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.     

尿微量白蛋白的多波段多光程光谱检测

为研究多光程光谱法检测尿微量白蛋白含量的可行性,利用多光程光谱的非线性特性,设计自动微位移测量装置,实现对尿液样品可见波段和近红外波段的多光程(0～4.0 mm)光谱快速采集.采用偏最小二乘法,分别对样本的可见波段、近红外波段、可见-近红外双波段的多光程吸收谱与尿液中白蛋白实际含量建立回归模型,其中,可见-近红外双波段...     

近红外光谱与化学计量学方法用于镉污染稻米的定性鉴别

采用近红外光谱漫反射模式结合化学计量学方法对稻米镉含量是否超标进行可行性鉴别分析.本研究收集了120个样本,测定其镉含量值(合格49个,不合格71个).对光谱数据预处理方法优化,确定了平滑,一阶导数以及自归一化后的数据作为输入变量.采用竞争性自适应重加权算法筛选了45个关键变量,并对上述变量的光谱吸收带进行归属.比较了主成分分析-判别分析法、偏最小二乘识别分析、线性判别分析、K-最近邻法与簇类独立软模式法5种模式识别方法.确定采用偏最小二乘识别分析建模效果最好,模型训练集与预测集鉴别准确率分别达到98.8％与91.7％.结果表明,近红外光谱作为初筛方法可用于鉴别稻米中镉含量是否超标.     

基于组合偏最小二乘的特征波段优选方法在氨、碱化处理玉米秸秆粗蛋白检测中的研究

该文构建了玉米秸秆粗蛋白定量分析模型,并对光谱特征波段选取方法进行探讨及验证。首先对107个样本进行预处理,剔除两个异常样本后采用DB2小波缺省阈值4层分解方式进行光谱重构,预处理后粗蛋白模型交互验证决定系数R2CV从0.788 9提高至0.920 8,采用间隔偏最小二乘(IPLS)及其改进型方法后向区间间隔偏最小二乘(BIPLS)、组合间隔偏最小二乘(SIPLS)进行特征波段选取,并对比主成分分析、竞争性自适应重加权采样法、相关系数法、遗传算法、移动窗口最小二乘等结果,发现基于IPLS及其改进型BIPLS、SIPLS均可有效、准确定位特征波段区间,其中采用SIPLS 30 波段间隔在10 128~10 398 cm-1与11 196~11 462 cm-1时具有最优模型,验证集相关系数(rp)为0.978 4,验正集决定系数(R2P)为0.957 2,验正集均方误差根(RMSEP)为0.221 1,相比于其他波段选取方法表现出较好的实时准确性,该方法可为玉米秸秆氨碱化最优条件判定提供重要的数据支撑。     

激光诱导击穿光谱结合CARS变量选择方法定量检测奶粉中的镁

为监测奶粉中的镁(Mg)元素含量,本研究利用激光诱导击穿光谱(LIBS)技术对奶粉中Mg元素进行定量检测。对于每个样品,采用压片机在20 MPa压力下进行压片处理,然后利用高精度光谱仪在200~750 nm波段范围内获取压片样品的LIBS光谱。根据LIBS光谱特征,将光谱划分为4个波段,并进行初步的波段优选和光谱预处理分析。在此基础上,采用竞争性自适应重加权算法(CARS)对波长变量进行优选,再应用偏最小二乘法(PLS)建立奶粉中Mg元素含量的预测模型,并对预测集样本进行预测。研究结果表明,LIBS技术结合CARS变量选择方法可以用于奶粉中Mg元素含量的定量检测,最优CARS-PLS预测模型的校正集和预测集的决定系数及平均相对误差分别为0.9999,0.20%和0.9742,3.29%,优于原始光谱所建立的PLS模型,且所用波长变量仅为PLS模型的7.7%。由此表明,CARS方法能有效选择有用的波长变量,可简化预测模型及提高预测模型的稳定性。本研究为奶粉中镁元素含量的快速定量分析提供参考。     

傅里叶变换红外光谱结合模式识别法快速鉴别食用油的真伪

采用傅里叶变换红外光谱(FTIR)结合簇类独立软模式识别技术(SIMCA)建立了真伪食用油的快速鉴别方法.该方法依据FTIR的指纹特性,收集并分析了53个合格食用油和13个伪造食用油的FTIR谱图;通过对谱图取二阶导数和标准化处理,主成分分析(PCA)提取特征变量;采用SIMCA方法分别随机选取43个合格食用油和9个伪食用油样品的FTIR谱图组成训练集,构建得到真伪食用油的SIMCA分类模型.该模型经过剩余10个合格食用油和4个伪食用油的验证,正确识别率达到了100%.说明FTIR结合SIMCA可能成为快速鉴别食用油真伪的一种新方法.     

便携式近红外光谱仪对废旧涤/棉混纺织物中涤含量的快速检测

利用近红外光谱技术对252个涤/棉混纺织物进行研究,建立了不同光谱特征的涤/棉混纺织物的偏最小二乘(PLS)定量分析模型。将近红外光谱异常样本与光谱正常样本分别建模,显著提高了定量分析模型的预测精度、拓宽了模型的适用范围。以涤、棉主要吸收峰区间为基本建模波段,进行双向扩展,筛选出最佳建模波段,以相关系数(R)、预测集标准差(SEP)和验证集准确率优化建模条件,并与未分别建模的PLS模型相比较。用346个未参与建模的废旧涤/棉混纺织物对模型进行外部验证,外部验证准确率为92%,识别时间8s。     

基于拉曼光谱成像的食品中化学添加剂的无损检测

基于拉曼光谱成像技术对小麦粉中过氧化苯甲酰和L-抗坏血酸进行快速、无损、原位检测,并对2种添加剂的空间分布进行了可视化研究.采用实验室自行搭建的线扫描式拉曼光谱成像系统,激发光源波长为785 nm,有效光谱范围为0~2885.7 cm~(-1).分别在小麦粉中添加含量为0.1%~30%的过氧化苯甲酰和L-抗坏血酸,对制备的样品进行拉曼光谱扫描,选取感兴趣区域的光谱信号进行平均,得到平均光谱代表该样品的拉曼信息.分别选取过氧化苯甲酰和L-抗坏血酸的2个特征峰,与该物质在小麦粉中的含量建立线性关系,其决定系数R~2分别为0.9828和0.9912.采集的特征波段拉曼图像经过自适应迭代重加权惩罚最小二乘(air PLS)方法扣除荧光背景后,选取合适的特征峰强度作为阈值,对校正拉曼图像进行二值化分析,得到添加物的空间分布可视化图像.该方法与点检测拉曼技术相比,具有检测结果准确且检测时间较短的优势,且可以实现不均匀样品中多种物质的同时检测与分布可视化.     

公共安全视域下精神药物光谱学无损分类

该文对苯二氮类和吩噻嗪类镇静安眠药样品的红外光谱数据进行采集,构建了不同数据分类模型并对比了不同波段光谱数据集对其分析准确率的影响.结果表明,借助贝叶斯判别分析的基于全波段数据集的二阶导数模型分类效果优于其他单一模型,对于苯二氮类和吩噻嗪类两个不同类型精神药物的总体分类准确率达92.7％.借助贝叶斯判别分析的基于全波段和指纹区融合数据集的二阶导数融合模型分类效果最佳,对苯二氮类和吩噻嗪类两个不同类型精神药物的总体分类准确率达到100％;对苯二氮类和吩噻嗪类中不同种类精神药物的总体分类准确率则分别达到96.7％和100％.该研究实现了不同类型及同一类型不同种类镇静安眠药的快速准确定性分析,为此类管制类药物走私案件的准确定性提供了一定的技术支持.     

ZnO纳米管的光学性质及其对甲基橙降解的光催化活性

以十二烷基硫酸钠为模板剂采用水热法合成了ZnO纳米管,以尿素和ZnSO4为原料制备了ZnO纳米颗粒,并应用透射电镜、x射线衍射、光致发射光谱、拉曼光谱、比表面积测定、傅里叶红外光谱和紫外-可见漫反射光谱等技术对样品进行了表征.结果表明,ZnO纳米管的比表面积较大,在λ≈650nm的可见光波段ZnO纳米管开始出现吸收峰,而ZnO纳米颗粒在可见光波段几乎没有吸收.ZnO纳米管和纳米颗粒在紫外光照射下均对甲基橙有降解作用,其中ZnO纳米管的光催化活性较高.随着催化剂用量的增加和光照时间的延长,甲基橙降解率逐渐提高;甲基橙浓度的增大使甲基橙降解率降低.     

气相CBr2的激光诱导荧光光谱

本文报道了在交叉分子束装置中氟原子和二溴甲烷反应生成的CBr2的气相激光诱导荧光光谱的首次实验结果。位于585-664nm范围内的激光诱导荧光光谱由22个峰组成,被指定为CBr2的A(V1'V2'0)←X(000)(V1'=0,1; V2'=0-12)跃迁。从光谱导出v00=14885cm^-^1, 上态振动光谱常数v1'=460, v2'=189cm^-^1, x12'=3.10,x22'=-0.27cm^-^1。本实验结果与CBr2的低温固相光谱进行比较, 发现固相光谱较气相光谱明显蓝移, 确认了CBr2是F+CH2Br2过程的两步反应的产物。     

Vibronic spectra of the allyl radical at 6-8 eV with resonance-enhanced multiphoton ionization technique

The allyl radical was produced in molecular beam by pyrolysis of allyl iodide. The vi-bronic spectra from ground state to six new electronic states of the allyl radical at 6-8 eV, π→3dxz, π→3dxy, and π→ns (n=4, 6, 7, 8) were observed firstly with the aid of time-of-flight mass spectros-copy and resonance-enhanced multiphoton ionization technique. Vibrational progression of v7 (C3 bend) with gross spacing of about 430 cm-1 was observed in ns Rydberg states. The adiabatic ionization potential of the allyl radical was obtained to be (65641 ± 20) cm-1 ((8.138± 0.002) eV) by fitting the term values of ns (n=4,6,7,8) Rydberg states with Rydberg formula.     

CF2自由基A态伸缩振动频率的测定

Laser induced fluorescence excitation spectroscopy has been used to determine the previously ambiguous assignments of A-state stretching frequencies of CF2 radical under supersonic free jet conditions. The measured frequencies are v’1=1012.1±0.5cm-1, v’3=1180.2±0.5cm-1, which is in good agreement with Cameron's[6] calculation result. Furthermore, some transitions attributed to the (1,n-2,0)←(0,0,0), n≦6 progressions are first reported, and new parameters are derived from the spectra obtained.     

Tunneling splittings for "O...O stretching" and other vibrations of tropolone isotopomers observed in the infrared spectrum below 800 cm(-1)

Fourier transform infrared absorption spectra containing evidence for about two dozen spectral tunneling doublets are reported for gaseous tropolone(OH), tropolone (OD), and 18O,18O-tropolone(OH) in the 800 to 300 cm-1 spectral range. No FTIR absorption was detected in the 300-150 cm-1 range. The known zero-point (ZP) tunneling splitting values Delta0 = 0.974 cm-1 for tropolone(OH) (Tanaka et al.) and 0.051 cm-1 for tropolone(OD) (Keske et al.) allow vibrational state-specific tunneling splittings Deltav to be estimated for fundamentals including three with strong O...O stretching displacements [cf. for tropolone(OH) nu13(a1) = 435.22 cm-1 with HDelta13 = 1.71 cm-1 = 1.76 HDelta0, and for tropolone(OD) nu13(a1) = 429.65 cm-1 with DDelta13 = 0.32 cm-1 = 6.27 DDelta0]. The majority of Deltav splittings in the sub-800 cm-1 range are dilated relative to the isotopomer Delta0 values. The FTIR spectra demonstrate the presence of dynamic couplings and potential function anharmonicity in addition to revealing Deltav splittings and many OH/D and 18O/16O isotope effects. Approximate values are obtained for the ZP splittings 88Delta0 and 86Delta0 of the doubly and singly 18O-labeled isotopomers of tropolone(OH). The diverse values of the observed Deltav/Delta0 splitting ratios underscore the inherent multidimensionality and corner-cutting activities entering the state-specific tunneling processes of the tropolone tautomerization reaction.     

IR photodissociation spectroscopy and theory of Au+(CO)n complexes: nonclassical carbonyls in the gas phase

Au+(CO)n complexes are produced in the gas phase via pulsed laser vaporization, expanded in a supersonic jet, and detected with a reflectron time-of-flight mass spectrometer. Complexes up to n = 12 are observed, with mass channels corresponding to the n = 2 and n = 4 showing enhanced intensity. To investigate coordination and structure, individual complexes are mass-selected and probed with infrared photodissociation spectroscopy. Spectra in the carbonyl stretching region are measured for the n = 3-7 species, but no photodissociation is observed for n = 1, 2 due to the strong metal cation-ligand binding. The carbonyl stretch in these systems is blue-shifted 50-100 cm-1 with respect to the free CO vibration (2143 cm-1), providing evidence that these species are so-called "nonclassical" metal carbonyls. Theory at the MP2 and CCSD(T) levels provides structures for these complexes and predicted spectra to compare to the experiment. Excellent agreement is obtained between experiment and theory, establishing that the n = 3 complex is trigonal planar and the n = 4 complex is tetrahedral.     

Noble gas-actinide compounds: evidence for the formation of distinct CUO(Ar)(4-n)(Xe)(n) and CUO(Ar)(4-n)(Kr)(n) (n = 1, 2, 3, 4) complexes

Laser-ablated U atoms react with CO in excess argon to produce CUO, which gives rise to 852.5 and 804.3 cm-1 infrared absorptions for the triplet state CUO(Ar)n complex in solid argon at 7 K. Relativistic density functional calculations show that the CUO(Ar) complex is stable and that up to four or five argon atoms can complex to CUO. When 1-3% Xe is added to the argon/CO reagent mixture, strong absorptions appear at 848.0 and 801.3 cm-1 and dominate new four-band progressions, which increase on annealing to 35-50 K as Xe replaces Ar in the intimate coordination sphere. Analogous spectra are obtained with 1-2% Kr added. This work provides evidence for eight distinct CUO(Ng)n(Ar)4-n (Ng = Kr, Xe, n = 1, 2, 3, 4) complexes and the first characterization of neutral complexes involving four noble-gas atoms on one metal center.     

Structural characterization of molybdenum(V) species in aqueous HCl solutions

Mo(V) aqua-chloro complexes in hydrochloric acid solutions have been studied by means of Mo K- and L2,3-edge X-ray absorption and Raman spectroscopic methods. The solid compounds (HPPh3)2[MoOCl5] (1), 6[MoOCl4(H2O)]-.10(pyH)+.4Cl- (2), and (pyH)2[Mo2O4Cl4(trans-OH2)2] (3) were used for structural comparisons. The compound 2 crystallizes in the orthorhombic space group Pmma (no. 51) with a=21.398(3), b=8.057(4), c=13.330(4) A, and Z=4. In 0.2 M solutions of MoCl5 in 7.4-9.4 M HCl the mononuclear [MoOCl4(OH2)]- complex dominates with the bond distances Mo=O 1.66(2) A, Mo-Cl 2.38(2) A, and Mo-OH2 2.30(2) A. Its Raman band at 994 cm-1 for the Mo=O symmetric stretching vibration is closer to that of 2 (988 cm-1) than of 1 (969 cm-1). The Mo K-edge EXAFS spectrum for 0.2 M MoCl5 in 1.7 M HCl solution reveals a dinuclear [Mo2O4Cl6-n(OH2)n]n-4 (n=2, 3) complex with a double oxygen bridge and the average distances Mo=O 1.67(2) A, Mo-(mu-O) 1.93(2) A, Mo-Cl 2.47(3) A, Mo-Mo 2.56(2) A, and a short Mo-OH2 distance of 2.15(2) A, which implies that at least one of the aqua ligands is in equatorial position relative to the two axial Mo=O bonds. This position differs from the Mo-OH2 configuration exclusively trans to the M=O groups of the isomeric (with n=2) dinuclear complex in 3. The difference in the ligand field is also reflected in their L2,3-edge XANES spectra. For 0.2 M MoCl5 solutions in intermediate HCl concentrations (3.7-6.3 M) the Raman bands at 802 cm-1 (Mo-O-Mo) and 738 cm-1 (Mo-(mu-O)2-Mo) verify three coexisting classes of Mo(V) complexes: mononuclear complexes together with dinuclear mono-oxo (e.g., [Mo2O3Cl6(H2O)2]2-) and dioxo bridged species, even though principal component analysis (PCA) of the corresponding series of EXAFS spectra only could distinguish two major components. By fitting linear combinations of the appropriate EXAFS oscillation components, dioxo-bridged dinuclear complexes were found to dominate at HCl concentrations相似文献   

A Fourier transform infrared spectroscopic study of Mg-rich, Mg-poor and acid leached palygorskites

The FTIR spectra of pure magnesium-rich (Mg-rich) and magnesium-poor (Mg-poor) palygorskites, before and after short-term (<7 h) and long-term (360 h) acid leaching are presented here. Comparison of decomposition spectra of Mg-rich and Mg-poor palygorskites clearly shows that the absorption peaks related to pairs of octahedral cation differ depending on the octahedral site occupancy. Short-term acid leaching of palygorskites results in significant changes to FTIR absorption bands near 1200 and 790 cm-1. As the acid attack progresses, the band at 1200 cm-1 shifts to lower wavenumbers, whilst the band at 790 cm-1, which here is assigned to SiU-O-SiD symmetrical stretching vibration, shifts to higher wavelengths. Longer-term leaching of palygorskites results in the disappearance of 900-1200 cm-1 absorption bands, showing that the palygorskite has largely decomposed to amorphous silica. Assignments of several other bands have been made as follows: several vibrations relate to OH, i.e. 847 cm-1, hygroscopic water (1635 cm-1), Si-O vibrations 1100, 611-621, 470-481 cm-1, etc. appear in the FTIR spectra of 360 h acid leached palygorskite. Three bands near 1100, 611-621 and 470-481 cm-1 relate to Si-O vibration of an ideal hexagonal (Si2O5)n sheet.     

Eu3+,Tb3+混配配合物的激光诱导荧光

利用激光诱导荧光技术研究了两种三价稀土金属离子的β－二酮与有机配体混配络合物中金属离子的寿命及其能级结构，得到了Ｅｕ＾３＋的能级常数。     

稀土元素与L-酪氨酸和甘氨酸三元固态配合物的合成及表征

目前稀土与氨基酸三元固态配合物的研究着重于少数稀土-氨基酸-非氨基酸类型.本文报道了10种稀土与L-酪氨酸(Tyr,HO——CH_2(NH_2)CHCOOH)和甘氨酸(Gly,NH_2CH_2COOH)三元固态配合物的合成及FTIR光谱、质谱表征.