ 9.2, calcium and magnesium are generated with the reagent blue complex , The molar absorptivities were ε’CaR_2 = 1.9 × 10 ~ 4, ε’MgR_2 = 1.1 × 10 ~ 4, respectively. The complex formed rapidly and was stable at room temperature for 24 hours. Although the sensitivity of calcium and reagent is lower than that of chlorophosphonazo Ⅲ (6.8 × 10 ~ 4) and the sensitivity of magnesium and reagent is lower than that of chlorophosphonazo Ⅰ (1.85 × 10 ~ 4), the selectivity of this method is good not only Simultaneous determination of trace amounts of calcium and magnesium, but also direct determination of low levels of calcium in high-magnesium samples by masking magnesium. We are used to determine the trace calcium and magnesium in crystalline silicon and the low calcium in high magnesium samples such as magnesite and brucite directly.