摘要
测量酸碱指示剂水溶液电离平衡体系的紫外可见吸收光谱,酸式与碱式最大吸收峰严重重叠。高斯多峰拟合技术实现酸式和碱式重叠峰的分峰拟合,给出2个吸收峰的积分强度及相应最大吸收波长等光谱参数,进而计算指示剂水溶液酸离解常数pKa。模拟计算结果还证实:随着pH值增加,指示剂碱式峰和酸式峰分别发生显著蓝移和红移,讨论了由此引起的系统测量误差。改进的pKa分光光度测量方法测量步骤和数据处理过程更简单、更具有普适性,结果也更可靠。
UV-visible electronic absorption spectra of acid-base indicator aqueous solutions are measured and characterized by the overlap of the acidic and basic species. A multi-peaks Gaussian fitting technique is used to interpret the spectra and gives spectroscopic shape line parameters such as relative integrated absorbance A1/ A2,maximum absorption wavelengths which are used to calculate the acidic dissociation constants （pK.）. The chi＇2 and R-2 values reached 0. 998 and 10-5 , 10 6 , respectively. The red shift of Xmax for acidic species and the blue shift of h for basic species which causes about ＋3 - 5% systematic error for pKa measurement higher than true value are also observed. The improved experimental procedure for determination of pKa of acid-base indicator is simpler, more reliable and more universal than that in traditional single-wavelength spectroscopic method.
出处
《实验技术与管理》
CAS
北大核心
2013年第12期58-61,共4页
Experimental Technology and Management
基金
国家自然科学基金(20903028)
关键词
酸碱指示剂
酸离解常数
可见吸收光谱
高斯多峰拟合
acid-base indicator
acid dissociation constants
visible electronic absorption spectroscopy
multi-peaks Gaussian fitting
