Mid-infrared Optical Frequency Comb-based Fourier Transform Spectrometer for Broadband Molecular Spectroscopy

Optical frequency combbased Fourier transform spectroscopy has the features of broad spectral bandwidth,high sensitivity,andmultiplexed trace gas detection,which has valuable application potential in the fields of precision spectroscopy and trace gas detection.Here,we report the development of a mid-infrared Fourier transform spectrometer based on an optical frequency comb combined with a Herriott-type multipass cell.Using this instrument,the broadband absorption spectra of several important molecules,including methane,acetylene,water molecules and nitrous oxide,are measured by near real-time data acquisition in the 2800-3500 cm^(-1)spectral region.The achieved minimum detectable absorption of the instrument is 4.4×10^(-8)cm^(-1)·Hz^(-1/2)per spectral element.Broadband spectra of H_(2)0 are fited using the Voigt profile multispectral fitting technique and the consistency of the concentration inversion is 1%.Our system also enables precise spectroscopic measurements,and it allows the determination of the spectral line positions and upper state constants of N_(2)O in the(0002)-(1000)band,with results in good agreement with those reported by Toth[Appl.Opt.30,5289(1991)].

On-Line Measurement of the Chemical Oxygen Demand in Wastewater in a Pulp and Paper Mill Using Near Infrared Spectroscopy

Although near infrared (NIR) spectroscopy has been evaluated for numerous applications, the number of actual on-line or even on-site industrial applications seems to be very limited. In the present paper, the attempts to produce online predictions of the chemical oxygen demand (COD) in wastewater from a pulp and paper mill using NIR spectroscopy are described. The task was perceived as very challenging, but with a root mean square error of prediction of 149 mg/l, roughly corresponding to 1/10 of the studied concentration interval, this attempt was deemed as successful. This result was obtained by using partial least squares model regression, interpolated reference values for calibration purposes, and by evenly distributing the calibration data in the concentration space. This work may also represent the first industrial application of online COD measurements in wastewater using NIR spectroscopy.

Performance Comparison of Long-Wave Infrared Imaging Spectrometer Between Dyson Form and Offner Form

In view of the difficulties in traditional long-wave infrared imaging spectrometer which is hard to realize a high signal-to-noise ratio and miniaturization as well under the weak remote sensing signal,Offner convex grating spectrometer and Dyson concave grating spectrometer,both having concentric structure,are designed and analyzed in the band of 8-12 μm. The diffraction angle expressions of the two spectrometers are obtained and the diffraction characteristics are acquired. Both of the spectrometers are designed in Zemax environment under different F-numbers and different grating constants with the same slit,spatial resolution,spectral resolution and detector. The results show that Dyson grating spectrometer possesses the advantages of higher throughput and smaller volume, and Offner grating spectrometer possesses the advantage of more accessible material and the absence of chromatic aberration. The differences between Dyson form and Offner form show that the former is a better choice in the long-wave infrared imaging spectrometer.

Study on the Authenticity of Identification Methods in White Spirit by Infrared Spectrometer

This experiment studies on the used infrared spectroscopy to establish technology methods for liquor identification methods, as well as offers the science data for establishment of the fingerprint in white spirit. The results have shown that using near-infrared spectroscopy analysis of liquor has the obvious features such as strong specificity, good reproducibility, simple operation, and finally confirmed that it is an authentic and ideal method for identification in white spirit.

Application of Portable Near-Infrared Spectrometer for Analysis of Organic Carbon in Marine Sediments

The performance of a portable near-infrared (NIR) spectrometer to determine organic carbon (OC) in marine sediments was evaluated. The NIR reflection spectra of 180 samples in the range 950 - 1650 nm were acquired using an ultra-compact spectrometer. NIR spectroscopy combined with the partial least squares (PLS) regression and Savitzky-Golay (SG) smoothing was successfully applied to rapid and reagent-free determination of OC. Using the PLS-SG model with 1nd order derivative, 2th polynomial and eleven smoothing points, the root-mean-square errors (RMSEPM) and correlation coefficients (RP,M) of prediction for modeling were 0.073% and 0.894, respectively, the root-mean-square errors (RMSEPV) and correlation coefficients (RP,V) of prediction for validation were 0.075% and 0.883, respectively. Results showed that the small portable NIR instrument achieved well prediction effect for the analysis of OC in marine sediments, which had advantages of rapid, easy to carry and operate suitable for large-scale applications to analyze marine sediments.

Spectral Correction Method of Multi-Channels Near-Infrared Spectrometer and Applications

Near-infrared (NIR) spectrometer based on semiconductor lasers can combine light source and splitter into one, which is an important direction for development of miniature instruments. In order to avoid random interference caused by inconsistency between light sources, the novel evaluation indicators for global stability of multi-channels spectral system were proposed based on the correlation between dynamic deviation spectra of any two channels. The NIR analysis of moisture for corn powder samples based on the partial least squares combined with Savitzky-Golay (SG) smoothing was taken as an example, and a spectral correction method for enhancing prediction performance of multi-channels spectral system was further provided using above evaluation indicators. The experiment results showed that the global stability evaluation indicators significantly increased after SG smoothing correction. Meanwhile, the root-mean-square errors of prediction for corn moisture reduced from 0.373 to 0.283 (%), and the correlation coefficient between predicted and actual values was improved from 0.702 to 0.855. The above results indicated that by improving global stability indicators, the prediction ability of multi-channels spectral system can be improved. The proposed method provided a valuable reference for designing multi-channels diminutive spectrometer with high prediction performance, which had significance for large-scale application of NIR technology.

Moisture content in raw rubber sheet analyzed by transflectance near infrared spectroscppy

Moisture content is an important trait for rubber sheet trading system.Therefore,a calibrationequation for predicting moisture content was created by near infrared(NIR)technique in order todevelop a more fair trading system in Thailand.Spectra were recorded in two systems.One wasmeasurement on each rubber sheet and the other was on a pile of sheets.Both were[measured by ahandheld NIR spectrometer in the short wavelength region(700-1100 nm)in the transflectancemode using Teflon as a diffuse refector.The spectra showed the peak at about 900 nm whichbelongs to isoprene,the major component of rubber sheet.Pretreatment with second derivativewas applied to remove baseline shift effect occurring due to thickness differences on each rubber sheet.From validation results,moisture contents predicted by single sheet system were moreaccurate than a pile of sheet system with standard error of prediction(SEP)=0.39 %and bias of-0.07%,and they were not significantly diferent from the actual values at 95%confidence.As aresult,determining moisture content in each rubber sheet by a handheld NIR,spectrometerprovided accurate values,easy and rapid operation.

银耳多糖对麦醇溶蛋白纳米体系的影响及复合物的特性研究

该研究是以提高麦醇溶蛋白(gliadin,Gli)纳米颗粒(gliadin nanoparticles,GNPs)稳定性为目标,利用银耳多糖(Tremella fuciformis polysaccharides,TFPs)的乳化性能,探究TFPs添加量对GNPs稳定性的影响。采用反溶剂法制备银耳多糖和麦醇溶蛋白复合载体颗粒(gliadin-Tremella fuciformis polysaccharides composite nanoparticles,G/T NPs),并利用纳米粒度仪、傅里叶变换红外光谱仪、热场发射扫描电镜对G/T NPs的粒径和电位、相互作用、微观结构进行分析。结果表明,TFPs和Gli之间通过静电作用力和氢键作用力相结合,形成GNPs在内、TFPs外层附着的复合颗粒;TFPs的添加能够有效提高GNPs体系的稳定性,减少颗粒之间的聚集,制得的G/T_(4∶1)NPs的平均粒径、多分散指数(polydispersion index,PDI)、ζ-电位分别为(198.5±2.6)nm、0.269±0.005、(36.7±0.6)mV,且具有pH响应性。该研究为后续构建疏水营养成分的包埋和运载体系奠定了基础。

手持式近红外光谱仪测定梨三种品质指标通用模型建模方法研究

梨是生活中非常常见的水果,梨的糖度、酸度(pH)、硬度是评价梨品质的重要指标。近红外光谱技术因快速、无损和高效等优点,广泛应用于检测水果品质指标。手持式近红外光谱仪可以应用于现场无损检测梨品质,梨的大小不同会对梨的光谱和建模产生一定影响。因此,采集大小不同的5个品种梨果(雪梨、红香酥、蜜梨、红肖梨、酸梨)的近红外光谱,最大的雪梨平均赤道周长27.64 cm,重量为362.84 g,最小的蜜梨平均赤道周长18.35 cm,重量为112.67 g,共197个样品。光谱范围为900~1700 cm^(-1),并在梨的赤道上选取三个点测量梨果的可溶性固形物、酸度(pH)与硬度三个化学指标。采集光谱发现,小梨吸光度较大,而大梨吸光度较小。采用三点平均光谱代表样品光谱和一阶导预处理,改善了光谱的一致性,解决了样品不均匀性、不同梨大小不同等因素的影响。线性回归模型PLS可溶性固形物、酸度(pH)和硬度的校正集决定系数依次为0.7394、0.9335、0.8866,预测集决定系数依次为0.7559、0.8734、0.7874,校正集RMSEC依次为0.5504、0.1941、0.5181。预测集RMSEP依次为0.6564、0.2420、0.6692。非线性回归LSSVM模型可溶性固形物、酸度(pH)和硬度的校正集决定系数依次为0.9763、0.9999、0.9960,预测集决定系数依次为0.9234、0.9777、0.9394,校正集RMSEC依次为0.1949、0.0033、0.0894。预测集RMSEP依次为0.3169、0.1089、0.3613。对比线性算法和非线性算法,LS-SVM建模效果明显优于PLS,LS-SVM算法适用于更多的品种、更宽的品质指标范围的样品预测,模型的准确度和稳定性有了显著提高,可以建立不同品种大小的梨的通用模型。手持式近红外光谱仪可用于梨果的糖度、硬度和pH值的快速无损高效检测,并摆脱了实验室的限制,可以实现现场快速检测。

基于双光栅和柱透镜的高分辨率近红外微型光谱仪

因为便携、低成本、集成化等优势,微型光谱仪已经成为光谱仪技术发展的重要趋势,其中工作波段在近红外的微型光谱仪,在光纤传感和解调、光纤通信等领域有着非常广泛的应用。但目前的近红外微型光谱仪普遍存在分辨率低、成本高、体积大不便于携带等问题,为此,提出了一种独特的基于双光栅和柱透镜的微型光谱仪结构,开展了理论和实验研究。相对于传统的微型光谱仪结构,新的设计主要有三个特征:使用光纤代替入射狭缝,以减少光能损失;采用双光栅将光束进行二次衍射;使用柱透镜以改变线阵CCD阵列表面的成像尺寸。首先,利用Zemax软件进行了光学设计和仿真分析,光谱范围为1525~1570 nm,光学系统结构在66 mm×40 mm×24 mm的体积范围内,光谱分辨率理论上达到0.2 nm,比未加柱透镜的结构提升了2.5倍。然后,根据理论分析,选购了合适的光电器件进行了系统封装,与匹配的电路模块结合,实现了微型光谱仪的光谱检测功能。光谱仪的光学系统安装在66 mm×40 mm×30 mm的体积范围内,实际测量的光谱分辨率为0.215 nm,与理论结果较为吻合。进一步地,搭建了一套基于该微型光谱仪的光纤光栅温度传感测量系统,该微型光谱仪作为信号解调仪,选择了四个中心波长分别为1534、1538、1542和1545 nm的光纤光栅作为传感器,温度在0~50℃范围内以1℃为间隔连续变化,最终实现了温度实时测量和信号解调,系统温度灵敏度分别达到9.58、9.68、9.69和9.6 pm·℃^(-1),验证了该微型光谱仪的高分辨率和高可靠性。研制的微型光谱仪的子组件可以固定在外壳上,系统内部无可移动元器件,体积小、分辨率高、稳定性好,可应用于其他诸如物质浓度分析、传感信号测量等需要高分辨光谱分析的场合。

T/CIS 17006-2022《傅立叶变换近红外光谱仪通用技术规范》主要技术指标解析

2022年12月1日中国仪器仪表学会正式发布了团体标准T/CIS 17006-2022《傅立叶变换近红外光谱仪通用技术规范》,这是国内首个专门面向近红外光谱仪的标准。为了方便广大用户更好地理解和贯彻执行新标准,本文对该标准中涉及到的技术指标进行了详细解读。

基于移动平台的便携式FTIR灾害现场气体检测技术

傅里叶红外光谱技术(FTIR)的引入极大地提升了气体的检测速度和准确性。然而在石油化工泄露和爆炸、森林火灾等突发危险现场,存在着人力无法现场检测的情况。为了应对这种场景,开发了基于移动平台的便携式FTIR灾害现场气体检测方法。通过将云服务器和树莓派的优势相结合实现远程操作移动平台,将搭载便携式FTIR光谱仪的移动平台远程操作驶入现场,并及时通过4G/5G模块传回现场位置数据、视频数据和光谱气体浓度数据。最后,在野外基地利用该平台进行了实测,对CO_(2)、CO、SO_(2)、C_(6)H_(6)等多种污染气体进行了检测,结果验证了该系统在野外工况下的可靠性。本工作为FTIR光谱仪或其他光谱类检测系统在移动平台上的集成应用提供了思路和解决方案。

基于双曲面弯晶技术的X射线荧光光谱仪对塑料快递袋检验分类

目的解决部分塑料快递袋轻元素占比高、元素种类少、常规X射线荧光光谱难以有效区分的缺点。方法利用红外光谱和基于双曲面弯晶技术的X射线荧光光谱仪对7个快递公司,不同地区、不同批次共36个样品进行成分分析和元素含量分析。首先,利用红外光谱对样品基体进行区分,然后再根据元素含量进行组内细分,最后将分类结果作为定类带入梯度提升树模型中,并进行模型稳健性验证。结果样品被红外光谱分为2组,再根据钛元素与硫元素含量将2组细分为5类,梯度提升树模型经过参数优选后准确率为94.2%。结论该方法能够根据样品基体与填料的差异性快速分类并预测所属种类,填补常规X射线荧光光谱检验的空缺,为未知塑料快递袋溯源分类提供了一种新的侦查思路和技术手段。

安息香的合成与表征——一个有机化学综合性实验

安息香缩合反应作为一个发展较为成熟的反应,已经被广泛运用于化学工业中。该实验以苯甲醛为原料,维生素B1作为催化剂,在pH=9~10、乙醇和70℃恒温水浴条件下,苯甲醛经缩合产生安息香。利用薄层色谱法(TLC)监测反应和反应液的核磁共振氢谱定量分析产率。本实验通过红外光谱、气质联用仪、核磁共振氢谱、碳谱对产物图谱的分析,使学生更深刻地理解有机化学、仪器分析等课程所学的波谱理论知识。

当归痛风方对小鼠高尿酸血症肾病的FTIR研究

傅里叶变换红外光谱(FTIR)是鉴别物质和分析物质结构的有效手段,可对样品进行定性和定量分析,广泛应用于医药化工等众多领域。FTIR作为一种操作简便、实用、准确率高和费用低的鉴别方法,如今已经普遍应用于各种药品检验中,而有关其应用于药理研究中还非常少,目前仅有采用红外光谱分析法对各种肿瘤组织进行研究的报道。高尿酸血症肾病是人体血尿酸升高后,过高的尿酸负荷超过肾脏的清除能力,尿酸结晶沉积于集合管、肾盂和尿道等。采用FTIR技术评价高尿酸血症肾病模型,并评价药物的药效,具有一定的可行性。该实验为探讨FTIR评价高尿酸血症肾病模型和当归痛风方疗效的科学性,将60只KM小鼠随机分为6组,正常对照组、模型组、阳性对照组和当归痛风方低、中、高组,采用氧嗪酸钾复制高尿酸血症肾病模型,灌胃当归痛风方,检测血清UA、尿液UA、血清CRE、尿液CRE、血清IL-1β和肾脏IL-1β、肾脏FTIR谱图等,并观察肾脏的病理变化。结果表明模型组各项指标与正常组比较有统计学意义(p<0.05),当归痛风方高剂量组的血清UA、血清CRE、血清IL-1β和肾脏IL-1β等与模型组比较且有统计学意义(p<0.05)。当归痛风方高剂量组肾脏的病理变化有所改善,无炎性细胞浸润,管腔内无管型,说明对肾损伤具有保护作用。各组FTIR谱有明显的差异,模型组的强度均低于正常组,阳性对照组和当归痛风方高剂量组谱接近正常组,进一步说明当归痛风方对肾损伤具有保护作用。研究表明FTIR可以作为一种简便快捷灵活经济的评价动物模型及药物疗效的方法之一,也为高尿酸血症肾病模型及有效药物的筛选提供了一个有意义的技术手段。该实验拓展了FTIR检测方法的使用范围。

基于LabVIEW的透射转镜式傅里叶变换光谱分析软件设计

为满足透射转镜式傅里叶变换红外光谱仪的数据采集、非线性拟合补偿、信号预处理和傅里叶光谱反演等测试需求,设计了一套基于LabVIEW的集数据采集和信号分析为一体的透射转镜式傅里叶光谱分析软件。该软件通过调用NI数据采集卡的物理通道接口来采集干涉信号幅度随时间变化的干涉图数据,并通过信号处理程序复原红外信号的频谱信息,可实现波形文件的自动存储和数据处理重要流程的可视化,适合在工控机上应用。测试面源黑体辐射源的辐射光谱曲线,利用聚苯乙烯的吸收光谱测试波长准确性,并利用水蒸气的光谱曲线测试光谱半高宽。采用本文设计的光谱分析软件,复原出了红外信号的光谱分布,实现了0.40%的波长准确性、0.88cm^(-1)的光谱分辨率,验证了系统的可用性。

近红外光谱仪在白酒酒醅检测中的研究与应用

固态酒醅传统检测存在预处理繁琐、检测时间长、工作量重、药品消耗量及废液产生量大等问题,同时因检测时间长、反馈检测结果滞后,不能达到指导制酒车间生产的目的。为了提高酒醅的检测效率及检测速度,本研究采用近红外光谱仪和偏最小二乘法结合,对酒醅的水分、酸度、淀粉、还原糖等理化指标建立分析模型。模型建立成熟后,其准确度、重复性完全能满足实际生产需要。近红外法与传统检测方法相比有以下优点:能有效的缩短检测时间、免去传统检测中复杂的操作步骤、无化学品消耗、不产生废液等。模型建立成熟后,能实现样品快速扫描,很大程度上提升了工作效率。

基于近红外拉曼光谱结合LSTM-CNN模型提高牡丹籽油掺假浓度的预测精度

为建立一种适用于市场在线监测玉米油掺假牡丹籽油的方法,研究了便携式785拉曼光谱技术应用于一线市场质检的潜力,制备了525个玉米油掺假牡丹籽油的油品,评估了每种混合油品便携式近红外拉曼光谱数据集的稳定性和21种混合油品拉曼光谱谱峰的差异性,分析了拉曼光谱谱峰的振动归属。随机选择16种混合油品的拉曼光谱数据集用于训练定量模型,将剩余的5种混合油品的拉曼光谱数据集用于测试定量模型。牡丹籽油与玉米油的近红外拉曼光谱存在较大差异,根据特征峰位的归属判定,拉曼光谱谱峰差异很好地反映了植物油间的脂肪酸含量差异。提出一种将长短期记忆网络结合卷积神经网络(LSTM-CNN)的模型应用于玉米油掺假牡丹籽油的量化预测,对比了偏最小二乘回归算法的预测效果。结果表明便携式785拉曼光谱的稳定性良好,具备实现对牡丹籽油掺假量的在线、快速量化的性能,且结合LSTM-CNN模型可以实现对玉米油掺假牡丹籽油含量的预测,其模型评价参数决定系数(R^(2))为0.9908,均方根误差(RMSE)为0.0299。便携式近红外拉曼光谱结合LSTM-CNN模型是一种快速、高效、可行的鉴别玉米油掺假牡丹籽油的有效方法。

傅里叶红外光谱仪中高饱和蒸气压有机胺体积分数标定方法

基于有机胺吸收剂的化学吸收法能够有效捕集船舶烟气中的CO_(2),但吸收剂降解失效、挥发泄漏会造成严重的环境问题。虽然傅里叶红外光谱仪能够实时监测挥发的有机胺体积分数,但受限于高饱和蒸气压有机胺类蒸气难标定问题,对胺类体积分数的实际监测精度较低。对此,设计两种傅里叶红外光谱仪中高饱和蒸气压有机胺蒸气体积分数标定方法,分别为固定比例校准算法和基于循环神经网络的序列映射法。结果表明,相较于固定比例法,基于循环神经网络的非线性序列映射法能够实现更好的校准性能,平均绝对误差下降了81.57%,均方误差下降了70.05%,可有效反映船舶碳捕集与封存(carbon capture and storage,CCS)系统对大气环境的影响。

A collinear tandem time-of-flight mass spectrometer for infrared photodissociation spectroscopy of mass-selected ions

An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed laser vaporization supersonic ion source are skimmed and mass separated by a Wiley-McLaren time-of-flight mass spectrometer.The ion of interest is mass selected,decelerated and dissociated by a tunable IR laser.The fragment and parent ions are reaccelerated and mass analyzed by the second time-of-flight mass spectrometer.A simple new assembly integrated with mass gate,deceleration and reacceleration ion optics was designed,which allows us to measure the infrared spectra of mass selected ions with high sensitivity and easy timing synchronization.