基于中红外衰减全反射光谱的氮同位素标记硝态氮的快速测定

采用中红外衰减全反射光谱对溶液和土壤样本中硝态氮含量(14NO3-N/15NO3-N)进行快速测定。结果表明,溶液和土壤样本中硝酸盐的特征吸收区在1200~1500 cm!1,进一步发现,与常规14NO!3相比,15NO!3的吸收峰红移约35 cm!1。在硝酸盐特征吸收区内,干扰吸收少,吸收峰与硝态氮浓度成正比,采用该特征波段的第一主成分与硝态氮含量进行线性回归分析,相关系数R2>0.9840,表明中红外衰减全反射光谱可用于溶液和土壤中硝态氮的快速检测。同时,依据15NO!3吸收峰的红移特征,采用偏最小二乘法对溶液和土壤样本不同氮同位素标记的硝态氮进行建模预测,结果表明,溶液和土壤样本的预测模型均达优秀水平;溶液样本中,14NO3-N和15NO3-N相关系数(R2)均为0.998,有RPD值分别为6.44和4.76;而土壤样本中,14NO3-N和15NO3-N相关系数(R2)分别为0.979和0.968,RPD值分别为5.75和4.78。因此,红外衰减全反射光谱可用于溶液和土壤中硝态氮以及氮同位素标记硝态氮的测定,为快速原位研究土壤中氮的硝化过程提供新的手段。     

铊胁迫水稻的电感耦合等离子体质谱及原位红外光谱分析

采用电感耦合等离子体质谱分析铊胁迫水稻中的Tl、Cr、Co、Ni、Cu、Zn、Mo、Ag、Cd及Pb等重金属元素,并利用原位衰减全反射红外光谱分析了水稻活体叶片的光谱特征。结果表明,铊在水稻叶茎中的含量显著高于谷粒。铊会影响水稻对其它元素吸收,并且在叶与种子中不同元素的吸收积累规律存在差异。水稻叶片的原位衰减全反射红外光谱进一步显示,铊胁迫下叶片的CO2消耗速率明显减少,表明叶片的光合作用受到一定抑制。利用原位衰减全反射红外光谱可直观表现重金属铊对水稻生理过程的胁迫作用。     

FTIR分析在固相有机合成中的应用

综述了近几年来透射、漫反射、衰减全反射、光声及显微红外光谱技术在固相有机合成中的应用研究进展,对它们各自在定性、定量研究固相有机合成中的特点进行了比较.     

傅里叶变换中红外光谱法检测脑胶质瘤

采用傅里叶变换衰减全反射中红外光谱法检测了19例液氮冻存的脑胶质瘤离体组织样品(星形细胞瘤10例, 少枝-星形细胞瘤9例), 对得到的红外光谱进行分析发现, 恶性程度不同的星形细胞瘤组织的红外光谱存在差异, 并且不同类型的脑胶质瘤组织的红外光谱也表现出较为明显的区别, 因此可以根据各个特征吸收峰的峰位、 峰形及谱峰强度等信息来区分脑胶质瘤, 并初步鉴别脑胶质瘤的性质. 研究结果表明, 通过某些特征吸收峰峰位的变化来鉴别星形细胞瘤和少枝-星形细胞瘤与病理诊断结果的符合率约为80%, 说明傅里叶变换衰减全反射中红外光谱法有望发展成为一种对样品无损伤、 快速的脑肿瘤诊断新方法.     

胆囊疾病的临床快速诊断红外光谱新方法研究

研究了衰减全反射(ATR)红外光谱法快速检测胆囊癌的灵敏度和特异性, 结果表明, 正常组织和胆囊癌组织的红外光谱存在一系列差别, 减法光谱技术有助于判别胆囊炎和胆囊癌. 统计分析结果表明, 此方法灵敏度为100%(6/6), 特异性为97%(39/40), 准确率为97%(45/46), 说明中红外ATR光谱法是一种可快速、无创检测胆囊癌组织的新方法.     

单质硫ν_(S-S)伸缩振动的漫反射红外光谱研究

采用傅里叶变换漫反射红外光谱法,在500~400cm~(-1)范围内研究了单质硫S-S键伸缩振动红外吸收模式(νS-S)的一维漫反射红外光谱、二阶导数漫反射红外光谱、四阶导数漫反射红外光谱和去卷积漫反射红外光谱,并针对单质硫νS-S,进一步开展了相关二维漫反射红外光谱研究。结果表明:单质硫νS-S的红外吸收频率主要包括464,466,468,474cm~(-1),而其红外吸收强度的变化顺序为464cm~(-1)474cm~(-1)468cm~(-1)466cm~(-1)。     

HATR-FTIR用于白酒酒精度的测定

采用水平衰减全反射-傅里叶变换红外光谱(HATR-FTIR)法实现了白酒中乙醇含量的快速检测。以1044 cm-1处乙醇的C-OH伸缩振动为特征峰,并通过分峰拟合准确计算其面积,建立了特征峰面积与乙醇浓度之间的标准曲线。幂函数(y=86.017x1.1471,R2=0.9999)的相关性好于线性关系(y=77.492x,R2=0.9903)。方法适合在酒精饮料检测中推广使用。     

傅里叶变换-红外光谱法快速测定面粉中滑石粉

提出了应用衰减全反射(ATR)傅里叶变换-红外光谱(FT-IRS)法快速检测面粉中混入的滑石粉,测定中采用中红外检测器。根据滑石粉的标准红外光谱图并为避免面粉的吸收干扰,选择滑石粉在3 674.96 cm-1及668.16 cm-1两处的特征吸收峰作为判定面粉中是否含有滑石粉的依据,并且其吸收强度随滑石粉含量的增加而增加。由于面粉中滑石粉质量分数低于0.5%和0.2%时,分别在上述两吸收峰波长处已不呈现吸收,方法中将1%(质量分数)作为滑石粉的检出限。此外,根据吸收峰的吸收强度可估算出滑石粉的含量。方法中选用的主要仪器工作条件为:①扫描范围为4 000～650 cm-1;②分辨率为8 cm-1;③扫描信号累加次数为32;④衰减全反射压力常数为100。     

大豆油中掺混地沟油的FTIR定量分析模型

采用红外光谱(FTIR)和偏最小二乘(PLS)法,建立了地沟油掺混比例的衰减全反射(ATR)定量分析模型。分别采集大豆油、地沟油和二者不同掺混比例的红外光谱图,应用TQ化学计量学分析软件,对不同光谱的采集方式,不同化学计量学处理模式进行了比较,并对光谱区域,光谱的预处理方法,主成分因子数进行筛选。依据预测效果确定了最佳的预测模型,其相关系数为0.99,定标均方差(RMSEC)为4.31、预测均方差(RMSEP)为5.55。本法可用于地沟油鉴别的初期检测。     

傅里叶变换红外光谱体表无创探测乳腺肿瘤

利用傅里叶变换红外(FTIR)光谱仪联合衰减全反射(ATR)探头的中红外光导纤维对46名健康志愿者及113名乳腺肿物患者的体表皮肤进行无创红外光谱测定, 并从分子水平比较、分析了正常乳腺和有肿物乳腺体表皮肤的红外光谱特征. 结果表明, 健康志愿者乳房皮肤8个FTIR光谱测定部位的图谱趋于一致; 正常乳腺体表与有肿瘤乳腺体表的吸收峰差异明显, 而1080 cm^-1处核酸相关吸收峰的变化对鉴别肿瘤的良、 恶性有重要意义.     

Advances of sensitive techniques in laser spectroscopy

Different techniques are used for the sensitive detection of overtone transitions of small molecules, such as H₂S, C₂H₂, OCS, O₃ in the visible and near infrared region. The techniques include: phase-modulated or wavelength-modulation absorption spectroscopy with a widely tunable single mode diode laser, opto-acoustic spectroscopy in resonance cells with a color center laser or a Ti:Sapphire laser, and sub-Doppler opto-thermal spectroscopy in cold collimated molecular beams, using a low temperature bolometer as detector. The three techniques are compared with regard to sensitivity and spectral resolution. The mass selective sensitive detection of small metal clusters Li₃ and Na₃ and their high resolution sub-Doppler spectroscopy, using resonant two-photon ionization with cw lasers, is briefly discussed.     

Decongestion of methylene spectra in biological and non-biological systems using picosecond 2DIR spectroscopy measuring electron-vibration–vibration coupling

Methylene is found in the repeat units of many polymers including proteins. In some cases it appears to be a useful reporter of variation in local environment whilst in other contexts average behaviour seems to dominate. In this paper we apply a particular 2DIR technique to a range of systems containing methylene groups, showing that mode frequencies, linewidths and splittings can be easily extracted even when the infrared absorption bands are too congested to allow reliable analysis. 2DIR spectra of polyethylene and several liquid alkanes are compared and it is shown for the case of l-arginine that the methylene scissor modes are split and that this can be resolved by tracking the 2DIR spectrum as a function of time. Calculations from first principles reveal that for most of the methylene modes studied, electrical anharmonicity is the dominant contributor to the 2DIR cross-peak intensity, with the mechanical anharmonicity making only a small contribution.     

Study of the thermal decomposition of a sepiolite by mid- and near-infrared spectroscopies

Near-infrared (NIR) and mid-infrared (MIR) spectroscopies were used to characterize the hydroxyl groups present in a sepiolite and its calcination products at 250, 500 and 800 °C. Calcining the sepiolite at 250 °C was found to result in its dehydration through the loss of coordination water. Raising the calcination temperature to 500 °C caused the sepiolite structure to fold and hydroxyl groups in octahedral layers to be removed. Finally, calcination at 800 °C resulted in a phase change leading to enstatite, as confirmed by XRD spectroscopy.     

Terahertz Time‐Domain Spectroscopy of Gases,Liquids, and Solids

The techniques and methods employed in the spectroscopic characterization of gases, liquids, and solids in the terahertz frequency range are reviewed. Terahertz time‐domain spectroscopy is applied to address a broadband frequency range between 100 GHz and 5 THz with a sub‐10 GHz frequency resolution. The unique spectral absorption features measured can be efficiently used in material identification and sensing. Possibilities and limitations of fundamental and industrial applications are discussed.     

Polarization Dependent Time-Resolved Infrared Spectroscopy and Its Applications

Polarization dependent time-resolved infrared (TRIR) spectroscopy has proven to be a useful technique to study the structural dynamics in a photochemical process. The angular information of transient species is obtainable in this measurement, which makes it a valuable technique for the investigation of electron distribution, molecular structure, and conformational dynamics. In this review, we briefly introduce the principles and applications of polarization dependent TRIR spectroscopy. We mainly focused on the following topics: (i) an overview of TRIR spectroscopy, (ii) principles of TRIR spectroscopy and its advantages compared to the other ultrafast techniques, (iii) examples that use polarization dependent TRIR spectroscopy to probe a variety of chemical and dynamical phenomena including protein conformational dynamics, excited state electron localization, and photoisomerization, (iv) the limitations and prospects of TRIR spectroscopy.     

The Kinetic and Mechanistic Evaluation of NMR Spectra. New analytical methods (18)

In addition to the static parameters of the chemical shifts and coupling constants, which serve as a source of knowledge for molecular structure and stereochemistry, an NMR spectrum can frequently furnish dynamic quantities characterizing relaxation and exchange phenomena. The information about nuclear switching processes has proved to be particularly useful in practice for the detection of internal molecular motions and for the estimation or determination of the corresponding energy barriers. A plethora of studies of this nature has in the past been performed on simple proton spectra. Methodological developments of recent years have led to a significant reduction of the effort required for the quantitative dynamic evaluation of NMR spectra arising from complex spin systems or involving other nuclei. In many cases it has, moreover, become possible to extract detailed mechanistic information inaccessible by other means. The practical execution of such analyses will be explained and illustrated by a selected number of applications.     

Isolation and Spectroscopic Characterization of New Endohedral Fullerenes in the Size Gap of C74 to C76

New alkaline earth metal endohedral fullerenes Sr@C₇₄, Sr@C₇₆‐I, II and Ca@C₇₄, prepared by means of the RF‐method, have been isolated using multistep HPLC. The purity was ascertained by anionic LDI TOF mass spectroscopy, considering the isotopic patterns of the compounds. The influence of the incorporated metal on the electronic structure has been studied by VIS‐NIR and Raman spectroscopy. Photoexcited triplet‐state EPR spectroscopy was used to investigate the structure of these otherwise EPR‐silent fullerenes. Displaying the frequency of the cage vs. encapsulated metal vibrational modes as a function of the square root of the reciprocal masses of the metals clearly separates the M³⁺@C_n^3— and the M²⁺@C_n^2— families. This seems to be a generally applicable tool for monitoring the metal to fullerene charge transfer.