消像散型Czerny-Turner成像光谱仪图像变形校正研究

Czerny-Turner结构成像光谱仪像散校正会改变系统焦距,导致图像子午方向和弧矢方向放大率存在差异。分析了两种Czerny-Turner结构成像光谱仪像散校正光路(柱面镜和超环面)像散校正原理,由此提出并推导出两类光谱图像变形校正公式和方法,并总结二者的共同特征。通过理论计算、光线追迹仿真和实际光谱成像测量验证了图像变形校正方法的正确性。同时,该图像校正方法对其他准直光工作条件下离轴结构色散型成像光谱仪图像变形校正研究有借鉴意义。     

超细粉末压片制样X射线荧光光谱测定碳酸岩样品中多种元素及CO_2

粉末压片X射线荧光光谱分析碳酸岩的误差主要来自粒度效应和矿物效应。为消除粒度效应影响,采用超细粉末压片制样准确测定了碳酸岩中的多种元素和CO2。使用德国FRITSCH行星式球磨机,碳化钨研磨介质将碳酸岩进行超细粉碎,为了克服团聚效应,采用了湿法研磨。随颗粒度的减小,样品表面形态更平整、光滑,康普顿散射效应减小。研究了粒度变化对各元素分析线强度的影响,通常荧光强度随粒度减小而增加。当多个组分的颗粒度减小时,S,Si,Mg的强度将增加,Ca,Al,Ti,K的强度将减小,这取决于各自的质量吸收系数。研究了粒度变化对矿物物相组成的影响。计算了各分析元素分析线的穿透厚度,当样品的粒度碎至元素分析线的穿透厚度以下时,荧光强度受粒度的影响减小。实验发现当样品碎至d95≤8μm时,基本消除了颗粒度效应影响,压片法制样,理论α系数、经验系数法结合校正基体效应,可准确测定碳酸岩样品中14个元素,方法的精密度大大改善,除Na2O外,RSD2%。C是超轻元素,荧光产额低且干扰严重。实验采用PX4人工多层膜晶体,粗准直器,X射线荧光光谱可定量测定碳酸岩中的CO2。试验发现C的测量强度随测量次数的增加而增加,且随放置时间的增加而增加(即使在干燥器中存放),因此建议使用新制的样片测定CO2。     

Calibration Procedure of Laser Confocal Micro-Raman SpectrometerSCIEI北大核心CSCD

As a common spectral characterization technique, Raman spectroscopy is widely used and has a specified calibration procedure. Based on laser confocal micro-Raman spectrometer, in this paper, we briefly introduced the principle, configuration and main components of Raman spectrometer. In addition, the calibration procedures were also presented, with an emphasis on the calibration of spectrometer (spectrograph) and that of excitation laser wavelength. On the basis of conventional calibration method, a novel and more accurate method was proposed to obtain the actual excitation wavelength, that is, calibration at the point of Raman shift Delta nu=0. Using this novel calibration method of excitation wavelength, Raman frequency shift values of sulfur were measured, and compared with the standard values from American Society Testing and Materials (ASTM). As a result, the measured values after calibration were consistent with those ASTM values, which indicated that the calibration method is accurate. Thus, a more reasonable calibration procedure of the laser confocal micro-Raman spectrometer was provided.     

空间调制微型傅里叶变换红外光谱仪研究

针对目前环境、医疗、空间、气象、军事及安全等领域对傅里叶变换红外光谱仪微小型化、轻量化及固态化的迫切需求,提出并研究了一种以MOEMS多级微反射镜为核心器件的空间调制微型傅里叶变换红外光谱仪。在理论研究方面,建立了空间调制微型傅里叶变换红外光谱仪的物理模型,探究了该系统的光场分割与空间采样的光学原理;分析了多级微反射镜的衍射效应,提出了一种通过补边抑制衍射噪声抑制方法;进行了多级微反射镜采样误差的分析,并提出了基于最小二乘拟合的修正算法;通过对光源空间相干性、准直系统像差以及入射光场均匀性的分析,确定了光学系统的总体设计指标;通过对多级微反射镜基片加工精度、分束器材料色散特性和膜层透射效率等的计算分析,确定了干涉系统的设计方法与技术参数。在核心技术方面,提出了两个多级微反射镜的3种制作方法,分析了制作误差的来源及对系统性能的影响。通过工艺设计及实验条件探索,分别采用电铸法、真空镀膜法以及斜面倾角叠片法制作了两个多级微反射镜。在系统设计方面,进行了红外准直与缩束系统的光学设计,对整体光机系统进行了建模仿真,分析了杂散光噪声的来源。在图谱处理方面,利用过零采样方式,通过图像分割算法,获取了干涉图采样序列;通过对干涉图序列的插值、补零、延拓与卷积方法,完成了光谱相位误差的校正;通过离散傅里叶变换解调,实现了由干涉图像到信号光谱的数据反演。最后研究了系统光机整体的集成组装技术,并对原理样机进行了实验测试。本文研制的空间调制微型傅里叶变换红外光谱仪的特点在于:取消了动镜驱动机构与采样控制机构,具有微小型与轻量化的特点;干涉图的采样由多级微反射镜完成,其空间采样的方式增加了系统的稳定性与可靠性,实时采样的特点增加了系统的快速性与有效性;多级微反射镜阵列采用MOEMS工艺技术制作,增加了系统的采样精度。该光谱仪系统的结构及制作方法具有自主知识产权,并具有广阔的应用前景。     

Facile residue analysis of recent and prehistoric cook stones using handheld Raman spectrometry

We performed food residue analysis of fire‐cracked rock (FCR) from experimental and prehistoric earth ovens using a handheld Raman spectrometry. Progress in modern optical technology provides a facile means of rapid non‐destructive identification of residue artifacts from archaeological sites. For this study spectral signatures were obtained on sotol (Dasylirion spp.) experimentally baked in an earth oven as well as sotol residue on an experimentally used processing tool. Inulin was a major residue component. The portable handheld Raman spectrometer also detected traces of inulin on experimental boiling stones used to boil commercially obtained inulin. The Raman spectra of inulin and sotol may be useful as signatures of some wild plant residues in archaeology. Spectroscopic analysis of millennia‐old FCR from prehistoric archaeological sites in Fort Hood, TX revealed the presence of residues whose further identification requires improvement of current optical methods. Copyright © 2014 John Wiley & Sons, Ltd.     

A multimodal spectrometer for Raman scattering and near-infrared absorption measurement

Raman and infrared (IR) spectroscopy are complementary spectroscopic techniques. However, measurement of Raman and IR spectra are commonly carried out on separate instruments. A dispersive system that enables both Raman spectroscopy and NIR spectroscopy was designed, built, and tested. The prototype system measures spectral ranges of 2600–300 cm⁻¹ and 752–987 nm for Raman and NIR channels, respectively. A wavelength accuracy better than 0.6 nm and spectral resolution better than 1 nm (14.4 cm⁻¹ for Raman channel) could be achieved with our configuration. The linearity of spectral response was better than 99.8%. The intensity stability of the instrument was found to be 0.7% and 0.4% for Raman and NIR channels, respectively. The performance of the instrument was evaluated using binary aqueous solutions of ethanol and ovalbumin. It was found that ethanol concentrations (2–10%) could be predicted with a root mean squared error of prediction (RMSEP) of 0.45% using Raman peak height at 882.2 cm⁻¹. Quantification of ovalbumin concentration (8–16 g/L) in aqueous solutions and in denatured states yielded RMSEP values of 1.05 g/L and 0.74 g/L, respectively. Using concentration as external perturbation in two-dimensional correlation spectroscopy (2DCOS), heterospectral correlation analysis revealed the relationship between NIR and Raman spectra.     

Targeted analysis of multiple pharmaceuticals,plant toxins and other secondary metabolites in herbal dietary supplements by ultra-high performance liquid chromatography–quadrupole-orbital ion trap mass spectrometry

In this study, an ultra-high performance liquid chromatography–quadrupole-orbital ion trap mass spectrometry (UHPLC–Q-orbitrap MS) method was developed and validated for simultaneous determination of 96 pharmaceuticals, plant toxins, and other plant secondary metabolites in herbal dietary supplements. Target analytes were extracted from samples using the QuEChERS (quick easy cheap effective rugged safe) procedure. The instrument was operated in full MS–data dependent tandem mass spectrometry (full MS–dd-MS/MS) acquisition mode which enabled collection of quantitative high resolution (HR) full mass spectral data and confirmatory HR MS/MS data in a single run. The method provided excellent selectivity in both full MS and dd-MS/MS mode. Under optimized collision energy settings, product ion spectra containing both precursor and two or more product ions were obtained for most of the analytes. Limits of detection (LODs) and limits of quantification (LOQs) for the method differed significantly for the examined matrices. LODs ≤ 10 μg kg⁻¹ and LOQs ≤ 50 μg kg⁻¹ were obtained for 48 to 81% of target compounds across five different matrices. With the exception of highly polar analytes, the optimized QuEChERS extraction procedure provided acceptable recoveries in the range 70%–120%. The precision of the method, characterized as the relative standard deviation (RSD, n = 5), was ≤25% and ≤18% at spiking concentrations of 50 μg kg⁻¹ and 500 μg kg⁻¹, respectively. Because of variations in matrix effects in extracts of herbal dietary supplements that differed in composition, the method of standard additions and an approach based on dilution of matrix components followed by quantification using solvent standards were applied for quantification. The procedure was used to examine commercial dietary supplements for the 96 analytes of interest. To the best of our knowledge, this is the first report of an integrated analysis and quantification of this wide range of compounds.     

Validation of a qualitative screening method for pesticides in fruits and vegetables by gas chromatography quadrupole-time of flight mass spectrometry with atmospheric pressure chemical ionization

A wide-scope screening method was developed for the detection of pesticides in fruit and vegetables. The method was based on gas chromatography coupled to a hybrid quadrupole time-of-flight mass spectrometer with an atmospheric pressure chemical ionization source (GC-(APCI)QTOF MS). A non-target acquisition was performed through two alternating scan events: one at low collision energy and another at a higher collision energy ramp (MS^E). In this way, both protonated molecule and/or molecular ion together with fragment ions were obtained in a single run. Validation was performed according to SANCO/12571/2013 by analysing 20 samples (10 different commodities in duplicate), fortified with a test set of 132 pesticides at 0.01, 0.05 and 0.20 mg kg⁻¹. For screening, the detection was based on one diagnostic ion (in most cases the protonated molecule). Overall, at the 0.01 mg kg⁻¹ level, 89% of the 2620 fortifications made were detected. The screening detection limit for individual pesticides was 0.01 mg kg⁻¹ for 77% of the pesticides investigated. The possibilities for identification according to the SANCO criteria, requiring two ions with a mass accuracy ≤±5 ppm and an ion-ratio deviation ≤±30%, were investigated. At the 0.01 mg kg⁻¹ level, identification was possible for 70% of the pesticides detected during screening. This increased to 87% and 93% at the 0.05 and 0.20 mg kg⁻¹ level, respectively. Insufficient sensitivity for the second ion was the main reason for the inability to identify detected pesticides, followed by deviations in mass accuracy and ion ratios.     

直读光谱法测量镁合金中锰含量的测量不确定度评定

根据GB/T13748.21-2009镁及镁合金化学分析方法(光电直读发射光谱分析方法测定元素含量)对镁合金中锰元素含量进行了分析,对锰含量测量的不确定度来源进行了分析,并对测量过程中产生的不确定度进行了评定.此外,指出了该方法影响锰元素测量不确定度的主要原因,以期为镁合金中锰元素含量的光谱分析提供参考.     

Self-broadening coefficients in the ν4 band of CH4 by diode-laser spectroscopy

With a diode-laser spectrometer, we have measured self-broadening coefficients of 42 lines of the P-, Q- and R-branches in the ν₄ fundamental band of CH₄ at room temperature, with J values ranging between 1 and 12. For the determination of self-broadening parameters, we have fitted to the experimental lineshape two theoretical line profiles: the Voigt profile taking into account Doppler and collisional broadenings, and the hard collision model developed by Rautian and Sobel’man incorporating Dicke narrowing.