激光诱导荧光毛细管电泳DNA检测系统信噪比分析

建立了用于DNA分析的激光诱导荧光检测毛细管电泳系统,分析了垂直入射激发光在毛细管中的行进和高分子溶液电泳筛分介质的瑞利散射及毛细管壁折反射引起的激发光背景噪音.利用光线追迹法计算了折反射引起的背景噪音随激发光和收集方向角度不同时的分布曲线以及荧光在各个方向的分布曲线.两种噪音比较表明,散射噪音比激发光背景噪音低4个数量级,可以忽略.模拟表明,光轴方向荧光最强,90°方向最弱,变化在6.5％内.激发和收集方向成105°时,背景噪音最小,可以获得最大的信噪比,最后对模拟结果进行了实验验证.

Signal to Noise Ratio Analysis for DNA Detecting System by Capillary Electrophoresis and Laser-induced Fluorescence

A laser-induced fluorescence detection system for DNA capillary electrophoresis was set up.Propagation of exciting laser with normal incident angle was analyzed inside the capillary theoretically.Stray light of Rayleigh scattering by the electrophoresis sieving medium and that of refracting & reflecting by capillary tube walls were investigated.Background noise produced by refracting & reflecting was calculated by ray tracing arithmetic when collecting fluorescence at different deflecting angle from incident laser.The distribution curve was plotted.Fluorescence light intensity vs.the deflecting angle was investigated,too.Contributions to the influence on noise of the detecting system by Rayleigh scattering and by refracting & reflecting were compared.The result shows that the former is weaker for 4 orders,and could be omitted.Simulating experiment showed a uniform distribution of fluorescence.Minimum background noise was found at 105°,which gave the largest signal to noise ratio.The calculated result was validated by experiments.