【作者】 杨涛；

【导师】 李崇瑛；

【作者基本信息】 成都理工大学 ， 应用化学， 2008， 硕士

【摘要】 色谱是当今分析化学发展较快、应用较广的分离分析技术。如果色谱信号含有噪声,就会造成对色谱峰的起点、终点、保留时间、峰高不能准确判断识别,峰面难以准确计算,从而影响了色谱的定量定性分析。因此,研究色谱信号滤噪对提高检测限、分析结果的精密度和准确度具有十分重要的意义。本文介绍了小波变换、小波滤噪原理以及小波变换在MATLAB的实现技术:在结合色谱信号的特点的基础上,提出了色谱滤噪的性能评价指标(峰面积、峰高、保留时间相对误差及信噪比),建立了基于小波变换的色谱数据滤噪方法。在方法的建立过程中,根据评价指标,用模拟仿真的色谱图对八种小波、七层分解层数、四种阈值算法及两种阈值函数进行了选择。通过大量的实验数据对比以及根据评价指标,最终选择了db4小波,分解层数为5或6,阈值算法heursure规则,阈值函数软阈值的组合进行色谱滤噪。用模拟仿真色谱图进行方法验证结果表明,该方法能提高信噪比,滤噪后色谱图失真较小,在低信噪比的情况下,峰面积、峰高、保留时间的相对误差分别小于5%、5%、1%。用实际的辣椒红色素、大黄、五味子等多种色谱图滤噪结果表明,该方法能在保留信号的特征信息时有效的滤除信号中的噪声,并且峰起点终点位置十分清晰,有利于定量定性分析。总的来说,该方法简便快速,对被处理信号无任何限制,而且仅需一次滤波即可达到处理要求,节省处理时间。更多还原

【Abstract】 Chromatography is a much faster and more extensive analysis separation technique in analytical chemistry, nowdays. If there is noise in chromatographic signal, it will be difficult to distinguish exactly peak jumping-off point, peak end-point, retention time and peak height , calculate peak area and finally have influence on the quantitative and qualitative analysis in chromatography. So it is very significative to improve the detection limit and the.accuracy and precision of analytical result.The paper introduces wavelet transform, the de-noise theory based on wavelet and its realization in MATLAB software. Then on the basis of traits of chromatographic signals, the evaluating standards, such as peak area relative deviation, peak height relative deviation, retention time relative deviation and signal to noise ration are put forward and the method of de-noising of chromatographic signal based wavelet transform is established.In the process of method establishment, eight waves, seven decomposed levels, four threshold estimators and two threshold functions were chosen by simulated chromatogram, according to evaluated standard. Through a large number of experimental data comparison, the noise filtering method which consists of wavelet db4, decomposition level to 5 or 6, the threshold algorithm heursure and the threshold function soft threshold value is chose to filter noise. Tested by using simulated chromatogram, the results show that the method has a serial of virtues, such as improving the signal to noise ratio, having smaller distortion after filtering noise, and even when the signal has high noise the relative deviation of the peak area ,peak height and retention time are less than 5%, 5% and 1% respectively.Meanwhile, the results of a lot of tests using actual chromatography data, such as capsanthin, rhubarb, Schisandra, and some other chromatographys to filter noise prove that the noise in the original singal could be cleanly eliminated, the characteristics of the signal could be preserved completely ,the position and height of peaks is very clear and it is useful to do quantitative qualitative analysis.In summary, the method is very simple and rapid, which has no restriction on after signals processed, but needs only one filtering to meet processing requirements, and it shortens the processing time.更多还原