基于净信号的乙醇含量拉曼光谱分析方法研究

拉曼光谱检测技术由于其快速、无损等优点可以满足工业现场测量的要求,因此已经广泛地应用于各种定量定性的分析领域。酒精度即乙醇含量的体积比是酒类产品品质检测中的关键参数,开发乙醇含量实时、便捷的检测系统对酒类产品生产具有重要的意义。将净信号分析方法应用于乙醇水溶液拉曼光谱的定量分析中,将乙醇的净信号与其浓度建立一元线性回归模型。结果表明,基于净信号回归的乙醇拉曼光谱定量分析方法,相比较于特征峰强一元线性回归模型和偏最小二乘回归模型,不仅提高了模型的预测精度,增强了模型的稳健性,便于模型传递,而且模型算法简洁、稳定,便于实现便携式仪器的开发。     

拉曼光谱定量分析乙醇含量的非线性回归方法研究

传统拉曼特征峰峰比法一般采用线性回归法建立乙醇浓度与峰峰比的线性关系从而反演乙醇浓度实现乙醇定量分析,但仅在较低浓度范围适用。针对这一问题,采用自主研制的激光拉曼乙醇含量检测系统实验研究了不同浓度乙醇溶液拉曼光谱特征峰(非对称CH₂伸缩振动2 924.0 cm-1)与本底水峰(3 350 cm-1)相对强度关系,提出适用于大范围乙醇浓度测量的非线性回归分析方法。利用邻域平均算法去除拉曼光谱突变噪声,结合多点插值处理实现光谱基线校准。基线校准及归一化处理后,可有效消除突变噪声及强荧光背景的影响。分别采用二次多项式和e指数数学模型对拉曼峰值强度比随乙醇浓度变化关系进行非线性回归并与线性回归分析进行对比。结果表明,线性拟合相关系数约为0.991,线性回归模型乙醇浓度准确测量的适用范围为15%～60%;非线性拟合相关系数高于0.997,非线性回归模型乙醇浓度精确测量的适用范围为3%～97%。非线性数学模型可为乙醇溶液浓度定量分析提供理论基础,将该数学模型应用于乙醇含量检测系统,可实时反演较为精确的乙醇浓度,从而实现大浓度范围内具有荧光背景干扰的乙醇溶液快速、实时、准确的定量分析。     

Teaching Raman Spectroscopy in Both the Undergraduate Classroom and the Laboratory with a Portable Raman Instrument

We have evaluated a small portable Raman instrument on loan from B&W Tek, Inc., and have determined that it can successfully be used in the classroom both as a visual aid for teaching the fundamentals of Raman spectroscopy and for a variety of undergraduate experiments as a normal component of an instrumental analysis class. Having portable Raman instrumentation would allow the instructor to demonstrate the principles of Raman spectroscopy, as well as the concepts of calibration curves, blank subtraction, detection limits, and regression analysis. Both qualitative and quantitative types of experiments were done for solid Tylenol tablets, aqueous solutions of isopropyl alcohol, dimethyl sulfoxide, methanol, and ethanol, and gaseous CO₂ and N₂O₄. Additionally, surface‐enhanced resonance Raman spectra of Rhodamine 6G were obtained using a chloride ion–activated silver colloid. Spectra from the B&W Tek, Inc., instrument were comparable to literature Raman spectra.     

多波长消荧光拉曼光谱仪的研制及应用研究

拉曼光谱技术作为探究分子、晶体及其结构特征的有力手段,具有快速、无损、样品用量小、无需前处理且适应性强等优点,已被广泛应用于食品安全、石油化工等领域。但在拉曼光谱应用中,常常受到荧光背景干扰,导致拉曼信号降低,严重的情况下拉曼信号甚至会淹没在荧光背景中。为解决拉曼技术在实际应用中荧光背景干扰的问题,从仪器角度出发,采用二色镜对多波长拉曼光谱进行光路耦合设计,研制了近红外拉曼光谱与移频差分拉曼复合一体的多波长消荧光拉曼光谱检测系统,其中近红外拉曼光谱采用1 064 nm激光光源设计,移频差分拉曼光谱选取784.5和785.5 nm两组激光光源进行时分复用,在移频差分拉曼光谱检测的同时,亦可获得两组单波长拉曼光谱数据。通过对比同步测试和分时逐次测试的强度及峰位稳定性,验证了多波长消荧光拉曼光谱仪的同步测试性能;选取了多种荧光背景强弱不同的样品,进行了单波长拉曼、近红外拉曼及移频差分拉曼光谱的对比分析。针对丙酮、乙腈等荧光背景较弱的样品,可采用单波长拉曼光谱对样品进行定量及定性分析;针对食用油、红色塑胶微粒等荧光背景与拉曼信号强度相当的样品,可采用近红外拉曼光谱对样品进行定量及定性分析;针对红酒、棕色塑胶微粒等荧光背景较强的样品,需结合近红外拉曼光谱和差分拉曼光谱对样品进行定性分析。研究表明：通过多波长消荧光拉曼光谱检测系统的研制,在常规单波长拉曼光谱技术的基础上,将两种抑制荧光干扰技术有机结合,有效扩充了应用领域及样品检测范围。     

一种基于石墨化炭黑过滤吸附处理荧光抑制和改进系统聚类分析的轻质燃油种类拉曼光谱快速识别方法

提出了一种石墨化炭黑过滤吸附前处理抑制轻质燃油拉曼光谱荧光背景干扰的方法和一种改进的系统聚类分析算法,实现了39个样品的种类快速识别,即能自动将样品识别为0#车用柴油、0#普通柴油、97#车用汽油、93#车用汽油、90#车用汽油和3#喷气燃料等6种类型。过滤吸附处理方法是用定制的50 mg石墨化炭黑过滤吸附0.75 mL油样,然后对其进行拉曼光谱数据采集。试验结果证明：石墨化炭黑过滤吸附处理对无荧光背景干扰的3#喷气燃料和车用汽油样品拉曼光谱特征无明显影响,且能够有效抑制车用汽油和车用柴油样品的拉曼弱荧光背景干扰,以及车用汽油和普通柴油的强荧光背景干扰。改进的有监督系统聚类分析算法将普鲁克距离作为系统聚类分析中样本间相似度的评价方法;并将经典的系统聚类分析视为标准校正样品集的“建模”过程,通过计算未知样品与各类属中心向量之间的普鲁克距离,依据距离最小原则判断未知样品的类属。通过对39个具有不同拉曼荧光背景干扰特征油样的石墨化炭黑前处理和“留一法”交互验证分类识别,分析结果证明：石墨化炭黑过滤吸附前处理抑制拉曼光谱荧光背景的方法能够有效提取轻质燃油的拉曼光谱特征并应用于定性种类识别。     

Using Raman Spectroscopy for Determination Methanol Quantity in Illegal Alcoholic Beverages

Illegal production of alcoholic beverages is a common problem in most countries.The consumption of these counterfeit alcoholic products in Turkey has increasingly been one of the major health concerns.In this study,a comparison between GC-MS and Raman spectroscopy techniques was made to determine the amount of methanol in BogmaRaki which is a counterfeit alcoholic beverage produced and consumed in Hatay region. Different ratios of methanol/ethanol concentrations were prepared to obtain a calibration curve.This curve was used to measure the amount of methanol in the actual product samples using both GC-MS and Raman spectros-copy techniques.Results obtained from both techniques were compared using Paired sample t-tests.The Limit of Detection and the Limit of Quantification values were determined as 0.03 (%v/v)and 0.11 (%v/v),re-spectively.Both techniques demonstrated a similar sensitivity in the determination of methanol concentration in these counterfeit products (p>0.05).Raman Spectroscopy,however,has an advantage of being easy to use, inexpensive,rapid and non-destructive analytical technique with little or no sample preparation.     

A novel method for quantification of ethanol and methanol in distilled alcoholic beverages using Raman spectroscopy

In this study, direct quantification of ethanol and methanol in distilled alcoholic beverages using Raman spectroscopy was performed. Raman spectra of varying ethanol–methanol mixtures were obtained, baseline corrections were made, and the data were normalized using Raman scattering intensity of an internal standard (acetonitrile, 921 cm^–1). Then, calibration graphs were produced for ethanol and methanol concentrations in the ranges of 0–7 M and 0–10 M, respectively. Accurate R² values of the calibration graphs proved the notable linear correlations (0.998 for ethanol and 0.998 for methanol). The method was validated based on linearity, sensitivity, intraday and interday repeatability, and recovery tests. The limit of detection and limit of quantification values of the validated method were determined for ethanol concentration as 1.2 and 3.7 mM, and for methanol concentration as 3.4 and 10.3 mM, respectively. The ability of the developed method to detect ethanol and methanol concentrations in real samples was also investigated. The results of the developed method were compared with the experimental results from traditional method and high correlation value (R² = 0.926) was obtained. Besides being sensitive and cheap, the developed method is rapid with the analysis time of less than 30 s. Furthermore, it eliminates labor‐consuming operations, chromatographic separation, and measurement error due to the high number of experiment steps in the standard method. Copyright © 2012 John Wiley & Sons, Ltd.     

便携式拉曼光谱仪用于合成大麻素类物质快速定性分析探究

我国于2021年7月将合成大麻素类物质整类列入管制,在一线查缉现场对疑似合成大麻素样品进行快速定性分析是办案民警的迫切需求。研究系统考察了拉曼光谱对合成大麻素的整体区分能力,比较了四款手持式拉曼光谱仪分析实际缴获样品时的结果差异,探讨了制约拉曼光谱在一线查缉现场广泛应用的原因。ProTT-EZRaman-A7便携式拉曼光谱仪的整体性能介于台式拉曼和手持式拉曼之间,选用该仪器采集了90种合成大麻素对照品的拉曼光谱,并利用兼容性强的KnowItAll软件建立了90种合成大麻素通用拉曼光谱库。分析90种合成大麻素的拉曼光谱,结果表明,当不存在荧光干扰时,拉曼光谱可以区分所有合成大麻素物质,但对部分结构相差一个甲基、卤素原子等的结构类似物区分度欠佳。不同款拉曼光谱仪的性能差异大,为考察其原因,本研究选用了四款手持式拉曼光谱仪分别对120份实际缴获合成大麻素样品进行了测定,随后使用KnowItAll软件并选用包含90种合成大麻素的通用拉曼光谱库对每张光谱图进行谱库检索。四款手持式拉曼光谱仪的正确匹配率分别为71.7%, 68.3%, 46.7%和24.2%。抗荧光干扰能力和分辨率的不同是造成不同...     

拉曼光谱定性和定量检测青蒿素研究

青蒿素是从中药青蒿中提取的含有过氧基团的倍半萜内酯药物,具有良好的抗疟特性,是治疗疟疾的特效药。运用激光拉曼光谱分析了100～3 500 cm-1光谱范围内青蒿素的声子振动特性。指出位于724 cm-1的拉曼峰为与青蒿素中过氧基团直接相关的一个特性声子振动模式,可用于检测过氧桥键的存在。位于1 734 cm-1的拉曼峰为与青蒿素中内酯基团直接相关的一个特性声子振动模式,可用于进一步检测分析青蒿素。由于这两个特征拉曼峰对应于青蒿素分子中特征化学键的振动,而且在实验上较容易观察分析,因而它们可以很好的用于拉曼光谱法快速初步定性检测青蒿素。同时,通过分析比较不同纯度青蒿素样品中724和1 734 cm-1处特征拉曼峰的平均散射信号强度比,拉曼光谱法可以用于定量检测青蒿素样品的纯度。与常用的高效液相色谱法相比,拉曼光谱法更快速方便,检测精度更高,而且可以检测青蒿素样品纯度的均匀性。拉曼光谱法定性和定量检测青蒿素纯度的功能对分析检测中药青蒿的品质也有重要意义。     

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。     

Applications of Raman Spectroscopy in Agricultural Products and Food Analysis: A Review

Abstract

Raman spectroscopy has been gaining popularity as an analytical tool due to advances in development of Raman spectrometry and the power of personal computers. Due to to its narrow and highly resolved bands, Raman spectroscopy allows for nondestructive extraction of chemical and physical information about samples and aids in rapid on-line analysis without any special sample preparation. In this review, Raman spectroscopic techniques such as dispersive Raman spectroscopy, Fourier transform Raman spectroscopy, surface-enhanced Raman spectroscopy, and spatially offset Raman spectroscopy are briefly introduced. In addition, applications of Raman spectroscopy are explored, within various fields of agricultural products and food, including fruits and vegetables, crops, meat and dairy products, oil, as well as beverages. In addition, some discussion on the importance of Raman spectroscopy as fundamental and applied research of agricultural products and food is provided.     

拉曼光谱技术在农产品质量安全检测中的应用

农产品的质量安全与我们老百姓的身体健康和生命安全密不可分。传统的化学检测方法具有需要样品前处理,操作过程复杂以及破坏样品等诸多缺陷。拉曼光谱技术作为一种分析、测试物质分子结构强有力的表征手段,可以快速实现样品的无损伤、定性定量检测分析。随着拉曼光谱技术的不断完善和应用范围的逐渐拓宽,拉曼光谱技术在农产品的质量安全检测中发挥着极其重要作用,并且具有广阔的应用前景。目前,已经有大量的基于拉曼光谱技术检测农产品质量安全的相关研究报道,为了解拉曼光谱技术的检测原理以及发展现状,并跟踪国内外最新研究进展,简述了拉曼光谱技术的基本原理及其发展、拉曼光谱检测装置,深入综述了拉曼光谱技术在果蔬、禽畜、粮食质量安全检测中的最新研究进展,指出了拉曼光谱技术应用在农产品质量安全检测中的现存的技术问题。另外,还简要介绍了国内外部分拉曼光谱仪的部分信息和便携式拉曼光谱仪专利申请状况,展望了该项技术的研究方向和应用前景。     

Identification of waste cooking oil and vegetable oil via Raman spectroscopy

This paper made a qualitative identification of ordinary vegetable oil and waste cooking oil based on Raman spectroscopy. Raman spectra of 73 samples of four varieties oil were acquired through the portable Raman spectrometer. Then, a partial least squares discriminant analysis (PLS‐DA) model and a discrimination model based on characteristic wave band ratio were established. A classification variable model of olive oil, peanut oil, corn oil and waste cooking oil that was established through the PLS‐DA model could identify waste cooking oil accurately from vegetable oils. The identification model established based on selection of waveband characteristics and intensity ratio of different Raman spectrum characteristic peaks could distinguish vegetable oils from waste cooking oil accurately. Research results demonstrated that both ratio method and PLS‐DA could identify waste cooking oil samples accurately. The identification model based on characteristic waveband ratio is simpler than PLS‐DA model. It is widely applicable to identification of waste cooking oil. Copyright © 2016 John Wiley & Sons, Ltd.     

Application of portable Raman spectroscopy and benchtop spatially offset Raman spectroscopy to interrogate concealed biomaterials

In this paper, we demonstrate the ability of portable Raman spectroscopy and benchtop spatially offset Raman spectroscopy (SORS) techniques to rapidly identify real and fake ivory samples. Both techniques were able to identify exposed genuine from fake ivory samples. In contrast to conventional Raman spectroscopy, SORS was, in addition, able to identify ivory concealed by plastics, paints, varnishes and cloth. Application of the SORS technique allows the interrogation of biomaterial samples through materials in which conventional Raman spectroscopic instrumentation cannot penetrate. Copyright © 2009 John Wiley & Sons, Ltd.     

拉曼光谱中荧光抑制技术的研究新进展综述

拉曼光谱技术反映了物质的结构特征,可用于分析有机或者无机样品的化学组分。但由于某些被测物的荧光背景远远强于拉曼信号,这些物质的拉曼光谱测量有时十分困难,这限制了拉曼光谱的广泛应用。因此有必要在拉曼检测中对荧光采取抑制措施以准确获取高信噪比的拉曼光谱指纹信息。近些年来,很多的相关研究探讨及发展了多种荧光抑制的新方法。在目前的科研活动中,常用的技术有表面增强拉曼光谱技术、傅里叶变换拉曼光谱技术、共焦显微拉曼光谱技术和高温拉曼光谱技术等。这些技术解决了拉曼光谱早期存在的一些问题,如荧光干扰、灵敏度低等,极大地扩展了拉曼光谱技术在各个领域的应用。而这些新方法可大致归类为物理/化学方法,基于光学性质不同衍生的方法,计算处理方法和其他方法。文章概括性的介绍了上述方法的理论、实现方式,并分析比较了各自的特点。     

Simultaneous Raman micro–spectroscopy of optically trapped and stacked cells

The combination of Raman spectroscopy and optical trapping holds great promise for single‐cell studies and is an emergent theme in microfluidic environments. Here, the evolution of the Raman signal intensity with an axial increment of the mass of the substance of interest inside a specific Raman excitation volume is investigated. Whilst Raman spectroscopy may be applied to tissue samples, solutions and single cells, there are no easily available methods to rapidly acquire signals from small cell populations. We show a simple but powerful method to record the Raman intensity signal simultaneously from a small number of trapped cells or colloidal particles using the technique of optical stacking. The Raman spectra of stacks of red blood cells and yeast cells show that this method can be applied to biological systems. We demonstrate how we may reveal biochemical fingerprints that would otherwise require long integration times for each single cell or averaging over many sequentially acquired cell spectra. There is potential to apply this method to directly attain Raman spectra from sorted sub‐populations of normal, abnormal and tumour cell lines. Copyright © 2007 John Wiley & Sons, Ltd.     

拉曼光谱在水质分析中的应用:展望及系统设计

拉曼散射光谱是一种研究物质结构强有力的工具,目前已经逐渐应用于许多领域,但在水质分析方面的应用讨论尚少。本文首先对拉曼光谱应用于水质分析的可行性及优越性进行了分析,并在此基础上设计了一套新型的应用微机和进经神经网络实现的拉曼光谱水质分析系统,以达到对水质进行高效、准确的定性和定量分析的目的。     

气体拉曼传感增强技术研究进展与趋势

不论是在科学研究,食品安全,医学检测,还是在安全事故预防等领域,对多组分混合气体进行快速、准确的定性定量分析已经成为一种迫切的需求。拉曼光谱法是一种强大的气体传感方法,既能克服传统的非光谱法检测时间长、重复性差等弱点,又能弥补吸收光谱法无法直接测量同核双原子分子的缺点,同时还能使用单一频率的激光器对多组分混合气体进行定性和定量分析。但由于物质固有的弱拉曼效应,加之气体的拉曼效应一般远低于固体和液体,这极大地限制了拉曼光谱法在气体传感领域的应用。如何提高气体的散射强度是使气体拉曼传感技术得到更广泛应用的关键。目前最主要的气体拉曼传感增强技术包括腔增强技术和光纤增强技术。腔增强技术从提高与待测气体作用的激发光强度和作用路径来从源头上增强拉曼散射信号,包括多次反射腔增强、 F-P腔增强、激光内腔增强。光纤增强则从提高球面散射光的收集效率来增强拉曼散射信号,使绝大部分拉曼散射光都能进入光谱探测器,包括镀银毛细管增强和空芯光纤增强。简要介绍了上述两种技术的的增强原理,汇总了研究进展以及应用现状,并讨论了它们各自的优势以及局限性,最后着眼于多组分痕量气体的检测,展望了气体拉曼传感技术未来的发展趋势...     

拉曼光谱编码的荧光液相生物芯片检测系统研究

随着医疗诊断需求的增加,生物分子检测技术越来越受到人们的重视,液相生物芯片技术作为一种高通量,多通道的分子检测手段在近几年得到了飞速发展。通过层层自组装方法制备以微片为载体的拉曼光谱编码液相生物芯片,并利用自行搭建的一套高灵敏度、高分辨率的光学系统,实现对液相生物芯片的定性与定量分析。光学系统由拉曼光谱检测系统与荧光显微成像系统耦合而成。在拉曼光谱检测系统中激光器发射出785 nm波长的激光,通过二向色镜,带反反射镜与物镜汇聚到样品上,样品产生的拉曼散射光,经物镜,带反反射镜,二向色镜与拉曼滤波片,最后通过凹透镜聚焦到光谱仪的狭缝上,光谱仪色散实现在线阵CCD上拉曼光谱的获取。荧光显微成像系统应用光学成像原理,通过调节凹透镜与405 nm的激发光之间的距离,使激发光通过物镜均匀的照射到样品之上,样品激发出的荧光,通过物镜,带反反射镜,二向色镜,滤波片与相应的凹透镜,最后成像到面阵CCD上。改进传统便携式拉曼光谱检测系统光路并选用相应波段的带反反射镜与焦距20倍的物镜完成拉曼光谱检测系统与荧光显微成像系统的耦合。为了减少两路系统之间的相互影响选用合适的二向色镜以及滤波片,在提高耦合系统获取数据的准确性中有着重要的作用。该系统通过对反应之后的液相生物芯片进行拉曼光谱检测,以完成对每个编码玻片的定性识别,即解码;同时激发反应后液相生物芯片的荧光并采集荧光强度图,根据每个解码玻片上的荧光强度值完成对目标检测物的定量分析。区别于传统荧光编码液相生物芯片, 拉曼光谱编码具有稳定性更强,光谱分辨率更高等优点。该光学系统集拉曼光谱检测系统与荧光显微成像系统于一体,解决了目前未有基于拉曼编码的液相生物芯片的检测系统的问题,并且可同时对多种目标物进行识别和定量分析,提升了实验结果的准确性。     

Review of Fluorescence Suppression Techniques in Raman Spectroscopy

Abstract

Raman spectroscopy is an important and powerful technique for analyzing the chemical composition of biological or nonbiological samples in many fields. A serious challenge frequently encountered in Raman measurements arises from the existence of the concurrent fluorescence background. The fluorescence intensity is normally several orders of magnitude larger than the Raman scattering signal, especially in biological samples. Such fluorescence background must be suppressed in order to obtain accurate Raman spectra. Several different techniques have been explored for this purpose. These techniques could be generally grouped into time-domain, frequency-domain, wavelength-domain, and computational methods in addition to various Raman enhancement techniques and other unconventional methods. This review briefly describes the fundamental principles of each group of methods, reports the most recent advances, and makes comparison across those major categories of techniques in terms of cost and performance in a hope to guide interested readers to select proper methods for specific applications.