一种基于中值滤波和统计学的拉曼光谱spike剔除算法

拉曼光谱是一种已广泛应用于化学、生物学和物理学的技术。然而拉曼光谱仪的电荷耦合器件很容易受到宇宙射线的影响,从而产生随机的窄带宽、高强度的spike。在真实样品中出现概率较低,约为千分之一,但一旦出现将严重降低信号对比度。该研究提出一种实用的spike剔除算法。该算法对中值滤波后的数据与原始数据作差,得到偏差数据。用分位数的方法将偏差数据从小到大排序,取中间99%数据作为真实数据作高斯分布拟合。根据spike强度高,稀疏的特性,以光谱中高强度数据的出现概率作为阈值标准剔除spike。最后以中值滤波结果带入原始数据代替spike,从而最大程度还原样本原始信息且不需任何调试参数。以加入不同强度spike的拉曼光谱作为验证对象,实验结果表明本算法对spike检测与去除的灵敏度可以高达99.5%。本算法同时适用于一维拉曼光谱、二维拉曼图像和三维拉曼数据立方体,且算法表现随着维度的增加而提高,一维spike剔除算法能检测超过最大峰强度40%的spike,而在三维拉曼数据立方体中,超过峰值20%的spike即能被检测出。用该算法对40 000条真实拉曼光谱进行处理,可以在不扭曲真实信号的情况下有效...     

一种基于拉曼光谱的石油产品快速分类方法

提出了一种基于拉曼光谱的石油产品快速分类方法.首先,利用经过谱图预处理的石油产品训练样本拉曼谱图构建模型知识库,计算各类别的特征拉曼谱图和类内阈值;其次,将石油产品测试样本的拉曼谱图经过相同的预处理,再计算其与各类别特征拉曼谱图的线性相关系数,若最大相关系数大于或等于最大相关系数对应类别的类内阈值,则该样本属于此类别....     

一种与光镊结合的显微拉曼光谱技术

论述了一种与光镊结合的显微拉曼光谱即光镊-显微拉曼光谱系统的构建方案。给出了利用该系统测得的活细胞(大白鼠血细胞,酵母细胞)的微区拉曼光谱,并将红外光镊束缚下的Ar+激光激发的血细胞的拉曼光谱,与用单一Ar+激光光镊束缚并同时激发的血细胞拉曼光谱,以及血细胞直接贴在基底上的拉曼光谱进行了分析对比。实验表明,前者比后两种实验方案的血细胞拉曼光谱信号有显著提高。分析了红外1064 nm光镊激光和可见514.5 nm Ar+激光对活细胞的损伤效应,发现高功率的红外激光对细胞的损伤作用远小于低功率的Ar+激光。并将该系统应用于碳纳米管材料分析,获得了单壁碳纳米管的拉曼光谱。     

一种提高生物体拉曼光谱痕量测量精度的方法

微量物质拉曼光谱测量精度的提高是拉曼分析技术的难点之一,特别是高荧光背景下生物体中微量物质的测量。根据拉曼谱峰突发、离散特点,分别给出荧光背景和噪声拟合函数,通过监测总体拟合偏差A类不确定度函数实现拉曼谱峰定位和干扰信号滤波;进一步根据谱峰位置划分光谱区间,在单调区间内弱化非谱峰信号,实现谱峰信号增强。与其他光谱处理方法比较,可以准确拆分重叠特征峰,不会降低特征峰高度,提供更加灵敏的半谱峰面积指标。实验表明,该方法在处理皮肤拉曼光谱时,可以准确得到螺旋构象的酰胺I带、神经酰胺和CO的归属拉曼谱峰;另外经过该方法处理后数据建立水溶性糖(水稻叶片)含量测量模型,其精度优于小波分解、多项式拟合和非线性最小二乘法。     

一种危险液体混合物的拉曼光谱定性定量识别方法

危险液体混合物的拉曼光谱定性定量分析一直是现场应用难点,为解决该问题,分析了多种物质混合后拉曼光谱的峰位、峰值、峰型变化情况,选取拉曼光谱关键特征峰进行数学简化,构建了从混合物物质成分到混合物拉曼光谱的映射关系,该映射关系描述多种物质成分混合的混合物拉曼特征峰响应只和混合物中各成分本身拉曼特征峰响应以及各物质成分混合比例有关,各物质成分按混合比例贡献拉曼特征谱峰,共同形成最终的混合物拉曼光谱。由该映射关系求逆,可实现从采集到的混合物拉曼光谱计算出各物质成分的混合比例。基于此,设计了危险液体混合物成分定性定量识别方法,主要方法步骤包括,首先进行拉曼光谱数据采集,然后进行拉曼光谱数据处理并获得拉曼特征峰,再进行测试样品与数据谱库标准品的正反向特征峰匹配,如果正反向特征峰匹配系数都比较高,在满足一定阈值条件下,可认定测试样品是某种纯净物,如果不是纯净物,则进入混合物分析,通过拉曼光谱特征峰反向匹配系数筛选,确定混合物成分构成,混合物成分确定后再进行混合物成分比例计算,最终实现危险液体混合物定性定量分析。实验部分,选定丙酮、甲苯、三氯甲烷、乙醇及其混合物进行实验验证,当混合物样品是丙酮、乙醇两种成分按3∶7比例混合时,经拉曼光谱识别方法计算,混合成分计算值是丙酮占比0.245 7,乙醇占比0.706 0;当混合物样品是甲苯、三氯甲烷两种成分按3∶7比例混合时,经拉曼光谱识别方法计算,混合成分计算值是甲苯占比0.323 4,三氯甲烷占比0.763 0;当混合物样品是丙酮、甲苯、乙醇三种成分按4∶3∶3比例混合时,经拉曼光谱识别方法计算,混合成分计算值是丙酮占比0.795 9、甲苯占比0.303 5、乙醇占比0.287 5,实验结果表明,当危险液体混合物成分是两种或三种成分混合时,混合成分计算值基本和实际值吻合,应用危险液体混合物的拉曼光谱定性定量识别方法,可较准确的从拉曼混合光谱中解析出各混合物成分以及各成分在混合物中的比例,可以判断混合物每个拉曼特征谱峰都来自于哪个成分或哪些成分拉曼特征谱峰的混合,谱图解析结果良好,对危险液体混合物现场分析鉴别有较大应用价值。     

拉曼光谱在线测量技术在聚合物合成与加工中的应用研究进展

聚合物的合成与加工过程影响着材料的聚合度、结晶度、取向度以及共混组分的均匀性,最终影响聚合物产品的性能。因此对聚合物合成与加工过程中材料的实时状态进行监控至关重要。拉曼光谱在线测量技术凭借其无损检测、采样简单、可靠性高,对试样的外形和物态没有任何特定要求,且能在高温、高压、有毒的环境中直接进行在线测量等特点,在高分子材料合成与加工领域有了越来越广泛的应用。将此在线测量技术应用到高分子合成与加工过程中,实时测量高分子材料的化学组成和物理性质,并将测量数据用于控制合成与加工过程,可以提高高分子材料的性能。本文选择聚合反应转化率、聚合产物粒径及其分布、聚合物结晶度、聚合物取向度、多相共混聚合物组分含量等五个反映聚合物合成或加工过程状态的参量,概述了拉曼光谱在线测量上述参量的相关研究进展,并对拉曼光谱在线测量技术在聚合物合成及加工中的应用发展进行了展望。     

核酸碱基和核苷的高效液相色谱——表面增强拉曼光谱在线联机分析研究

本文将反相高效液相色谱(RP——HPLC)与表面增强拉曼光谱(SERS)联机,对三个核嘧啶、四个核嘌呤和两个核嘧啶及其核苷混合物进行在线联机分析研究。在流动条件下,对影响 SERS 测定的因素,如激光照射、温度、pH 值、流速、记忆效应,以及联机系统的接口装置等进行了讨论。文中给出了联机测得的三维和二维 SERS 色谱图。     

酿造酒的激光拉曼光谱

用激光拉曼光谱的方法对市场销售的几种酿造酒进行了研究，对酿造酒的拉曼光谱的归属进行了设定，并指出了拉曼光谱对鉴别酒的质量所具有的意义     

Monitoring deprotonation of gallic acid by Raman spectroscopy

Gallic acid (GA) is involved in many biochemical processes and reactions and is of great importance in environment thanks to its antioxidant and pro‐oxidant properties. We present in this paper a comprehensive study of GA deprotonation by means of Raman spectroscopy. In the Raman spectra, we identified the characteristic bands that were sensitive to the five pH‐dependent GA forms. From these results, we extracted the GA pKa values that are consistent with the reference values. These results permit the monitoring of GA forms for applications. Copyright © 2015 John Wiley & Sons, Ltd.     

基于双尺度相关运算的拉曼谱峰识别方法

拉曼谱峰识别是拉曼定性分析中的关键技术之一, 针对现有拉曼谱峰识别方法中存在的缺陷和不足提出了一种双尺度相关拉曼光谱谱峰识别方法,即采用两个尺度下的相关系数与局部信噪比相结合来实现拉曼谱峰识别。利用MATLAB对所提算法与传统的连续小波变换法进行了对比分析,并通过实测拉曼光谱进行验证。分析结果：双尺度相关法识别一幅拉曼谱的平均时间为0.51 s,连续小波变换法为0.71 s;当谱峰信噪比≥6时(现代拉曼光谱仪器均可达到较高的信噪比),双尺度相关法的谱峰识别准确率高于99%,连续小波变换法的谱峰识别准确率小于84%,且双尺度相关法谱峰位置识别误差的均值与标准差均要小于连续小波变换法。通过仿真对比分析和实验验证表明：双尺度相关法具有无需人工干预,无需做去噪及去背景等预处理操作,识别速度快,识别准确率高等特点,是一种切实可行的拉曼谱峰识别方法。     

A Laser Source with High Spectral Purity for Simple Tunable Laser Raman Instrument

The authors present an external cavity diode laser with high spectral purity for tunable laser Raman spectroscopy. To achieve high spectral purity required for Raman spectroscopy, a laser cavity utilizing a volume phase holographic grating, which has very low stray light, is developed and the first-order diffracted beam from the grating is taken as the output. Raman signals can be obtained from common samples with only a commercial laser rejection filter, greatly simplifying a tunable Raman instrument.     

Information‐theoretic chemometric analyses of Raman data for chemical reaction studies

A methodology of multivariate chemometric techniques based on the information‐theoretic approach was applied for elucidating chemical reaction information from a Raman data array R _m×ν that arises from in situ reaction monitoring. This reaction‐induced dynamic dataset R _m×ν can be contaminated by random cosmic ray spikes found in the midst of characteristic spectral variations associated with the disappearance or emergence of Raman active reactants, intermediates and products. Such spurious cosmic spikes were identified and removed using a novel and fast numerical approach based on maximum and minimum spectral entropy principles while preserving the genuine reaction‐induced spectral variations. Subsequently, the band‐target entropy minimization (BTEM) algorithm, a minimum spectral entropy based self‐modeling curve resolution technique, was applied to recover the pure component spectra of Raman active chemical species. Information gain through the chemometric analyses was calculated using information entropies with base 2 logarithm. This sequence of information‐theoretic chemometric analyses (or transinformations) was successfully tested on the reaction spectral data obtained from alcoholysis of acetic anhydride, which contains four Raman active chemical species. It is envisioned that this series of multivariate statistical analyses will be useful in chemical reaction studies and process analytical technology (PAT) applications that utilize in situ Raman spectroscopy to monitor transient dynamic changes in chemical concentrations, and also in Raman microscopy/imaging data containing spatial variations. Copyright © 2010 John Wiley & Sons, Ltd.     

Simple and inexpensive instrument for deep‐UV Raman spectroscopy

Deep‐UV Raman spectroscopy is a powerful way to collect chemically specific information about complex samples. The availability of inexpensive and reliable light sources in the spectral region below 250 nm has been always considered a major bottleneck problem on the way of a widespread of this powerful spectroscopic technique. We report on the efficient fourth‐harmonic generation of a low‐power microchip Nd:YAG laser operating at 946 nm. High‐quality deep‐UV Raman spectra were collected using a newly developed laser source. Copyright © 2013 John Wiley & Sons, Ltd.     

Monitoring the liquid phase concentration by Raman spectroscopy in a polymorphic system

In this work, Raman spectroscopy was successfully used for the quantitative determination of the liquid phase concentration in an aqueous polymorphic system of D‐mannitol. An extensive study has initially been performed to identify the influence of the solid state, e.g. particle size, particle amount, and different polymorphs, on the intensity of the characteristic Raman solute signal. It was found that the existence of solid phase can decrease Raman intensity, and this influence is more significant when the suspension density is higher, e.g. with smaller size and larger amount of particles. Based on this information, a large number of samples were examined by Raman spectroscopy in the form of clear solutions and suspensions. The spectral preprocessing and partial least squares (PLS) regression were then used to relate the solute concentrations to these spectral data, independent of solid state. Several PLS calibration models were developed with different treatments to the spectral data, and the optimized strategy was finally demonstrated. Particularly, a reference peak at 578 cm⁻¹ related to the sapphire in the Raman probe window was innovatively applied to reduce the influences from the equipment and other external variations, with which the full‐spectrum PLS model was seen to give more stable results rather than partial spectral regions. The optimized model was subsequently applied to predict the liquid phase concentration in a multiphase multicomponent dynamic process, the solvent mediated polymorphic transformation (SMPT) of mannitol, and it was shown that the offline measurements and the predicted values were mainly in agreement with one another. Copyright © 2015 John Wiley & Sons, Ltd.     

一种用多色光作为激发源产生拉曼光谱的新算法

探讨用多色光代替激光作为拉曼光源的新型拉曼光谱仪的可能性。根据拉曼光谱原理, 并通过数学分析, 发现当用多色光照射在样品上时, 所得到的散射光经散射频率校正后在不同频率上的强度分布可以写成样品的Raman-Rayleigh联合散射谱和激发光光源的功率谱的卷积。利用傅里叶变换算法,有可能从多色光照射样品所得到的散射光谱中导出样品的拉曼光谱。基于上述原理,可能发展出不用激光的新一代拉曼光谱仪。     

Raman Spectroscopy for Protein Analysis

Abstract

Proteins are essential parts of organisms and participate in virtually every process within cells. Raman spectroscopy can be a powerful tool for the characterization of modified amino acids and proteins. In addition to the potential for quantitative results, it offers the advantage of not requiring any sample preparation. This review focuses on applications for protein analysis, published in the period 2010–2014.     

遗传算法用于多组分拉曼光谱定量分析的研究

拉曼光谱是一种分子散射光谱,利用物质的特征拉曼光谱,可实现对其结构、成分、浓度等的检测.多组分物质拉曼光谱的定量分析是一个有待深入研究的课题.采用遗传算法程序对10组分的混合矿石样品的拟合拉曼光谱数据进行了分析,对同一条件下算法多次计算的结果和不同条件下算法的表现进行了讨论,分析了算法设计和基本参数的不同对算法收敛速度以及对计算结果的精确性和稳定性的影响,验证了遗传算法用于多组分样品拉曼光谱数据分析的可行性、有效性和精确性.