Infrared Spectroscopy Methods Research Articles

Microwave non-destructive testing technique for characterization of HPMC-PEG 3000 films

The capacity of microwave non-destructive testing (NDT) technique to characterize the matrix property of binary polymeric films for use as transdermal drug delivery system was investigated. Hydroxypropylmethylcellulose (HPMC) and polyethylene glycol (PEG) 3000 were the choice of polymeric matrix and plasticizer, respectively with loratadine as the model drug. Both blank and drug loaded HPMC-PEG 3000 films were prepared using the solvent-evaporation method. These films were conditioned at the relative humidity of 25, 50 and 75% prior to physicochemical characterization using the established methods of ultra-violet spectrophotometry, differential scanning calorimetry and Fourier transform infrared spectroscopy methods, as well as, novel microwave NDT technique. Blank films exhibited a greater propensity of polymer–polymer interaction at the O–H domain upon storage at a lower level of relative humidity, whereas drug loaded films exhibited a greater propensity of polymer–polymer, polymer–plasticizer and/or drug–polymer interaction via the O–H, C–H and/or aromatic C C functional groups when they were stored at a lower or moderate level of relative humidity. The absorption and transmission characteristics of both blank and drug loaded films for microwave varied with the state of polymer–polymer, polymer–plasticizer, and/or drug–polymer interaction of the matrix. The measurements of microwave NDT test at 8 and 12 GHz were sensitive to the polar fraction of film involving functional group such as O–H moiety and the less polar environment of matrix consisting of functional groups such as C–H and aromatic C C moieties. The state of interaction between polymer, plasticizer and/or drug of a binary polymeric film can be elucidated through its absorption and transmission profiles of microwave.

Process Analytical Technology: Chemometric Analysis of Raman and Near Infra-Red Spectroscopic Data for Predicting Physical Properties of Extended Release Matrix Tablets

The purpose of this work was to develop a correlation between pharmaceutical properties such as hardness, porosity, and content with prediction models employed using Raman and near infra-red (NIR) spectroscopic methods. Metoprolol tartrate tablets were prepared by direct compression and wet granulation methods. NIR spectroscopy and chemical imaging, and Raman spectra were collected, and hardness, porosity, and dissolution were measured. The NIR PLS model showed a validated correlation coefficient of >0.90 for the predicted versus measured porosity, hardness, and amount of drug with raw and second derivative NIR spectra. Raman spectra correlated porosity of the tablets using raw data for directly compressed tablets and wet granulated tablets (r(2) > 0.90). A very close root-mean square error of calibration (RMSEC) and root-mean square error of prediction (RMSEP) values were found in all the cases indicating validity of the calibration models. Raman spectroscopy was used for the first time to predict physical quality attribute such as porosity successfully. Chemical imaging utilizing NIR detector also demonstrated to show physical changes due to compression differences. In conclusion, sensor technologies can be potentially used to predict physical parameters of the matrix tablets.

Study of the effect of Cal-Red on the secondary structure of human serum albumin by spectroscopic techniques

The effect of Cal-Red on the structure of human serum albumin (HSA) was studied using Resonance light scattering (RLS), Fourier transformed Infrared (FT-IR) and Circular dichroism (CD) spectroscopic methods. The RLS spectroscopic results show that the RLS intensity of HSA was significantly increased in the presence of Cal-Red. The binding parameters of HSA with Cal-Red were studied at different temperatures of 289, 299, 309 and 319 K at pH 4.1. It is indicated by the Scatchard plots that the binding constant K decreased from 4.03 × 10 8 to 7.59 × 10 7 l/mol and the maximum binding number N decreased from 215 to 152 with increasing the temperature, respectively. The binding process was exothermic and spontaneous, as indicated by the thermodynamic analyses, and the major part of the binding energy is hydrophobic interaction. The enthalpy change Δ H 0, the free energy change Δ G 0 and the entropy change Δ S 0 of 289 K were calculated to be −42.75 kJ/mol, −47.56 kJ/mol and 16.66 J/mol K, respectively. The alterations of protein secondary structure in the presence of Cal-Red in aqueous solution were quantitatively calculated from FT-IR and CD spectroscopy with reductions of α-helices content about 5%, β-turn from 10% to 2% and with increases of β-sheet from 38% to 51%.

Interference of Saturated Fats in the Determination of Low Levels of trans Fats (below 0.5%) by Infrared Spectroscopy

AbstractThe mandate to label food products with the content of total trans fatty acids has led to an increase in demand for sensitive and accurate methodologies for the rapid quantitation of trans fats. Unfortunately, the latest official infrared (IR) spectroscopic method lacks the required sensitivity. A more sensitive IR procedure that requires the measurement of the height of the second derivative (2D) of the trans absorption band at 966 cm−1 was recently proposed; however, a reported inconsistency at low trans levels between GC (0% of total fat) and IR (1.2% of total fat) results for a fully hydrogenated vegetable oil could not be reconciled, and triggered further investigations. For the first time, we recognize and report the presence of weak interference bands (962–956 cm−1) attributed to saturated fats in the IR spectra of trans fats; these interference bands have an adverse impact on the sensitivity and accuracy of the IR determination at low trans levels (≤0.5% of total fat). Therefore, weak spectral features observed at energies below the one expected for trans bands (966 cm−1) in test samples high in saturated fat (coconut oil and cocoa butter) must not be mistaken for trans bands.

The effects of maleic anhydride terpolymer and its ester derivatives on tensile bond strength between the acrylic resin and resilient lining material

AbstractThe present study investigated the effects on the bonding between the denture base acrylic resin and the soft silicon based lining material of maleic anhydride‐styrene‐vinyl acetate (MA‐St‐VA) terpolymer and some of its ester derivatives. These ester derivatives were n‐propylmaleate‐styrene‐vinyl acetate (n‐PrMA‐St‐VA), n‐buthylmaleate‐styrene‐vinyl acetate (n‐BuMA‐St‐VA) and n‐benzylmaleate‐styrene‐vinyl acetate (n‐BzMA‐St‐VA). Fourier Transform infrared spectroscopy method was used to determine interactions between terpolymers with the acrylic resin and soft lining material. The tensile bond strength of all the groups was compared and the obtained differences were statistically significant (P < 0.05). The highest value was found for the samples lined with n‐BuMA‐St‐VA (2.11 ± 0.21 MPa) and the samples lined with n‐BzMA‐St‐VA had the lowest bond strength (0.3 ± 0.12 MPa). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1338–1341, 2007

Synthesis of organo-layered double hydroxides by an environmentally friendly co-hydration route

Environmentally attractive synthetic routes are studied for the synthesis of MgAl-layered double hydroxides (LDHs) incorporating a series of organic dicarboxylate anions. The reaction conditions are systematically explored to ascertain the effect of acid chain length and layer charge (i.e. Mg/Al ratio). The materials are characterised by powder X-ray diffraction, scanning electron microscopy, infra-red spectroscopy and thermal methods. The effect of reaction conditions on product purity and the packing arrangement of the intercalated organic molecules is reported, with impurity free organo-LDHs observed at Mg/Al = 2 and increased interlayer packing as Mg/Al approaches 1.

Chemical imaging of the stratum corneum under controlled humidity with the attenuated total reflection Fourier transform infrared spectroscopy method

Attenuated total reflection Fourier transform infrared spectroscopic imaging was applied to study human stratum corneum (SC) tissue, the outermost layer of the skin. This imaging approach was combined with a controlled environment cell to demonstrate the possibility of obtaining chemical images of SC exposed to a wide range of relative humidities and diffusion of ethanol through the SC tissue with a specially designed liquid cell. The effect of water vapor sorbed into the SC on the distribution of other components in the SC was studied. Principal component analysis was applied in conjunction with univariate analysis to differentiate the distribution of different components in the SC. Swelling of the SC, a heterogeneous distribution of natural moisturizing factor and water, was detected upon the increase of relative humidity. The approach to image the penetration of liquid ethanol into the SC was also demonstrated and showed good potential and implications for studying transdermal drug delivery.

Impact of potassium on the heats of adsorption of adsorbed CO species on supported Pt particles by using the AEIR method

The heats of adsorption at several coverages of the linear and bridged CO species (denoted L and B, respectively) adsorbed on the Pt 0 sites of the 2.9 wt% Pt/10% K/Al 2O 3 catalyst are determined using the Adsorption Equilibrium Infrared spectroscopy method. The addition of K on 2.9% Pt/Al 2O 3 modifies significantly the adsorption of CO on the Pt particles: (a) the ratio L/B is decreased from 8.4 to 1, (b) a new adsorbed CO species is detected with an IR band at 1763 cm −1, (c) the heats of adsorption of L and B CO species are significantly altered and the positions of their IR bands are shifted. The heats of adsorption of L CO species are decreased: i.e. 206 and 105 kJ/mol at low coverages on Pt/Al 2O 3 and Pt/K/Al 2O 3 respectively. Two B CO species denoted B1 and B2, with different heats of adsorption are observed on Pt/K/Al 2O 3. The heats of adsorption of B2 CO species (major B CO species) are significantly larger than those measured in the absence of K: i.e. 94 and 160 kJ/mol at low coverages on Pt/Al 2O 3 and Pt/K/Al 2O 3 respectively, whereas those of B1 CO species (minor species) are similar: 90 kJ/mol at low coverages. These values are consistent with the qualitative High Resolution Electron Energy Loss Spectrometry literature data on Pt(1 1 1) modified by potassium.

Infrared Kinetic/Structural Studies of Barrier Reformation in Intact Stratum Corneum following Thermal Perturbation

Stratum corneum, the outermost layer of the epidermis, constitutes the main barrier to permeability in skin. As such, it has been the target of many approaches for transdermal drug delivery based on methods involving transient modifications of the barrier. An infrared (IR) spectroscopic method has been developed to monitor the kinetics of barrier restoration following an external perturbation. In the current case, temperature perturbation was selected as a convenient means to induce structural changes in the barrier. The method is based on the observation that the ordered lipid phases of the barrier in isolated human stratum corneum exist in part in orthorhombically packed subcells. Such phases display a characteristic splitting of the CH2 rocking vibrations with component frequencies at 720 and 729 cm(-1). The latter is reliably diagnostic for orthorhombic phases and is markedly reduced in intensity following a thermal perturbation to 55 degrees C. The kinetics of barrier recovery following quenching to either 25 degrees C or 30 degrees C were monitored by tracking the restoration of the 729 cm(-1) band intensity. The kinetics were dominated by exponential growth in the initial stages, followed by linear increases at longer times. The half lives for exponential growth regimes were 52.4 h for the 25 degrees C quench and 13.8 h for the 30 degrees C quench. These values are in reasonable accord with those determined with more phenomenological approaches, typically based on restoration of some barrier function. This novel method for monitoring structural reorganization kinetics in intact stratum corneum can readily be extended to evaluate barrier recovery following a variety of treatments used to enhance drug delivery.

Phosphorus Sensing for Fresh Soils using Visible and Near Infrared Spectroscopy

Fast, precise and affordable soil analytical techniques are needed for the determination of soil fertility of each zone of a field in site-specific land management. The objective of this study was to develop a reliable calibration model with the visible (VIS) and near infrared (NIR) spectroscopy method to predict the phosphorus (P) content in fresh soil as a preliminary step towards the development of an automated variable rate fertiliser distributor. The Zeiss Corona® 45 visnir fibre-type spectrophotometer was used to measure soil spectra in reflectance mode in the wavelength range of 305–1710 nm. A total of 185 soil samples were collected from arable fields and grassland distributed over Flanders (Belgium) amended with 29 and 14 samples taken from two fields near Leuven, (Belgium) to obtain a balanced P data set. Only samples with texture classes of silt loam, sandy loam and loamy sand texture were held, to avoid possible averse effects of small amounts of soil samples with different textures. Fresh samples were subject to chemical analyses and optical reflectance measurements. Soil spectra were correlated with available P using the partial least-squares (PLS) regression and full cross-validation. After removing the noise, the VIS-NIR wavelengths in the range 401–1663 nm were used. From the same data set, two suitable calibration models were developed using different data pre-processing methods. In the validation stage both models predicted available P in the soil with a coefficient of determination R2 of 0·75 and 0·73. On two extra date sets (126 and 36 samples, collected from two fields near Leuven), both models were evaluated. The prediction of P on these samples, provided acceptable results (R2=0·68 and 0·63). The two P models, developed in this research, can be used for rapid prediction of P in fresh soil samples in the laboratory and in situ in fields in Flanders having texture classes: loamy sand, sandy loam and silt loam. This detailed information could be employed to provide input to master a site-specific P management. These promising P models could lead to provide the necessary information for an automatic adaptation of the fertiliser rates of a P applicator.

Spectroscopic evidences of EDTA interaction with inorganic supports during the preparation of supported metal catalysts

Chelating compounds (etylenediaminetetraacetic acid (EDTA)-type reagents) are broadly applied in many chemical processes. One of the possible applications is their use in the preparation of the catalysts. A short summary based on my own experience in the spectroscopic studies on chelating molecules interaction with the surface of inorganic oxides is presented. The application of spectroscopic techniques allow to describe the nature and type of interactions. Particularly, the experiments conducted by an infrared spectroscopy method deliver valuable information which is of great importance for the adsorption and catalytic investigations.

Determination of the degree of substitution, degree of amidation and degree of blockiness of commercial pectins by using capillary electrophoresis

It is more and more realised that pectins are complex mixtures of many different molecules and research is directed towards the fractionation and characterisation of these pectic sub-populations. Since fractionation of pectins generally results in only low amounts of purified material, rapid characterisation methods using low amounts of samples are required. In this study, capillary electrophoresis was chosen to characterise pectins because only tiny amounts of sample are needed for the analysis. A new capillary electrophoresis (CE) protocol was developed to determine the degree of amidation, the degree of methyl-esterification (DM) and consequently the degree of substitution (DS) of pectins by analysing the pectins before and after removal of the methyl-esters. The CE results were compared with results obtained for the same pectins by using titration and Fourier transform infra-red (FTIR) spectroscopy methods. The CE method was found to be rather reliable resulting in small standard deviations for the DS and DAm. The CE method had the advantage of being rapid due to the limited sample preparation and automation of the analysis. In addition, CE was used successfully to determine the degree of blockiness of the free GalA residues over the pectic backbone.

Forensic classification of ballpoint pen inks using high performance liquid chromatography and infrared spectroscopy with principal components analysis and linear discriminant analysis

Several varieties of blue ballpoint pen inks were analyzed by high performance liquid chromatography (HPLC) and infrared spectroscopy (IR). The chromatographic data extracted at four wavelengths (254, 279, 370 and 400 nm) was analyzed individually and at a combination of these wavelengths by the soft independent modeling of class analogies (SIMCA) technique using principal components analysis (PCA) to estimate the separation between the pen samples. Linear discriminant analysis (LDA) measured the probability with which an observation could be assigned to a pen class. The best resolution was obtained by HPLC using data from all four wavelengths together, differentiating 96.4% pen pairs successfully using PCA and 97.9% pen samples by LDA. PCA separated 60.7% of the pen pairs and LDA provided a correct classification of 62.5% of the pens analyzed by IR. The results of this study indicate that HPLC coupled with chemometrics provided a better discrimination of ballpoint pen inks compared to IR. The need to develop a suitable IR method for analysing blue ballpoint pen inks has been emphasized and it is hoped that the development of such a method would indeed provide a valuable tool for the non-destructive analysis of blue ballpoint pen ink samples for forensic purposes.

Solvent-induced partial cyanoethylation and hydroxylation of cyanoethyl group

An investigation has been made on the cyanoethylation of cotton fabric using aqueous sodium hydroxide with acrylonitrile in presence of solvents acetone and ethanol at different concentrations. The hydrolysis of β-cyanoethyl ether of cyanoethylated fabric in presence of solvents is studied. The rate of hydrolysis is enhanced by acetone and ethanol concentration. The formation of various products during hydrolysis is analyzed by infrared spectroscopy method while scanning electron microscopy follows the variations in surface morphology. Some of the physical and chemical properties are also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 183–191, 2006

Infrared Spectroscopic Characterization of Polymer and Clay Platelet Orientation in Blown Films Based on Polypropylene‐Clay Nanocomposite

AbstractThe “tilted film” transmission infrared spectroscopy method was used to characterize the biaxial orientation in a set of blown films containing polypropylene (PP), layered silicate nano‐reinforcement, and two different compatibilizing agents based on maleic‐anhydride‐grafted PP. Both interactive spectral subtraction and peak fitting were used to determine trichroic ratios. The biaxial orientation of the polymer chains could be clearly quantified according to well‐established relationships for PP. In addition, the clay platelet orientation could be determined from the trichroism of the SiO stretching bands around 1100 – 1000 cm−1. The clay orientation was found to be quite high (Hermans orientation function around +0.8) and was not significantly affected by the presence of compatibilizing agent.

Adsorption of 2-mercaptobenzimidazole on a Au(1 1 1) electrode

The description of the monolayer formed at Au(1 1 1) by 2-mercaptobenzimidazole (MBI) under potential control has been based on electrochemical data (charge measurements) and spectroscopic information from the subtractively normalized interfacial Fourier transform infrared spectroscopy method (SNIFTIRS). From the quantitative analysis of the SNIFTIR spectra, a surface coverage Γ/ Γ max was extracted for each sample potential. The evolution of the coverage with potential was in full agreement with the charge density curve. The shift of the pzc in the presence of MBI indicates that the adsorbed molecules have a nonzero component of the permanent dipole moment in the direction perpendicular to the electrode surface. Thanks to the high quality of the spectra, it was possible to determine the orientation of MBI molecules at the surface in the monolayer and submonolayer range. The angle between the C 2-axis of the molecule and the direction normal to the surface is close to 64 ± 4° and its small change (<15°) with potential indicates that the orientation of the molecules is chiefly controlled by the chemical interaction between the sulphur atom and the gold surface.

Quantitative analysis of monomer vapor release from two‐solution bone cement by using a novel FTIR technique

Methyl methacrylate monomer can evaporate from bone cement to reach cytotoxic levels of concentrations in the implant bed of total joint prosthesis. Therefore, this study was performed by using a novel Fourier transform infrared spectroscopy method to quantify the release of monomer vapor from experimental two-solution bone cement in vitro during polymerization, to examine the effect of surface area versus cement mass, and to explore the effect of initiation chemistry. The results revealed that monomer vapor release is a surface phenomenon. In addition, initiation chemistry plays a major role in controlling the reaction time, and therefore heat concentration and dissipation, which resulted in a higher absorbance peak as initiation chemicals concentration increased. It was concluded that using the FTIR to monitor MMA vapors is an effective technique to obtain quantitative information about monomer vapor release from bone cements during polymerization and provides insight on the polymerization kinetics of two-solution acrylic bone cement.

Infrared spectroscopy method reveals hydrogen bonding and intermolecular interaction between components in polymer blends

AbstractAn infrared spectroscopy method was devised to uncover evidence of hydrogen bonding and intermolecular interaction between components in solid poly(lactic acid) (PLA) and poly(hydroxyester ether) (PHEE) blends. The method compares Gaussian/Lorentzian deconvoluted infrared spectra of the polymer blends with deconvoluted spectra of weight ratio‐equivalent mixtures of the physically separated polymers. Infrared spectra of polymer blends, where hydrogen bonding exists, differ from spectra of physical mixtures of the polymers. Deconvoluting spectra of the blends into their underlying peaks revealed theoretically expected differences between hydrogen‐bonded and nonhydrogen bonded components. The findings are supported by differential scanning calorimetry, scanning electron microscopy, and mechanical rheometry studies. The new method, differential spectral deconvolution, afforded a quantitative estimate of the extent of hydrogen bonding between PLA and PHEE and could therefore be used to measure the degree of interaction between components in thermoplastic blends. This technique is superior to conventional spectral subtraction and it should be applicable to intimate mixtures or solid solutions in general. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 813–821, 2005

Alkali-silica reactivity criteria for concrete aggregates

In this study, the suitability of the threshold alkali level, TAL, the kinetic parameter, In k, and the microstructural disorder coefficient, Cd, of the aggregates, taken as alkali-silica reactivity criteria, was assessed using different typologies of Italian natural ASR-susceptible aggregates of known field performance. The TAL, In k, and Cd were determined using a modified version of the RILEM AAR-3 concrete prism expansion test, the ASTM C1260 mortar-bar expansion test, and the infrared spectroscopy test, respectively. It was found that the three reactivity criteria are all appropriate for discriminating between reactive and innocuous aggregates. However, the TAL proves to be a more suitable criterion for interpreting the field performance data of the aggregates investigated. There exists a linear relationship between TAL and In k, or between TAL and Cd, which provides a rapid means of estimating the threshold alkali levels of ASR-susceptible aggregates from the results of the ultra-accelerated mortar-bar test and/or the infrared spectroscopy test. A TAL-based classification of the degree of reactivity of the aggregates, as well as some modifications of the reactivity domains established by the infrared spectroscopy method are also proposed.

Quantification of alcohol in beverages by density and infrared spectroscopy methods

The amount of ethanol in beverages has been quantified by density and infrared spectroscopy methods. The density method allows only the amount of ethanol to be quantified, while the infrared spectroscopy method allows the quantification of ethanol and, if any, the presence of contaminants such as methanol. The amount of ethanol quantified agrees to bottle declaration particularly for the infrared spectroscopy method. The infrared spectroscopy method coupled with a mathematical treatment (PCA and PLS-2) thus distinguishes itself as a fast and reliable technique for determining the amount of ethanol in beverages.