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钒、钛、锰、铬等元素,对EDTA容量法测定铝、钙、镁,都有不同程度的干扰。高镁低钙、高钙低镁及低钙镁试样,由于待测元素之间含量悬殊较大,对测定会引起干扰。因此,弄清各类试样的干扰情况,是选择分离干扰元素方法及拟定测定方法的基础。 一、干扰元素对测定铝、 钙、镁的影响 钛和铝在一定条件下同时和EDTA络合,又同时被氟盐释放,因而,钛定量干扰铝的测定。当PH=10,用EDTA滴定镁时,微克量的钛就能使铬黑T指示剂封闭。当钛含量高时,由于水解产生的沉淀吸附钙离子而使结果偏低。五价钒与PAN或二甲酚橙指示剂生成红色络合物,当V_2O_5高于0.5毫克时,终点难于判断。
Vanadium, titanium, manganese, chromium and other elements of the EDTA volumetric method for the determination of aluminum, calcium, magnesium, have different levels of interference. High magnesium low calcium, high calcium and low magnesium and low calcium and magnesium samples, due to the large difference between the content of the elements to be measured, the determination will cause interference. Therefore, to understand the interference of various types of samples is to choose the method of separation of interfering elements and to develop the basis for determination. First, the interference elements on the determination of aluminum, calcium and magnesium Titanium and aluminum under certain conditions at the same time and EDTA complexation, but also by the release of fluoride salts, thus, titanium quantitative interference with the determination of aluminum. When pH = 10, titration of magnesium with EDTA, micrograms of titanium can make chromium black T indicator closed. When the content of titanium is high, the result is low due to the adsorption of calcium ions by the precipitate produced by hydrolysis. Pentavalent vanadium and PAN or xylenol orange indicator red complex formation, when the V_2O_5 is higher than 0.5 mg, the end point is difficult to judge.