Descriptive,interactive computer-assisted interpretation of infrared spectra

A knowledge-based system for interpreting infrared spectra which explains the rationale behind the interpretation process, in a step-by-step fashion, has been developed. The user, having been informed of the basis for decisions made during interpretation of the data, is better able to understand, and thereby to utilize, the results. Additional features allow the informed user to participate in the interpretation of the spectral data, thereby increasing the quality and quantity of data available to the system. In addition to assisting researchers, this system can be used for computer- assisted instruction of the infrared spectral interpretation process.     

Identification of some polyatomic inorganic anions as their diphenyliodonium salts by infrared spectroscopy and interpretation of the spectra

The main features of infrared spectra of the diphenyliodonium salts of some polyatomic anions are reported and interpreted, and their application in qualitative analysis discussed.     

Use of an Infrared Laser in a Detection System for Liquid Chromatography

Abstract

A liquid chromatography detection system based on an infrared laser has been constructed and some tentative evaluations of its performance have been made. Although restricted to use with a very few solvents (mainly halocarbons), this system should be applicable whenever chloroform or a halocarbon solvent of lower strength (polarity) can be used. Injected sample quantities as small as one microgram have been detected on elution.     

Lithium hydroxide phase transition under high pressure: an ab initio molecular dynamics study.

The high-pressure phase transition in the deuterated lithium hydroxide crystalline state has been studied by Car-Parrinello molecular dynamics simulations, in the constant-pressure, constant-temperature ensemble. The recently developed metadynamics approach has been applied to encourage the system to transform into different phases in an affordable simulation time. A previously not completely characterized high-pressure phase has been obtained. The structural and spectroscopic properties have been studied and compared with the neutron scattering, infrared and Raman measurements. It has been found that the calculated structure differs slightly from the experimental hypothesis, and that the presence of strong hydrogen bonds is the source of the red shift and of the characteristic features of the OD-stretching bands in both IR and Raman spectra.     

A window fourier domain search system

A search system is presented that utilizes Fourier domain data. This system removes dominating features from the infrared absorbance data, transforms the data into the Fourier domain and performs a complete library search. The actual matching algorithm is very simple and excellent search results were attained using 16 cm^–1 resolution infrared absorbance spectra before transformation. This method can be used to distinguish very similar spectra that cannot be distinguished by many other search methods.     

Investigating the feasibility of mid infrared spectroscopy for monitoring an industrial de-racemization biotransformation process

Biotransformation processes have become industrially important in recent years as routes to the manufacture of high value chemical intermediates. However, measurements of key process features and analyte concentrations during these processes are still typically carried out using off-line analysis methods. Vibrational spectroscopic techniques have been extensively utilised for the monitoring and control of a variety of industrial processes. Despite the techniques success with a range of challenging biological matrices, including fermentation and cell culture systems, application of this approach to biotransformation systems has been limited. In the present study the potential of mid infrared spectroscopy to monitor an industrially relevant de-racemization biotransformation process has been investigated. This process presents a number of difficulties due to the optically challenging sample media, close structural similarities and stoichiometric relationship between the key analytes of interest. A PLS model based on the mid infrared spectra obtained during three replicates of the biotransformation process was constructed. In order to ensure that co-linearity within the system had been adequately addressed the spectral contributors to the model were examined. External validation of the constructed model was achieved by challenging the model with two previously unseen replicates of the process. The constructed model was able to predict the concentrations of two key analytes in various samples from these unseen replicates without the requirement for any time consuming sample pre-treatment stages, thus demonstrating the feasibility of near real-time mid infrared monitoring of such an industrial de-racemization biotransformation process.     

Fatty Acids and Their Metal Salts: A Review of Their Infrared Spectra in Light of Their Presence in Cultural Heritage

In a cultural heritage context, fatty acids are usually found as breakdown products of lipid-containing organic remains in archaeological findings, binders in aged oil paintings, and additives in modern art-related materials. They may further interact with the ionic environment transforming into metal soaps, a process that has been recognized as a threat in aged paintings but has received less attention in archaeological objects. The investigation of the above related categories of materials with infrared spectroscopy can provide an overall picture of the organic components’ identity and demonstrate their condition and prehistory. The capability of investigating and distinguishing fatty acids and their metal soaps through their rich infrared features, such as the acidic carbonyl, the carboxylate shifts, the variable splits of alkyl chain stretching, bending, twisting, wagging, and rocking vibrations, as well as the hydroxyl peak envelopes and acid dimer bands, allows for their direct detailed characterization. This paper reviews the infrared spectra of selected saturated fatty monoacids and diacids, and their corresponding sodium, calcium, and zinc salts and, supported by newly recorded data, highlights the significance of their spectroscopic features.     

Expertise — an expert system for infrared spectra evaluation

A system for the automated elucidation of chemical structures by the interpretation of infrared spectra is described. “Rules” for the finding of substructure features in an unknown spectrum are obtained by a pattern recognition procedure. A structure generation algorithm links particular substructures, called “superatoms”, together. Fuzzy set operators are used to consider inaccuracies in peak positions and intensities.     

Microimaging FT-IR of head and neck tumors. V. Odontogenic cystic lesions

This study has been undertaken to investigate spectral features of cystic lesions of the jaw with the aim to understand their tumoral progression and to evidence initial signals of neoplastic changes.Three important groups (according to the World Health Organization classification) representing inflammatory (radicular) and developmental (orthokeratinized odontogenic, OOC) cysts as well as keratocystic odontogenic tumor (KCOT) of the jaw have been studied by microimaging infrared spectroscopy. From the spectral data analysed with the multivariate pattern recognition procedure, representative spectra were isolated and used to build correlation maps to localize the biochemical components in the tissue.The procedure enabled to better understand spectral features of these classes of cysts and to discriminate tumoral from non-tumoral spectra through the analysis of ‘vibrational markers’. In KCOT, the correlation of calcium derivatives (in metaplastic or displastic bones) with the tumor has been highlighted, too. The distribution of various biochemical components in the tissues, achieved through correlation maps of representative spectra, resulted in satisfactory agreement with the histopathological analysis. ‘Spectral isolation’ of micro tumorigenic zones in some normal OOC cysts, demonstrated the potentiality of infrared spectroscopy to evidence the early stage of a hidden lesion.     

Rotational dynamics of CO solvated in small He clusters: a quantum Monte Carlo study

The rotational dynamics of CO single molecules solvated in small He clusters (CO @ HeN) has been studied using reptation quantum Monte Carlo simulations for cluster sizes up to N = 30. Our results are in good agreement with the rotovibrational features of the infrared spectrum recently determined for this system and provide a deep insight into the relation between the structure of the cluster and its dynamics. Simulations for large N also provide a prediction of the effective moment of inertia of CO in the He nanodroplet regime, which has not been measured so far.     

Infrared study of 1-octanol liquid structure

A detailed analysis of the temperature behavior of the OH stretching bands in infrared (IR) and near infrared (NIR) spectra has been performed for neat liquid 1-octanol. Spectral features have been interpreted using a three-state model, based on different typologies of OH oscillator. The H-bond energy dispersion has been calculated from IR data. Structural properties such as self-association degrees and H-bonding enthalpy formations have been reported. Results have been compared with recent Molecular Dynamic simulation studies. From temperature induced intensity variations the average H-bonding cooperative energy is evaluated. For the 1-octanol liquid system a break point temperature is detected around 50 °C. The existence of two temperature domains connected with self-association properties is in agreement with the behavior of relaxation processes evidenced in previous light scattering studies. These results evidence the correlation existing among structural and dynamical properties in complex self-associating liquid systems.     

Proton dynamics in the strong chelate hydrogen bond of crystalline picolinic acid N-oxide. A new computational approach and infrared, raman and INS study

Infrared, Raman and INS spectra of picolinic acid N-oxide (PANO) were recorded and examined for the location of the hydronic modes, particularly O-H stretching and COH bending. PANO is representative of strong chelate hydrogen bonds (H-bonds) with its short O...O distance (2.425 A). H-bonding is possibly well-characterized by diffraction, NMR and NQR data and calculated potential energy functions. The analysis of the spectra is assisted by DFT frequency calculations both in the gas phase and in the solid state. The Car-Parrinello quantum mechanical solid-state method is also used for the proton dynamics simulation; it shows the hydron to be located about 99% of time in the energy minimum near the carboxylic oxygen; jumps to the N-O acceptor are rare. The infrared spectrum excels by an extended absorption (Zundel's continuum) interrupted by numerous Evans transmissions. The model proton potential functions on which the theories of continuum formation are based do not correspond to the experimental and computed characteristics of the hydrogen bond in PANO, therefore a novel approach has been developed; it is based on crystal dynamics driven hydronium potential fluctuation. The envelope of one hundred 0 --> 1 OH stretching transitions generated by molecular dynamics simulation exhibits a maximum at 1400 cm-1 and a minor hump at approximately 1600 cm-1. These positions square well with ones predicted for the COH bending and OH stretching frequencies derived from various one- and two-dimensional model potentials. The coincidences with experimental features have to be considered with caution because the CPMD transition envelope is based solely on the OH stretching coordinate while the observed infrared bands correspond to heavily mixed modes as was previously shown by the normal coordinate analysis of the IR spectrum of argon matrix isolated PANO, the present CPMD frequency calculation and the empirical analysis of spectra. The experimental infrared spectra show some unusual characteristics such as large temperature effects on the intensity of some bands, thus presenting a challenge for theoretical band shape treatments. Our calculations clearly show that the present system is characterized by an asymmetric single well potential with no large amplitudes in the hydronium motion, which extends the existence of Zundel-type spectra beyond the established set of hydrogen bonds with large hydronic vibrational amplitudes.     

Direct structural identification of polysaccharides from red algae by FTIR microspectrometry II: Identification of the constituents ofGracilaria verrucosa

The use of the infrared microspectrometry analytical technique as a new tool for the identification of the polysaccharides contained in the red algaeGracilaria verrucosa has demonstrated that in addition to agar spectra, features of the other coexisting constituents can also be obtained. Indeed, the infrared spectra recorded previously, all exhibit two important bands at about 1645 and 1530cm^–1. These two bands were not present in the infrared spectra of the extracted agars and they are expected to be due to the amide I and amide II protein vibrations. In order to confirm this supposition, we have applied some enzymatic treatments, firstly on the whole algae and secondly on the ground algae (the algae has been previously depigmented and then dehydrated). Agarase, xylanase and cellulase were successively carried out on the algae. The last resulting spectrum, i.e. the spectrum obtained from the fraction which has undergone the three treatments, has been identified to be characteristic of proteins. This spectrum contained, both the amide I and II vibrations and in addition, weak absorption at 1230 cm^–1 due probably to the amide III, was observed. Additional weak bands in the 1400–1300 cm^–1 due to the different skeletal modes of the proteins were also present in this spectrum.The infrared spectra also revealed that the use of the enzymatic treatments on the ground algae is more efficient than when it is carried out on the whole algae.     

Study of anomalous infrared properties of nanomaterials through effective medium theory

Effective medium theory is introduced into a three-layer model to study the anomalous IR properties of nanostructured Pt films. A composite system is set up for the nanostructured film together with adsorbates and water around it. The anomalous IR spectral features, which exhibit a transition from enhanced (or normal) IR absorption to Fano-type bipolar line shape and, finally, to enhanced anomalous IR absorption (the abnormal infrared effects) along with the change in structure and size of nanomaterials, as observed through experiments for CO molecule adsorption, are elucidated by an increase in the volume fraction of metal in the composite system and the effective thickness of the composite system. The theoretical simulation results illustrate that the spectral line shape of IR absorption depends strongly on the volume fraction of metal, while the intensity of the IR band is directly proportional to the effective thickness. This study has revealed, through a physical optical aspect of interaction of CO molecules with nanostructured metal films, one of the possible origins of anomalous IR properties and has shed light on interpreting the peculiar properties of nanomaterials.     

鞋底材料的傅立叶变换红外光谱类型分析

利用傅立叶变换红外光谱技术对收集的29种皮鞋类黑色鞋底样品进行了测定分析,其中24种样品来自不同品牌或型号,5种样品来自同一品牌同一厂家同一批次.从红外光谱图中可以看出,依据红外光谱图中特征峰的峰数、峰位、峰形可将29个鞋底样品分为3大类.同一大类的部分鞋底样品有着相似的红外光谱特征,但在相对峰高比和指纹区中一些弱吸收峰上仍然存在明显差异.同一品牌同一厂家同一批次的鞋底样品红外光谱特征基本一致.这表明傅立叶变换红外光谱法是鉴别鞋底材料的有效方法,可以为案件现场遗留的各种鞋底材料残渣及其擦痕提供种属鉴别及比对分析.     

Rapid discrimination of Eurycoma longifolia extracts by Fourier transform infrared spectroscopy and two dimensional correlation infrared spectroscopy

Eurycoma longifolia is a herbal medicinal plant of South-East Asian origin, popularly recognized as ‘Tongkat Ali’. The root extracts have been used in indigenous traditional medicines for its unique antimalarial, anti-pyretic, antiulcer, cytotoxic and aphrodisiac properties. It is an important task that fast and effective analysis methods monitor the inherent qualities of traditional herbal medicines and its corresponding extracts products as a complicated mixture system. Owing to the unique fingerprint character and extensive applicability to test sample, infrared spectral method have been used in many research fields. In this paper, we use FT-IR, second derivative infrared spectroscopy and two-dimensional correlation infrared spectroscopy (2D-IR) step by step to analyze E. longifolia and its different extracts (extracted by hexane, ethyl acetate, dichloromethane and methanol in turn). The findings indicated that FT-IR and 2D-IR can provide many holistic variation rules of chemical constituents. The structural information of the samples indicated that E. longifolia and its extracts contain a large amount of quassinoids, since some characteristic absorption peaks of quassinoids, such as ∼1700 cm⁻¹, ∼1670 cm⁻¹, ∼1600 cm⁻¹,∼1500 cm⁻¹, and ∼1270 cm⁻¹ can be detected. This method, having its high resolution and excellent macroscopic fingerprint features, can not only supply lots of structural information of main components in the complicated system, but also can differentiate the tiny differences between the similar systems according to the macro-fringerprint characters. This method is highly rapid, effective, accurate and well repetitive for pharmaceutical research.     

Industrial applications of computerized dispersive infrared spectroscopy for analysis in solution

Today, with the relatively low cost of data processing equipment, it is possible to interface a dedicated minicomputer to a computer-compatible scientific instrument to give a total system that is ideal for routine operation. This article describes some basic chemical applications of a commercial system for computerized infrared spectroscopy that are relevant to analytical problems encountered in industrial laboratories. In the initial stages of the article some examples are given of the different experimental procedures that are available to handle infrared data from solutions. The remaining sections illustrate the direct application of data handling to specific applications in both organic and aqueous media.     

Coordination behaviour of benzothiazolines towards iron(II)

Summary This paper describes the synthesis and structural features of iron(II) complexes of some biologically active benzothiazolines derived by the condensation of various aldehydes and ketones such as pyridine 2-aldehyde, furfuraldehyde, thiophene-2-aldehyde, indole-3-carboxaldehyde, benzil, biacetyl, glyoxal, and terpthaldehyde with 2-aminothiophenol. An attempt has been made to characterize the resulting complexes by elemental analysis, conductance measurement, molecular weight determination and electronic, infrared,¹H and¹³C n.m.r. spectral studies. An octahedral geometry has been suggested on the basis of magnetic measurements and Mössbauer spectra.     

一种新型在线近红外光谱分析仪的研制

研制了一种新型的电荷耦合器件(CCD)在线近红外光谱分析仪，它由光谱仪系统、电源电路与控制系统、光纤及其附件与流通池系统、防爆系统、样品前处理系统、模型界外样品抓样系统、实时光谱测量和化学计量学软件等部分组成。在兰州炼油厂联合重整装置上连续5个月的工业实验表明，该仪表测定汽油辛烷值的准确性为0．3个辛烷值单位，重复性为0．2个辛烷值单位，具有准确性高、稳定性好、测量速度快、安全性强、自动化程度高和分析测试项目扩展性宽等特点。该仪表可与APC技术或其它自动化系统联用，对石化等大型生产装置的技术进步将产生积极的推动作用。