采用多光程长建模方法检测血液成分含量

为了提高近红外光谱血液成分含量分析模型的预测精度,利用多个光程长(optical path length,OPL)共同参与建模的方法进行血糖等6种血液成分的定量分析。通过微米位移机构实现不同光程长血液光谱的测量,由全自动生化分析仪给出生化成分分析结果,并出具化验单。采用偏最小二乘法(PLS2)进行血液的近红外光谱建模及预测。由于血液光谱存在显著的非线性特征,不同光程长的血液样本的等效吸收系数不同,同一波长不同光程长(0.20~1.25 mm)测得的血液光谱互不相关。主动把非线性特性作为一种测量手段引入,不再利用单个的最佳光程长建模,而是用各个血液组分对应的多个最佳光程长的近红外光谱同时参与建立校正模型,进行血液成分的分析预测。研究结果表明,多光程长建模方法用于血液成分含量分析,可提高血液成分校正模型的预测精度。     

近红外光谱技术在液化石油气检测中的应用研究

本研究采用实验室近红外光谱仪测定气态液化石油气的组成,自行研制了可让气流稳定流过的比色皿,并制作了配套的铝合金样品槽,研究了光程、光谱波段、扫描时间等因素对气态液化石油气近红外模型的影响,确定了最佳的实验参数,并对液化石油气各组分的近红外模型进行了优化.结果表明:近红外光谱技术结合自制比色皿适用于液化石油气组成分析,所...     

多模型共识偏最小二乘法用于近红外光谱定量分析

将多模型共识偏最小二乘法用于近红外光谱定量分析。利用随机抽取的训练子集建立一系列偏最小二乘模型,选取其中性能较好的部分模型作为成员模型,用这些成员模型来预测未知样品。将该方法用于一组生物样本的近红外光谱与样品中人血清白蛋白、γ-球蛋白以及葡萄糖含量之间的建模研究,并与单模型偏最小二乘法了进行比较。结果 PLS对独立测试集中三种组分进行50次重复预测的平均RMSEP分别为0.1066,0.0853和0.1338,RMSEP的标准偏差分别为0.0174,0.0144和0.0416;而本方法重复预测的平均RMSEP分别为0.0715,0.0750和0.0781,RMSEP的标准偏差分别为0.0033,0.2729×10-4和0.0025。     

蜂蜜中果糖和葡萄糖近红外检测的差异性分析及优化研究

采集了来自全国20种单植物源和其它多植物源的101份的蜂蜜样品,分别运用傅立叶型近红外光谱仪采用光纤透反射(800～2500nm,2mm光程)和透射(800～1370nm,20mm光程)采集方式获得近红外光谱,来预测蜂蜜中结构和含量都很相近的果糖和葡萄糖含量。结果发现,两种测量方式下果糖、葡萄糖的预测准确度存在着较大的差异。为了分析这种差异产生的原因,采用支持向量机分析其非线性信息,采用遗传算法分析其特征波长,结果表明:这种差异主要来自两种糖分特征波长分布不同所导致。通过对两种糖分的检测方案进行优化,得出在利用近红外光谱技术检测蜂蜜中葡萄糖成分含量时应尽量采集短波区、长光程的光谱,或者对全谱区、短光程的光谱,进行特征波长的提取,避开水分的干扰,从而提高其预测精度;而对于果糖,则应尽量采集全谱区、短光程的光谱;采用常用线性定量建模方法PLSR就可以得到很好的预测模型,非线性的支持向量机模型未能明显提升模型性能。     

近红外光谱用于过氧化氢含量的定量分析研究

用长波近红外光谱仪（傅里叶变换,InGaAs检测器）和短波近红外光谱仪（光栅分光,CCD检测器）对比研究了25％～30％过氧化氢水溶液中过氧化氢含量的定量分析方法。结果表明,应用短波近红外光谱结合长光程样品池对25％-30％过氧化氢水溶液样品中过氧化氢含量进行定量分析,可以显著减少过氧化氢分解对定量分析的干扰,使定量分析的准确度和重复性显著提高。短波近红外光谱定量分析模型RMSECV和RMSEP分别为0．06和0．05;长波近红外光谱定量分析模型RMSECV和RMSEP分别为0．10和0．09。     

可见-近红外光谱法鉴定热液蚀变矿物种类及相对含量

采用可见-近红外光谱法鉴定热液蚀变矿物种类及相对含量。介绍了热液蚀变矿物的可见-近红外光谱吸收特征,采用可见-近红外光谱法和X射线衍射法对热液蚀变矿物样品进行分析。结果表明:可见-近红外光谱法在热液蚀变矿物种类鉴定方面与X射线衍射法分析方法结果比较接近。     

多种分子光谱快速分析黄芩中的黄芩苷含量

为考察根据不同类型光谱信息进行黄芩质量快速分析的适应性,采用高效液相色谱(HPLC)法测定了73批黄芩样品中的黄芩苷含量并作为y值,以各样品的近红外、紫外-可见光谱及包含紫外、可见及近红外的多源复合光谱信息作为x值;根据各类光谱信息分别采用偏最小二乘回归(PLSR)与K最近邻样本保形映射(KNN-KSR)方法进行样品中黄芩苷的预测,根据验证集样本真实值与预测值的均方根偏差(RMSEP)、平均相对误差(MRE)与相关系数(R)评价预测精度。结果表明,采用KNN-KSR方法根据各类光谱信息预测黄芩苷时,各项指标均优于PLSR方法的结果;其中基于近红外光谱对黄芩苷的分析结果最好,紫外-可见光谱次之,基于多源复合光谱信息对黄芩苷的预测误差最大,但其MRE仍在6%以下,可满足工业分析的精度要求。由于多源复合光谱仪具有体积小、重量轻、成本低及便携等优点,通过优化仪器波长范围及建模方法,有望改进该仪器的分析精度,使之适应更多药材现场采购的快速检测及后续产品的质量分析与监控需求。     

近红外光谱法快速测定柴胡提取过程中的药效成分

利用近红外光谱(NIRS)技术对柴胡提取过程中的药效成分进行快速定量分析。共收集126个柴胡提取液样品,采用紫外-可见分光光度法测定总黄酮和多糖的含量,高效液相色谱法(HPLC)测定柴胡皂苷A及柴胡皂苷D的含量,以透射模式采集提取液的近红外光谱,运用偏最小二乘法(PLS)分别建立了近红外光谱与4种药效指标参考值之间的定量校正模型,并采用不同的预处理方法、光谱波段和主因子数对模型进行优化。结果表明,总黄酮、多糖、柴胡皂苷A和柴胡皂苷D 4种定量模型的近红外预测值与参考值之间的拟合性良好,模型预测精度较高,其中预测集相关系数(RP)均大于0.9;预测集误差均方根(RMSEP)分别为3.46 μg/mL、0.743 mg/mL、1.53 μg/mL、0.406 μg/mL;预测集相对偏差(RSEP)分别为1.65%、8.28%、5.74%、7.52%。该研究证实了NIRS结合PLS可成功应用于监测柴胡提取液中药效成分的含量变化,且方法具有快速、准确、无损和环保的特点。     

用人工神经网络-近红外光谱法测定冬虫夏草中的甘露醇

提出了用近红外漫反射光谱技术快速分析发酵冬虫夏草菌粉中甘露醇含量的新方法。采用比色法测定样品中的甘露醇，其含量范围为8．082％-14．548％。在7501．7-6097．8cm^-1与5453．7-4246．5cm^-1波段，分别采用PCR、PLSR和BP神经网络方法建立了样品近红外光谱的一阶微分光谱与其甘露醇含量之间的相关模型。BP神经网络模型的内部交叉验证误差均方根为0．475，预测误差均方根为0．608，均优于PCR和PLSR的处理结果。这表明，BP神经网络法对非线性检测对象具有较好的建模效果，可用于中药近红外光谱分析的非线性校正。     

基于近红外光谱的食用植物油中反式脂肪酸含量快速定量检测及模型优化研究

利用近红外光谱技术对食用植物油中反式脂肪酸(Trans fatty acids,TFA)含量进行快速定量检测,并通过波段选择、预处理方法、变量筛选及建模方法对TFA含量预测模型进行优化.采用AntarisⅡ傅里叶变换近红外光谱仪在4000~10000 cm-1光谱范围采集98个食用植物油样本的近红外透射光谱,然后采用气相色谱法测定TFA的真实含量.首先,对样本原始光谱进行波段、预处理方法优选;在此基础上,采用竞争自适应重加权法(Competitive adaptive reweighted sampling,CARS)筛选TFA相关的重要变量,最后应用主成分回归、偏最小二乘和最小二乘支持向量机方法分别建立食用植物油中TFA含量的预测模型.研究结果表明,近红外光谱技术检测食用植物油中的TFA含量是可行的,优化后的最佳预测模型的校正集和预测集R2分别为0.992和0.989,RMSEC和RMSEP分别为0.071%和0.075%.最佳预测模型所用的变量仅26个,占全波段变量的0.854%.此外,与全波段偏最小二乘预测模型相比,其预测集R2由0.904上升为0.989,RMSEP由0.230%下降为0.075%.由此表明,模型优化非常必要,CARS能有效筛选TFA相关的重要变量,极大减少建模变量数,从而简化预测模型,并较大提高预测模型的精度和稳定性.     

可见-近红外傅里叶变换光谱仪

本文介绍了我们研制的波长范围400至1000nm的可见一近红外傅里叶交换光谱仪。通过四倍频电路使激光条纹间隔四等分,给出158.2nm等光程差间隔进行干涉图采样。使用Apple Ⅱ微计算机控制仪器操作,数据采集和数据处理。对光谱测量结果进行了讨论。     

Electrochemical preparation of polythiophene via 2,5-bis(trimethylsilyl)thiophene

Electrochemical polymerization of 2,5-bis(trimethylsilyl) thiophene produced highly conducting films which showed infrared spectra, visible-near infrared absorption spectra, and cyclic voltammograms identical to films prepared from thiophene. Elemental analysis indicated that almost all silicon atoms were eliminated during the electrochemical polymerization. However, scanning electron microscopy showed a morphological difference between the films from 2,5-bis(trimethylsilyl)thiophene and from thiophene. The electrochemical polymerization of bis(2-thienyl)dimethylsilane, 1,2-bis(2-thienyl)tetramethyldisilane, and bis(2-thienyl)diphenylsilane also produced polythiophene films having unique morphologies quite different from the conventional ones. These findings indicate that these electrochemical procedures must be useful for preparation of new conjugated polymers. © 1992 John Wiley & Sons, Inc.     

Infrared transmission equations in a five media system: gas and liquid

Equations are proposed for transmission cells in the presence of multiple reflections and absorption which generate unwanted fringes. These influence adversely band intensity measurements. The infrared (IR) spectra generated with these equations are compared successfully with experimental spectra obtained with BaF₂, ZnSe, and Si windows in parallel mount formation having μm range air gaps. Equations are extended for integration of a variable path length such as in wedge shaped cells that are used to mitigate fringe formations but generate other odd problems such as path length determination. These equations allow the evaluation of the transmission obtained from boxcar cells whose parallelism is a little offset. This phenomenon modifies the fringe intensities. The proposed equations were used to calculate the IR spectra of pure liquid D₂O between BaF₂ and ZnSe windows with path lengths of around 25 μm and compared with experimental spectra. Since the fit was very good it indicates that the proposed equations give better optical properties of pure liquids than that presently available. This is important for liquid used as standards and in particular water used here as reference.     

Photostability of bacteriochlorophyll a and derivatives: potential sensitizers for photodynamic tumor therapy

The photostabilities of bacteriochlorophyll a and several of its derivatives, which are of interest as potential sensitizers in photodynamic tumor therapy, were investigated. The pigments were irradiated with light >630 nm in organic solvents (acetone, tetrahydrofuran, pyridine, methanol, ethanol, n-propanol, 2-propanol and toluene) and in aqueous detergent solutions (cetyl-trimethyl-ammonium bromide [CTAB], lauryldimethyl-aminoxide [LDAO] or sodium dodecyl-sulfate [SDS] and Triton X-100 [TX100]). Their stabilities in these different solvents were determined in the presence and absence of an external sensitizer (pyromethyl-pheophorbide a), oxygen, sodium ascorbate and inert gas (Ar) or vacuum. The photodegradation products of bacteriochlorophyll a in acetone solution were isolated, purified by HPLC and analyzed by their absorption spectra and mass spectroscopy. Besides the well-known dehydrogenation products, such as [3-acetyl]-chlorophyll a, which were obtained as by-products, the major products had low absorption in the visible-near infrared spectral range. The spectral signature of the major component of these products was characteristic of linear open-chain tetrapyrroles, but they lacked the characteristic protonation-deprotonation behavior and reactivity of bilins with Zn(++).     

On-Bead Quantitation of Resin Bound Functional Groups Using Analogue Techniques with Vibrational Spectroscopy

This report introduces two novel methodologies for the on-bead, functional group quantitation of solid phase synthesis using vibrational spectroscopy. "Analogue bleed" quantitation is an infrared spectroscopic technique in which combinatorial library bead spectral data are regressed against solution phase functional analogue spectra of a ligand in question. "Dual Analogue" quantitation is introduced as an infrared or Raman technique in which ligand-to-styrene band ratios of solution phase ligand/styrene monomer standards are used to generate an internally path length referenced calibration which can then be applied to solvent swollen beads. These technologies have application across a wide range of functional groups and can be applied throughout each step of a resin bound synthesis.     

Kinetic modeling of the adsorption rate of a gaseous adsorbate on a granular adsorbent by ultra-rapid-scanning Fourier transform infrared spectrometry

A novel method for determining the rates of adsorption of gaseous adsorbates on granular adsorbents in the millisecond time regime is described. Mixtures of the adsorbate and nitrogen are passed through a solenoid valve and 100 mg of the adsorbent for periods of (typically) 100 ms. The concentration of the adsorbate passing into a low-volume, long path length gas cell is measured with an ultra-rapid-scanning Fourier transform infrared spectrometer capable of gathering 200 mid-infrared spectra per second with 6-cm(-1) resolution. The pressure of the gas entering the cell is measured simultaneously with a capacitance manometer. A dynamic mathematical model was developed to analyze and describe the results in terms of a Langmuir isotherm. The success of this approach is demonstrated by the estimation of the rate of adsorption of vapor-phase acetaldehyde on aminopropylsilylated granular silica gel.     

Infrared spectroscopy of single-walled carbon nanotubes

By using the spectral moments method, we calculate the infrared spectra of chiral and achiral single-walled carbon nanotubes (SWCNTs) of different diameters and lengths. We show that the number of the infrared modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. Furthermore, the dependence of the infrared spectrum as a function of the size of the SWCNT bundle is analyzed. These predictions are useful to interpret the experimental infrared spectra of SWCNTs.     

C80 encaging four different atoms: the synthesis, isolation, and characterizations of ScYErN@C80

The synthesis, isolation, and spectroscopic characterizations of an endohedral fullerene with four heteroatoms encapsulated (ScYErN@C80) are reported for the first time. The isomeric structure and electronic properties of this molecule are studied by various spectrometry methods such as high-performance liquid chromatography (HPLC), laser desorption time-of-flight (LD-TOF) mass spectroscopy, cyclic voltammetry, Fourier transform infrared (FTIR) spectroscopy, and visible-near infrared (vis-NIR) absorption spectroscopy. The carbon cage of ScYErN@C80 is assigned as Ih-C80, and the four-membered ScYErN cluster is suggested to rotate rapidly inside the fullerene cage. Six electrons are transferred from the nuclear cluster ScYErN to the fullerene cage, which leads to a closed-shell electronic structure of the Ih-C80 and results in excellent stability of this molecule.     

微流池多光程土壤有效态氮磷测定方法研究

农业面源氮磷污染是当前地表水体污染主要来源,而土壤有效态氮磷测试大都依赖于流动分析仪在实验室完成,无法满足个性化土壤有效态氮磷现场测定需求。建立了一种微流池多光程的土壤有效态氮磷测定技术,通过柔性化参数设置,实现不同土壤有效态氮磷测试规范和现场测试。以广东省韶关市农业科学研究所和北京市农林科学院提供的26个样品为例进行有效态铵态氮、硝态氮和磷测定验证。实验结果表明,微流池多光程土壤有效态氮磷测定方法中有效态铵态氮、硝态氮和磷的检出限(LOD)分别为0.0086、0.0094和0.0078 mg/L,相对标准偏差(RSD)分别为0.80%、5.7%和0.90%,加标回收率在92.0%~103%,平均单样品测试时间6 min。测试过程自动化,极大地提升了土壤有效态氮磷测定效率和测试结果准确性,为农业面源污染防治提供技术支撑。