光谱滴定法在孔雀绿草酸盐指示剂pH值变色域判断中的应用

Application of spectral titration in judging pH discoloration ranges of malachite green oxalate indicator

目的 采用光谱滴定法判断孔雀绿草酸盐指示剂的pH值变色域、滴定终点等指标。方法 利用光谱滴定仪连续测定孔雀绿草酸盐在不同pH值介质中的色变参数、波长与吸光度值等指标,将各指标参数值及其衍生的参数值图形化,通过对各曲线图的分析和筛选,综合评价孔雀绿草酸盐结构变化特征,以确定其变色范围和酸碱滴定终点。结果 孔雀绿草酸盐在pH值0.1~2.0、pH值4.0~7.0、pH值11.0~12.0有化学结构变化,呈现色变,滴定终点为pH值2.0和pH值12.0。结论 光谱滴定法可清晰辨别孔雀绿草酸盐指示剂的pH值变色域和滴定终点,其pH值变色域及色变颜色与文献记载均有所不同。光谱滴定法是分析测定指示剂变色范围、滴定终点、吸收最大波长等的技术手段,为测定数据的准确提供了客观的评价手段。

Objective This paper aims to determine the pH discoloration ranges and titration end point of malachite green oxalate indicator by spectral titration. Methods Through continuous-measurement of the color change parameters, wavelength and absorbance values of malachite green oxalate in different pH media by spectral titrator, graphically analyzing the parameter values of each index and its derived parameter values, screening and analyzing color change curves, and evaluating the structural changes of malachite green oxalate, the color change range and acid-base titration end point was determined. Results Malachite green oxalate had chemical structure changes and color changes at pH 0.1-pH 2.0, pH 4.0-pH 7.0, pH 11.0-pH 12.0. The titration end points were pH 2.0 and pH 12.0. Conclusion The spectral titration method can clearly identify the pH color change range and titration end point of malachite green oxalate indicator, and its pH color change range and the changed color are different from those recorded in the literature. Spectral titration is a technical means to analyze and determine the discoloration range, titration end point and absorption maximum wavelength of indicators, which provides an objective evaluation method for the accuracy of the measurement data.