作　　者： ; ; ;

机构地区： 广州大学化学化工学院

出　　处： 《实验室研究与探索》 2012年第1期4-8,共5页

摘　　要： 中性红水溶液电离平衡体系的紫外可见吸收光谱特征是酸式HNR+最大吸收峰542 nm与碱式NR最大吸收峰457～470 nm叠合在一起。当pH值升高时,碱式吸收峰强度逐渐增大,酸式吸收峰强度逐渐减小。首次将高斯多峰拟合技术用于中性红水溶液电离平衡体系紫外可见吸收光谱分析,实现了酸式和碱式叠合峰的分峰拟合计算,得到两个吸收峰的积分面积,即峰强度S1和S2。S1和S2之比与NR-和HNR+浓度之比成正比,进而计算中性红水溶液酸离解常数pKa。26.4℃时,用本方法测量的pKa值为7.20,拟合优度精度高,R2、Chi2分别达到0.999和10-5～10-6。拟合计算结果还表明:随着体系pH值增加,中性红碱式吸收峰发生显著蓝移。这种波长位移引起由固定波长建立起来的浓度与吸光度的线性关系发生偏离,引起约3%系统误差。高斯多峰拟合技术改进的pKa分光光度测量方法可广泛用于此类多组分体系紫外可见吸收光谱研究。 UV-visible electronic absorption spectra of neutral red aqueous solutions within a certain range ot pH values were recorded and characterized by the overlap of the principal peak with λmax at 542 and a shoulder with λ max at 457 470 nm assigned to acidic （ HNR^＋） and basic （NR） species of neutral red respectively. The absorbance of HNR^＋ decreased on the contrary, one of the NR increased, with the increase of pH value. A multi-peaks Gaussian fitting technique was first used to interpret the spectra and gave relative integrated absorbance S1/S2 of the two peaks which was considered to be proportional to concentration ration of the HNR^＋ and NR of neutral red and used to calculate the acidic dissociation constants（pKa）. The pKa is 7.20 at 26.4 ℃. The R2 and Chi2 values of the multi-peaks Gaussian fitting reached 0. 999 and 10^-5 - 10^-6 respectively. The blue shift of λmax from 470 to 457 nm for NR was also observed. The standard curves of absorbance of NR maximum absorption wavelength at 457 nm and HNR^＋ maximum absorption wavelength at 542 nm versus concentration of NR^- and HNR^＋ at the neutral red color range would be inaccurate and cause about ＋ 3% systematic error. The spectrophotometric method developed in this paper can be widely used to study UV-visible electronic absorption spectra of similar multi-component systems.

关 键 词： 中性红 分光光度法 酸离解常数 高斯多峰拟合

领　　域： [理学] [理学] [理学] [理学]