The mechanism of the dissolution,spray and deposition technique--a novel infrared sampling method

The dissolution, spray and deposition (DSD) technique, a novel infrared (IR) sampling technique, gives very sharp spectra for amino acids and peptides. The mechanism of this unique technique has been established by scanning electron microscopy (SEM) studies and found to be due to the formation of several layers of fairly large KBr crystals in situ on an IR transparent window. The zwitterions of the amino acids and dipeptides are adsorbed on the surface of these large KBr crystals, which ensures the isolation of monomers of the amino acid or dipeptide zwitterions in the KBr matrix, thereby leading to sharp and well-resolved IR spectra. This methodology provides a powerful IR sampling technique, akin to matrix isolation, with the added advantage of being extremely cost effective as it does not require low-temperatures or a sophisticated experimental set up.     

Microcolumn liquid chromatography/Fourier transform infrared spectrometry interface using a potassium bromide disk

Summary A redesigned interface is reported for use in the detection of microcolumn liquid chromatographic effluents with a Fourier transform infrared spectrometer. The solutes eluting from the column are continuously deposited onto a 50mm diameter KBr disk as a “buffer-memory”. The disk is rotated by a stepper motor with a controlling electronics. After the chromatographic run, the disk is simply transferred to the spectrometer and the transmission spectra are measured as the disk rotates. The use of such a large KBr disk as a substrate permits to obtain spectra of the components having a large capacity factor.     

Diffuse reflectance spectroscopy of powders

Diffuse reflectance (DRIFT) spectra in the mid-IR region, especially of inorganic powders, often reveal inverted or derivative-like structures (“reststrahlen” bands) which make their straightforward interpretation in terms of the Kubelka-Munk theory difficult. A simulation technique based on a combination of single scattering (Mie theory) and radiative transfer (with Kubelka-Munk as a special case) is reported that allows measured DRIFT spectra to be described without use of any free “fit” parameters. The results for silica glass microspheres and silicon carbide powder show that not specular reflectance but prominent structures in the single particle scattering cross-section are responsible for the reststrahlen features which cannot be suppressed even by diluting the powder in an excess of KBr. The efficiency of a “blocker” device in DRIFTS is also discussed.     

The infrared spectra and structures of the valyl-glycine zwitterion isolated in a KBr matrix

The IR absorption spectrum of zwitterions of l-valyl-glycine isolated in a KBr matrix has been measured using a novel dissolution, spray and deposition technique. The number of conformers, their molecular structures and their vibrational spectra have been determined by ab initio molecular orbital calculations of the non-aqueous self-consistent reaction field type, using the Onsager dipole-sphere model at both the density functional theory and Hartree–Fock levels. Six conformers were determined. Although differences in their relative energies were found to be small, one conformer Tg2 was consistently the lowest for a range of cavity radii and for both levels of theory. From comparison of the observed and predicted spectra it is concluded that one or more of the trans group of conformers is present in the KBr matrix. Good agreement between measured and calculated spectra has been obtained for the majority of the prominent bands in the spectrum.     

Infrared study of HDTMA+ intercalated montmorillonite

In this paper, FTIR spectroscopy using attenuated total reflection (ATR) and KBr pressed disk techniques has been used to characterize sorbed water and HDTMA+ in organo-clay. Sorbed water content decreases with the intercalation of HDTMA+. With the decrease of the sorbed water content, the position of the nu2 mode shifts to higher frequency dramatically while the stretching vibration shifts to lower frequency slightly, indicating that H2O is less strongly hydrogen bonded. This might be resulted from the polarization of H2O molecules by the changeable cations and HDTMA+. FTIR spectra show that both antisymmetric and symmetric CH2 stretching absorption bands shift to low frequencies with increase of amine concentration within the galleries of montmorillonite, elucidating the increase of ordered conformation. Furthermore, the present study demonstrates that the antisymmetric CH2 stretching mode is more sensitive to the conformational ordering than the symmetric stretching mode. When KBr pressed disk technique used, two well resolved absorption bands at 730 and 720 cm(-1), and at 1473 and 1463 cm(-1), corresponding to the methylene scissoring and rocking modes, respectively, could be observed in FTIR spectra of organo-clays with relative higher concentration of surfactant. However, the FTIR spectra using ATR technique only display singlets and they are independent of amine concentration and chain conformation. Our present study demonstrates that FTIR spectroscopy using KBr pressed disk technique is more suitable to probe the conformational ordering of surfactant in organo-clays than that suing ATR technique does.     

β-(5-Methyl-4-phenylpyridin-2-yl)alkanols

The -lithiomethyl derivative obtained by the metallation of 2,5-dimethyl-4-phenylpyridine with methyllithium has been used in the synthesis of several alcohols of the pyridine series.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 8, pp. 1086–1087, August, 1970.The IR spectra given in this paper were recorded on a UR-20 spectrophotometer in the 3800–400 cm^– region using LiF, NaCl, and KBr prisms. Samples II and V were prepared in the form of tablets with KBr. Samples III and IV were prepared in the form of mulls is praffin oil.     

A Correction to the Hydrogen Atoms Coordinates for Tris(dimethylamino)phosphinoxide in the Solid Adduct [(CH3)2N]3PO · 2 S7NH

Infrared Spectroscopic Investigation of the Products by the Preparation of Million's Base. The reaction product of a mixture of HgO + KBr with NH₃ and H₂O is dried by different methods. From all these species, also from the product of HgO + KBr and dry Ammonia, infrared spectra were taken and discussed as stoichiometric compounds between HgO and Millon's Base.     

Qualitative analysis of green coffee by infrared spectrometry

Principal component analysis and linear discriminant analysis (LDA) were applied to the mid-infrared spectra for the qualitative analysis of the variety of green coffee (Arabica and Robusta). It is shown that the KBr pellet technique in combination with the LDA method can successfully be used for the identification of sample origin.     

Qualitative analysis of green coffee by infrared spectrometry

Principal component analysis and linear discriminant analysis (LDA) were applied to the mid-infrared spectra for the qualitative analysis of the variety of green coffee (Arabica and Robusta). It is shown that the KBr pellet technique in combination with the LDA method can successfully be used for the identification of sample origin.     

Background Reduction in IR Spectroscopy Using a Highly Scattering Filter

Abstract

There are many methods for measuring FT-IR spectra, for example, transmission, diffuse reflection, attenuated total reflection and so on. It is said that the transmission method is the most reliable method for qualitative and quantitative analysis of FT-IR spectra. The spectra of highly scattering samples such as coals or amorphous silicon powders measured by the transmission method, however, have large backgrounds with small relevant absorption peaks. Therefore, we investigated measuring methods for reducing the background itself. As a result, using a highly scattering 1R filter, we could clearly distinguish absorption peaks of amorphous silicon powders that were not found in IR spectrum measured by the normal transmission method. Our highly scattering filter is composed of fine Csl powders(<125?10 ^?6m) and fine KBr powders(<125?10^?6m).     

Infrarotanalyse von Submikrogramm-Mengen

By combination of the micro specular reflectance method with electronic time averaging infra-red spectra of nanogram amounts become measurable. The sample material must be sufficiently stable over the period of registration (some hours). The comparison of the KBr micro pellet technique and the micro specular reflectance method demonstrates some advantages of the latter if less sample material is available than a few micrograms.     

Vibrational spectra of WO3·nH2O and WO3 polymorphs

Vibrational spectra of polycrystalline WO₃ hydrates and polymorphs were measured and analyzed. The effect of sampling techniques on IR spectra has been demonstrated. The phase transition into triclinic polymorph (C⁵_2 h → C¹_i) has been revealed for the sample of monoclinic WO₃ prepared as KBr pellet. Using the deuteration method in situ has shown that cubic WO₃ is non-stoichiometric oxide stabilized by residual OH groups of WO₃·H₂O precursor.     

Laser Raman and IR spectra and force fields for 2,6-difluorobenzonitrile

Raman spectrum of 2,6-difluorobenzonitrile in the powder form has been recorded in the region 50–4000 cm⁻¹ on a Jasco K-500 spectrophotometer using the 488.0 nm radiation from an argon laser. IR spectra in the region 200–4000 cm⁻¹ have been recorded in KBr pellet and nujol mull on a Nicolet DX spectrometer and in liquid and vapour phases on a Jasco FTIR/7000 spectrometer. Using these observed frequencies force field calculations for the planar and non-planar modes have been carried out assuming a general valence force field.     

Effect of concentration, particle size and the presence of protective coatings in DRIFT spectra of building materials

This paper discusses the effect of particle size (from under 45 to 425 μm), sample concentration (5 and 50% dilution in KBr) and the presence/absence of anti-graffiti coatings on the quality of diffuse reflectance spectra, specifically the spectra for limestone, granite and brick. In limestone, sample dilution was found to affect spectral resolution significantly, whereas the increase in particle size leads to a slight decrease in signal intensity. The presence of anti-graffiti protection was the factor that disturbed spectral quality most visibly, except in very dilute (5%) samples with a very fine particle size (under 45 μm). In more heterogeneous materials such as brick and granite, particle size proved to have a greater impact than dilution, while the presence of protective treatment was again the parameter with the greatest effect on quality and consequently signal reproducibility. This effect was slighter in very dilute samples with a small particle size.     

苯甲醇对CTAB/KBr胶束体系流变性及CTAB分子1HNMR谱影响的研究

报道了苯甲醇对CTAB/KBr胶束体系粘度的影响,利用1HNMR法研究了苯甲醇在CTAB胶束中的增溶位置.结果表明,在KBr盐溶液中,随着苯甲醇的加入,0.01mol/LCTAB胶束体系的粘度增大至最大值.对CTAB分子的1HNMR分析表明,少量的苯甲醇增溶在棒状胶束的界面,促使胶束体积增大和相互缠结,体系的粘度随之增大;当苯甲醇浓度较高时,将增溶在胶束的栅栏层靠近极性头一侧,胶束发生棒-球转变和解缠,体系的粘度降低.     

Effect of sample packing on the scattering properties of the reference material in diffuse reflectance infrared spectrometry

Effect of the sample packing on the scattering properties of KBr, one of the most conventional matrix used in diffuse reflectance Fourier transform infrared (IR) spectrometry (DRIFTS), has been studied. The particle size of KBr ranged between 2 and 15 mum with a mean of 9.9 mum. The average particle size of quartz and calcite used as analytes were 2 mum and 6 mum, respectively. The scattering coefficient of KBr has been found to increase with increasing pressure applied during sample packing. 1 MPa pressure was necessary for reproducible scattering properties and quantitative results. The scattering coefficient of KBr using 1 MPa pressure for 1 min during sample packing has been determined from calibration curves and found to be as s = 107 +/- 11 cm(-1). It has been experimentally demonstrated that using 2 mm deep sample cups, the criteria of infinite sample thickness is practically fulfilled. It has been also shown that band intensities of reflectance spectra were strongly influenced by the change of the reflectance of the reference material and the less the sample concentration (c) the greater the effect. If c < 0.1 w/w%, that often occurs in practice, the RSD of band intensities can vary upto +/- 10-60%. Therefore, in quantitative analysis all spectra should be measured against one and same sample of reference material.     

Anomalous infrared spectra of diazepam in potassium bromide pellets prepared from chloroform solutions

When diazepam in chloroform was incorporated into a KBr pellet, its infrared (i.r.) spectrum showed an anomalous spectral phenomenon at 836 cm^?1. Examination of i.r. spectra of diazepam obtained by the solution, multiple-internal-reflectance, and KBr-pellet techniques suggest that this spectral characteristic is due to the orientation effect of diazepam in KBr pellets.     

THE EFFECT OF BENZYL ALCOHOL ON THE MICELLAR PROPERTIES OF CTAB IN KBr SOLUTION

ABSTRACT

The effect of benzyl alcohol on the micellar size and shape of CTAB in KBr solution has been investigated by means of viscosity, LLS (laser light scattering), and NMR measurements. The surfactant CTAB (cetyltrimethylammonium bromide) and KBr content are kept constant at 0.01 mol.L^?1 and O.l^?1 mol.. The data from the various techniques are quantitatively in agreement. The viscosity of 0.01 mol.L^?1 CTAB/ 0.01mol.L^?1 KBr micellar system has a marked maximum at benzyl alcohol content 0.6%(v/v), where the size of rod micelles are largest. The results from 'H-NMR spectra of CTAB molecules show that before the maximum viscosity, benzyl alcohol is located in the interfacial region of CTAB micelles in the presence of KBr salt. If more benzyl alcohol is added, it starts solubilizing in the palisades of the micelles.     

Correlation of structure and vibrational spectra of the zwitterion L-alanine in the presence of water: an experimental and density functional analysis

Infrared vibrational spectra were collected along with the vibrational circular dichroism (VCD) spectra for the zwitterions alpha-D-alanine, alpha-L-alanine, alpha-D-mannose and alpha-L-mannose as potassium bromide (KBr) pressed samples. VCD for D- and L-alanine dissolved in water was also measured and compared against the spectra resulting from KBr pressed samples. The experimental data were compared against the ab initio B3LYP/6-31G* optimized geometry. The zwitterion structure of alpha-L-alanine was stabilized by the addition of water molecules. Computationally, beta-L-mannose was studied and resulting expected VCD bands assigned. We present the molecular structures resulting VCD spectra and infrared vibrational spectra from experimentation as compared with the computed results.     

Influence of alkaline earth metals on molecular structure of 3-nitrobenzoic acid in comparison with alkali metals effect

The influence of beryllium, magnesium, calcium, strontium and barium cations on the electronic system of 3-nitrobenzoic acid was studied in comparison with studied earlier alkali metal ions [1]. The vibrational FT-IR (in KBr and ATR techniques) and ¹H and ¹³C NMR spectra were recorded for 3-nitrobenzoic acid and its salts. Characteristic shifts in IR and NMR spectra along 3-nitrobenzoates of divalent metal series Mg → Ba were compared with series of univalent metal Li → Cs salts. Good correlations between the wavenumbers of the vibrational bands in the IR spectra for 3-nitrobenzoates and ionic potential, electronegativity, inverse of atomic mass, atomic radius and ionization energy of metals were found for alkaline earth metals as well as for alkali metals. The density functional (DFT) hybrid method B3LYP with two basis sets: 6-311++G** and LANL2DZ were used to calculate optimized geometrical structures of studied compounds. The theoretical wavenumbers and intensities of IR spectra as well as chemical shifts in NMR spectra were obtained. Geometric aromaticity indices, atomic charges, dipole moments and energies were also calculated. The calculated parameters were compared to experimental characteristic of studied compounds.