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5-Br-PADAP光度法分别测定铬和钴已有报道。铬(Ⅲ)水合物为惰性配合物,它的显色反应通常需在加热时进行,而钴与5-Br-PADAP在弱酸性介质中形成非常稳定的钴(Ⅲ)的配合物,采用酸化或加掩蔽剂的方法均不能破坏,故钴的存在对5-Br-PADAP光度法测定铬有严重干扰。我们利用铬、钴与5-Br-PADAP显色反应的这两个特点,研究了非离子表面活性剂OP-5-Br-PADAP光度法联合测定钴和铬的方法。即在室温时测定钴的吸光度A_1,此时铬不显色不干扰钴的测定;在加热时使铬与5-Br-PADAP发生反应,测定钴和铬的总吸光度A_2,然后由A_2-A_1可求得铬的吸光度。本法选择性好,灵敏度高,方法简单。
5-Br-PADAP spectrophotometric determination of chromium and cobalt have been reported. Chromium (Ⅲ) hydrate is an inert complex, its color reaction usually takes place when heating, and cobalt and 5-Br-PADAP form a very stable cobalt (Ⅲ) complex in weakly acidic medium. Acidification Or masking agent methods can not be destroyed, so the presence of cobalt on the 5-Br-PADAP spectrophotometric determination of chromium have serious interference. We use the two characteristics of chromogenic, cobalt and 5-Br-PADAP color reaction to study the non-ionic surfactant OP-5-Br-PADAP spectrophotometric method for the determination of cobalt and chromium. That is, the absorbance A 1 of cobalt is measured at room temperature, and the determination of cobalt does not interfere with the determination of chromium when it is not in color. When chromium and 5-Br-PADAP are reacted during heating, the total absorbance A 2 of cobalt and chromium is measured, Chromium absorbance can be obtained. The law of selectivity, high sensitivity, the method is simple.