Sites of protonation in phenothiazines: Methane and ammonia chemical ionization mass spectra

Positive ion methane and ammonia chemical ionization mass spectra for ten phenothiazine derivatives are reported. The fragmentations observed in the chemical ionization mass spectra are rationalized in terms of the location of the added proton. High-resolution measurements are used to confirm empirical formulae of the ions in the mass spectra. Changes in the mass spectra with a change in the chemical ionization reagent gas from methane to ammonia are described. A comparison with positive ion secondary ion mass spectra of the same compounds show that the amount of fragmentation is higher in the secondary ion mass spectra, but the same types of ions are observed in spectra produced by both ionization methods.     

有机银溶胶的吸收光谱和表面增强Raman光谱研究

研究了2-氨基苯并咪唑(BIMNH₂)、LiCl、NaOEt对Ag/EtOH溶胶吸收光谱和表面增强Raman散射(SERS)光谱的影响。结果表明,少量的吸附分子BIMNH₂、LiCl、NaOEt均能改变溶胶聚集状态,从而影响其吸收光谱和SERS效应。此外,Cl^-还可与Ag、BIMNH₂形成表面络合物而增强SERS效应。对Ag溶胶体系SERS光谱的溶剂效应也作了初步研究。     

简并谱的涨落统计特征分析

通过引入权重的方式,使简并谱的积累函数形式上连续递增,并用带权重的多元线性拟合提取涨落谱,由此建立一套适用于分析简并谱的NNS分布、谱刚度、能谱分维函数等涨落统计特征的方法,并具体分析了H2O、NH3及CH4分子的振动能谱进行涨落统计特征分析:发现它们的规则谱和约化非简并谱的涨落统计特征均已非Poigson化;而且约化非简并谱的非Poisson化程度较规则谱明显,即前者的能级斥力较后者大;此外,随着简并度的增加,H2O、NH3、CH4的涨落统计特征由非Poisson型向近Poisson型过渡.     

Near-infrared spectroscopy of autunites

NIR spectroscopy has been applied to the study water in the interlayer of the autunite minerals. The spectra of autunites and metaautunites in the first HOH fundamental overtone are different and the spectra of autunites of different origins in the 6000-7500 cm(-1) region are considerably different. A number of conclusions are made based upon the NIR spectra: (a) The spectra of different autunites are different in the NIR spectral region; (b) the spectra of metaautunites show similarity; (c) the spectra of metaautunites are different from that of autunites. NIR spectroscopy provides a method of determination of the structure of water in the interlayer of natural autunites. The implication from the variation in the NIR spectra is that the structural arrangement of water for different autunites is different and is sample dependent. NIR spectroscopy has a wide potential for the study of the autunite minerals.     

Raman-Spektroskopie und Molekülstruktur

Digitized Raman and infrared spectra of 70 steroids are used for the calculation of summarized spectra of all substances with the same structural details. In these spectra bands with low standard deviation are characteristic for the structural detail if they are absent in the other groups of spectra. They can be used for the elucidation of unknown structures.     

Numerical taxonomy and information theory applied to feature selection from filed infrared spectra for automated interpretation

A method is described for the selection of features from infrared spectra, aimed at computer-aided interpretation by retrieval of coded spectra. The coding procedure is similar to that of the ASTM Infrared Spectral Index, involving 140 binary-coded wavelength inter-vals (peak positions) of 0.1 μm for each spectrum (Wyandotte code). In addition to this procedure, windows of 0.3 μm and 0.5 μm are used. For a given set of spectra, the peak positions are grouped by means of numerical taxonomy; the correlation coefficient is used as a criterion. Information contents of all peak positions are calculated with Shannon's formula. One peak position is selected from each group, viz. the position having the highest information content. The selection obtained in this way is composed of peak positions that are weakly correlated yet yield much information. The spectra are then coded again, taking account of the selected peak positions only. In order to evaluate the selection, the number of spectra still differing from all other spectra in the set is determined by comparing all reduced spectra with each other. For a file of 395 spectra (hydrocarbons, alcohols, ethers, carbonyl compounds) 99.0% of the spectra are unique when 27 selected features are used. For a file of 5100 spectra (of a wide variety of compounds, taken from the ASTM Infrared Spectral Index) 97.7% of these spectra are unique when only 40 out of all 140 peak positions are used.     

Comparing similar spectra: From similarity index to spectral contrast angle

We investigated a spectral-contrast-angle (theta) method to determine whether mass spectra of structural isomers are the same or significantly different. This method represents collisionally activated dissociation (CAD) spectra as vectors in space. Mass spectra of different isomers are represented as different vectors, having characteristic lengths and direction. The derived spectral contrast angle, which is a measure of the angle between two vectors corresponding to two closely related spectra, is a measure of whether the mass spectra are the same or significantly different. We compare this method with the similarity index (SI) method and show that the spectral contrast angle method is superior and can differentiate between very similar spectra in cases where the SI cannot. Both methods can be implemented simply in situations where the analyst is called on to decide, on the basis of mass or product-ion spectra, whether reference and unknown compounds are the same or to evaluate the reproducibility of spectra comprised of many peaks.     

用傅里叶变换红外光谱法研究聚对苯二甲酸乙二酯的结构

用傅里叶变换红外光谱法,将一系列不同温度下退火的PET光谱与熔融淬火的PET光谱进行数字吸光度相减,得到不同结晶状态的“反式构象光谱”。进一步将不同温度退火的“反式构象光谱”(240℃和120℃)彼此相减,可得到“纯晶区的光谱”和“非晶区的反式构象光谱”。通过差示光谱的比较,发现一些新的谱带和谱带的变化。可用PET 的晶区和非晶区中其分子链的内旋转构象的变化解释。     

Valenzbandspektroskopie mit der Mikrosonde

The special properties of X-ray valence-band spectra in comparison with inner-orbital spectra are described and relations between the fine structure of valence-band spectra and parameters characteristic for the electronic structure of a sample are shown. Proceeding from these connections the new possibilities are presented for obtaining analytical information by evaluation of the structure parameters of valence-band spectra, using the example of the extension of electron-microprobe analysis.     

Use of fast atom bombardment mass spectrometry for the characterization of nitroaromatic isomers

Positive and negative ion fast atom bombardment (FAB) mass spectra of some monosubstituted nitroaromatic isomers are reported. Generally ions carresponding to [M + H]⁺ and M⁺ are observed in the positive ion FAB spectra; ions such as [M ? H] ^? and M^?˙ are observed in the negative ion FAB spectra. The use of FAB mass spectra to distinguish the isomers is discussed. Comparisons of FAB, chemical ionization and electron impact mass spectra of the same isomers (wherever possible) are reported. The structural information obtained in the negative ion FAB spectra complement those obtained in the positive ion FAB spectra.     

Differentiation of diastereomeric conduramine derivatives under electron ionization and chemical ionization mass spectral conditions

Diastereomeric conduramine derivatives, i.e., (1R,2S,3R/S,6S)-6-(N-carbomethoxyamino) 1,2-O-isopropylidenecyclohex-4-ene-1,2,3-triol (1 and 2) and their O-acetyl derivatives (3 and 4), were studied using gas chromatography (GC) with electron ionization (EI) and chemical ionization (CI). The EI mass spectra of diastereomeric pairs show consistent differences in the relative abundances of characteristic ions. The EI fragmentation patterns are based on precursor/product ion spectra, high-resolution mass spectrometry (HRMS) and deuterium labelling. The CI spectra show differences from the EI spectra, and the isobutane/CI spectra are much simpler than the methane/CI spectra. The differences shown in the CI spectra are similar to those shown in the product ion spectra of [M+H](+) ions generated under electrospray ionization (ESI) conditions. Theoretical calculations are performed to understand the observed differences. The differences in the relative stabilities of molecular ions, or protonated molecules at different sites, can explain the observed differences in the spectra.     

CH-stretching overtone spectra of cis- and trans-1,3-pentadiene

The room-temperature vapor-phase overtone spectra of cis- and trans-1,3-pentadiene (piperylene) have been recorded in the 5000-17500 cm(-1) region with the use of conventional and intracavity laser photoacoustic spectroscopy. The presence of five nonequivalent olefinic CH bonds and one methyl group in each molecule complicates assignment of the spectra. We have used a harmonically coupled anharmonic oscillator local mode model with one oscillator for each of the nonequivalent CH bonds to calculate the CH-stretching overtone spectra and thus facilitate assignment of the spectra. Our calculated spectra are in good agreement with the observed spectra. The observed high overtone spectra are distinctively different despite the similarity of the two molecules and the numerous and broad transitions.     

A spectral similarity measure using Bayesian statistics

A spectral similarity measure was developed that can differentiate subtle differences between two spectra. The spectra are digitalized into a vector. The difference between the two spectra is defined by a difference vector, which is one spectrum minus the other. The spectral similarity measure is transformed into a hypothesis test of the similarities and differences between the two spectra. The scalar mean of the difference vector is used as the statistical variable for the hypothesis test. A threshold for the hypothesis that the spectra are different was proposed. The Bayesian prior odds ratio was estimated from multiple spectra of the same sample. The posterior odds ratio was used to quantity the spectral similarity measure of the two spectra. Diffuse reflectance near-infrared spectra of tobacco samples of two formulations were used to demonstrate this method. The results show that this new method can detect subtle differences between the spectra.     

顺,反式环丙烷衍生物异构体的区分

在化学电离条件下，研究了４种顺、反式环丙烷衍生物与丙酮和醋酸乙烯酸乙烯酯的分子离子反应。异构体１，２的丙酮ＣＩ谱及其加合离子「Ｍ＋Ｈ＋Ａ」的ＣＩＤ谱都 可以区分该对异构体。化合物２，３和４可以和质子化丙酮及质子化二聚体发生加合反应，但化合物１仅能与质子化丙酮发生加合反应。在醋酸乙烯酯的ＣＩ谱中，观察到４个化合物的质子化二聚体，其中异构体１，２的质子化二聚体的ＣＩＤ谱也能反映它们立体结构的差异。     

Identification de composes inconnus en spectrometrie de masse par Comparaison a une Bibliotheque sur Cartouches Digitales

An automatic method for interpretation of mass spectra is described. This approach uses the comparison of unknown spectra with those included in a library of standard references. The spectra are stored on digital magnetic tape. Several hundred spectra can be recorded on a cartridge. The tape unit is connected to a minicomputer. This system offers many advantages and is very well suited for medium sized laboratories. The series of compounds studied are the olefins, compounds with very similar spectra, so the method of interpretation has to be powerful. The different parts of the identification algorithm are discussed. The results and experimentation are also presented.     

Spectral variations in background light emission of surface-enhanced resonance hyper Raman scattering coupled with plasma resonance of individual silver nanoaggregates

We demonstrate the origin of spectral variations in background light emission of surface enhanced resonance hyper Raman scattering (SERHRS) from single Ag nanoaggregates. Ag nanoaggregate-by-nanoaggregate variations in background light emission spectra are related to plasma (plasmon) resonance spectra. Temporal variations in background light emission spectra with temporal blueshifts in plasma resonance spectra are also observed under continuous laser excitation. Both types of the variations in background light emission are reproduced by multiplying background light emission spectra measured from a Ag microaggregate by Lorentz function spectra derived from plasma resonance spectra. The reproduction reveals that second electromagnetic (EM) enhancement by plasma resonance is the origin of the variations. Additionally, spectral variations in background light emission of SERHRS are similar to that of surface enhanced resonance Raman scattering (SERRS). The similarity indicates that both types of background light emission commonly obtain second EM enhancement from identical plasma resonance.     

Angle-resolved metastable fragment yields spectra of N2 and CO in K-edge excitation energy region

Angle-resolved metastable fragments yields spectra have been measured in the N 1s ionization region of the N(2) and C 1s ionization region of CO. These spectra are compared with zero kinetic energy electron and photoelectron spectra. It has been shown that an isotropic metastable fragments yields spectra are almost identical with the ZEKE spectrum, whereas metastable fragments yields spectra with the Σ-Σ transition show similarity with photoelectron spectra. This means that these spectra clearly contain information about two shake-up mechanisms: conjugate and direct shake-up processes. All the peaks in the metastable photofragment spectra can be assigned as either satellite states or double/triple excitation states. Thus, it was shown that angle-resolved metastable photofragment spectroscopy could be used to help characterize multi-electron excitation states in general.     

Calculation of IR spectra of the elementoorganic dendrimers

Various approximations to the analysis of the dendrimer vibrational spectra are introduced. The merits and demerits of the fragment method, calculation of the first generation and linear chains containing different number of the repeated units are discussed. The experimental spectra of two series of the phosphorus-containing starburst dendrimer generations are interpreted on the basis of the calculation of the frequencies of the normal vibrations and the band intensities in their IR spectra. The analysis of spectra enables one to assign the characteristic bands for the groups in the core, in the repeating unit and the terminal groups of the dendrimers. This assignment is supported by the calculation of the absorption curves with the force constants and electro-optical parameters (EOP). The vibrational spectra of studied starburst dendrimers (SD) (up to 11 generations) are in general identical to begin with four generation. The most marked changes of band position and their intensities are seen in spectra of the first generations, when all fragments of molecule contribute appreciably to the spectral pattern. The comparative study of vibrational spectra of SD and linear polymers reveal their main characteristic features, which are determined by their structural peculiarities.     

5,10,15,20-四(对-十四酰亚胺基苯基)卟啉及其锰、锌配合物的合成及性质

合成了5,10,15,20-四(对-十四酰亚胺基苯基)卟啉配体(TMPPH2)及其锰、锌金属配合物(TMPPMnCl, TMPPZn), 并通过紫外-可见光谱、红外光谱、核磁共振氢谱、元素分析等技术对化合物的结构加以确认, 研究了配体和配合物的拉曼光谱、光电子能谱和荧光光谱的变化及电化学性质. 结果表明, 配体和配合物的紫外光谱、红外光谱、拉曼光谱、荧光光谱及光电子能谱都有很大区别, 锰配合物的循环伏安曲线与配体和锌配合物不同, 除了卟啉环发生氧化还原外, 还发生了金属离子的氧化还原反应.     

Software algorithm for automatic interpretation of mass spectra of glycerolipids

A new software algorithm for automatic interpretation of mass spectra of glycerolipids has been developed. The algorithm utilizes a user-specified list of parameters needed to process the spectra. The compounds in mass spectra are identified according to range of measured m/z values, after which the spectra are automatically corrected by the content of naturally occurring isotopes and ion intensities of identified compounds by response correction factors. Automatic processing of the spectra was shown to be accurate and reliable by testing with numerous spectra of glycerophospholipids obtained by liquid chromatography/electrospray ionization mass spectrometry and by comparing the results with manual interpretation of the spectra. If quantitative analysis using internal standards is performed, all the identified compounds in the sample are quantified automatically. A dilution factor may be defined for each sample and is applied to correct the alterations in sample concentration during sample preparation. Processing of several replicate spectra simultaneously produces mean results with standard deviations. The software may also be used to subtract the results of two analyses and to calculate the mean result of replicate subtractions. The algorithm was shown to save time and labor in repetitive processing of mass spectra of similar type. It may be applied to processing of spectra obtained by various mass spectrometric methods.