不同pH值羟基乙叉二膦酸的制备和光谱分析研究

羟基乙叉二膦酸受pH值影响很大.以质量分数为25%的NaOH溶液为滴定剂,制备pH值为2~13的羟基乙叉二膦酸(HEDP),研究了各pH值时HEDP的红外光谱,用拉曼光谱、等离子体发射光谱进行验证.光谱研究结果显示,pH值=2时主要是以羟基乙叉二膦酸存在,随着pH值升高,羟基乙叉二膦酸依次以一钠盐、二钠盐、三钠盐、四钠盐存在;816cm-1δOH吸收峰和630cm-1υP-C吸收峰是羟基乙叉二膦酸及其钠盐的特征吸收峰,α位碳的羟基变形振动吸收不变,和氧相连的υP-C随pH值升高吸收波数逐渐增大.

1-Hydroxy Ethylidene-1,1-Diphosphonic Acid at Different pH Values:Preparation and Spectra Analyses

1-Hydroxy ethylidene-1,1-diphosphonic acid(HEDP)is much affected by pH values.In the present paper,HEDP was prepared at different pH values ranging from 2to 13,by NaOH solution with 25% of mass fraction as titrant.The FTIR spectra of HEDP at different pH values were studied and validated by Raman and plasma emission spectroscopy.The results show that HEDP is the main product at pH=2while its monosodium,disodium,trisodium and tetrasodium salts exist in turn with increasing pH;theδOHband at 816cm-1 andυP-Cband at 630cm-1 are the characteristic bands of HEDP and its sodium salt.In addition,the deformation vibration band ofδOHband atαposition remains unchanged whereas the intensity ofυP-C band attached to oxygen increases gradually with increasing pH values.