对乙酰基偶氮胂光度法测定粮食中的钙

粮食中钙的测定一般采用EDTA滴定法和原子吸收法。前者难应用于微量分析,后者则需要贵重的仪器。变色酸双偶氮衍生物光度法可以克服二者的缺点。这方面的研究已见报导。但仍有一些干扰离子的问题须待解决。我们曾研究过对溴偶氮胂在强碱性条件下测定土壤中的钙,避免了镁离子的干扰。本文报导对乙酞基偶氮肿在强碱性条件下测定粮食中的钙,Mg²⁺和许多重金属离子无干扰,不需分离操作,方法简捷。

SPECTROPHOTOMETRIC DETERMINATION OF CALCIUM IN GRAIN WITH p-ACETYL-ARSENAZO

P-Acelyl-arsenazo reacts with calcium cation at pH=12.9, forming a dark-blue complex with maximum absorption at 640 nm. The molar extinction coefficient of the complex is 1.1×10⁴. The relationship between the absorption and the concentration of the solution obeys the Beer's law, provided that Ca²⁺ has the concentrations within 5-50μg/25ml.The interference of Fe³⁺ and Cu²⁺ can be eliminated by adding F^- and triethanolamine,respectively. The recovery of Ca²⁺ added into the solutions of digested grains varys in the range of 95-110%.