广范pH试纸的荧光pH传感特性及应用

Fluorescence pH Sensing Characteristics and Applications of Universal pH-indicator Paper

对广范pH试纸在pH值2.2~12.5范围内的荧光特性及基于试纸荧光的pH传感系统进行了探索。检测了不同pH缓冲液中浸渍过并晾干的pH试纸的光致发光,并分析了试纸荧光光谱的谱峰频移以及谱带重心频移。实验结果表明,pH试纸的荧光在实验pH区间的变化有明确的规律性,其中在弱酸碱性的pH值(4.0~9.0)范围内,谱带重心λ_B随pH值近似线性变化,相应的经验传感方程为λ_B=603.8-4.09pH。以pH为7对应的荧光谱带重心作参考,其相对灵敏度为0.71%/pH,实验系统的pH分辨力约为0.4。用该实验系统实际测试了稀的尿素水溶液及自来水的pH值,与商用电化学式pH计的结果一致,验证了实验方法及传感系统的通用性、实用性。该实验为pH检测提供了一种较比色读数更加精确客观、成本低廉、数据可靠、样品可保存可追溯的传感方法及测试系统。该系统还可以弥补广范pH试纸不能准确测试弱酸弱碱的不足。

The fluorescence pH sensing characteristics and applications of universal pH-indicator paper in the pH range of 2.2-12.5 were researched.In the experiment,pH-indicator paper strips were dipped into different pH buffer solutions first,then aired dry to be tested under light excitation.The fluorescence spectra were analyzed using peak shift and band barycenter shift.Experimental results indicate that the fluorescence of pH-indicator paper depends on the pH value of tested solution,and the dependence is repeatable.In the pH range of 4.0-9.0,the barycenter wavelength of the emission band is linearly dependent on pH value.As a consequence,pH sensing function ofλB=603.8-4.09pH is obtained.When a pH value of 7 is set as a reference,the relative sensitivity is determined as 0.71%/pH.Resolution of the experimental setup is determined as 0.4.The applications on urea solution and tap-water verify the merit of the sensing method and the corresponding system.The research can offer an optoelectronic method and corresponding experimental system for remote pH sensing.Moreover,the fluorescence pH test is more precise than the strip color judgment with naked eyes,particularly for acidulous or alkalescent solutions.