偶氮氯膦Ⅲ分光光度法测定硅钙钡合金中钡含量

Spectrophotometric Determination of the Ba Content in Si-Ca-Ba Alloy by Using Chlorophosphonazo as the Spectral Chromogenic Reagent

研究了偶氮氯膦Ⅲ与钡（Ⅱ）的显色反应及共存离子对该显色反应的影响。结果表明，在pH值为10．0的氨水-氯化铵缓冲溶液中，钡与偶氮氯膦Ⅲ显色剂形成稳定的绿色络合物，该络合物最大吸收波长为670nm，表观摩尔吸光系数为6．49×10^4L／（mol·cm）；在25mL试样溶液中钡量为0～50μg时，吸光度测定符合比尔定律，且具有很高的灵敏度；样品中铝、铁对钡测定的干扰通过加入三乙醇胺和邻菲罗啉来掩蔽，钙的干扰则加入EGTA—Pb来掩蔽。偶氮氯膦Ⅲ分光光度法可用于测定硅钙钡合金中的钡含量，测定结果与认定值相符，且相对标准偏差（RSD）小于2％。

The eolour reaction of chlorophosphonazo with barium（ Ⅱ ） was studied. And the effects of the coexistent ions on the colour reaction were also investigated. The results show that the chromogenic reagent （chlorophosphonazo） reacts with barium to form a stable green complex in NH3 · H2O-NH4Cl buffer solution of pH10.0. The complex exhibits an absorption maximum at 670 nm with an apparent molar absorptivity of 6.49 × 10^4 L/（mol · cm）. The spectrophotometric determination is of high sensitivity obeying Beer＇s law,when 25 mL sample solution contains 0450 μg barium. The disturbance of Ba determination from Al and Fe can be sheltered by adding triethanolamine and 1,10-phenanthroline monohydrate, and Ca disturbance by adding EGTA-Pb. The Ba content in Si-Ca-Ba alloy can be determined by spectrophotometry with chlorophosphonazo,where the determined result is in good agreement with the certified value and the relative standard deviation （RSD） is less than 2 %.