Attenuated Total Reflection Technique Research Articles

Using Attenuated Total Reflection (ATR) Apparatus to Investigate the Temperature Dependent Dielectric Properties of Water, Ice, and Tissue-Representative Fats

A novel method of investigating the temperature dependent variation of aspects of the complex refractive index n* in samples in the THz range using continuous, non-polarised, synchrotron radiation is presented. The method relies on the use of ATR apparatus, and retains the advantage of minimal sample preparation, which is a feature of ATR techniques. The method demonstrates a “proof of concept” of monitoring temperature reflectance whilst continuously heating or cooling samples by using a temperature variable Thermal Sample Stage. The method remains useful when the refractive index of the sample precludes attenuated total reflection study. This is demonstrated with the water reflectance experiments. The temperature dependent ATR reflectance of tissue-representative fats (lard and Lurpak® butter) was investigated with the novel approach. Both are within the ATR range of the diamond crystal in a “true” ATR mode. Lard showed no clear temperature variation between −15 °C and 24 °C at 0.7 to 1.15 THz or 1.70 to 2.25 THz. Lard can be regarded as having invariable, constant, dielectric properties within mixtures when biological substances are being assessed for temperature dependent dielectric variation within the stated THz ranges. Lurpak® butter (water content 14.7%) displayed temperature dependent reflected signal intensity features with a steady decline in reflectivity with increasing temperature. This is in line with the temperature-dependent behaviour of liquid water. There is no rapid change in reflected signal intensity even at −20 °C, suggesting that emulsified water retains liquid-water-like THz properties at freezing temperatures.

Using Coffee Pulp as Bioadsorbent for the Removal of Manganese (Mn (II)) from Synthetic Wastewater

This research focuses on the removal of contaminants from wastewaters as a matter of great interest in the field of water pollution. The first decades of the 21st century have brought numerous approaches for the development of cheaper and more effective adsorbents capable of eliminating heavy metals. The study aims to examine the way coffee pulp (Castilla variety from Caldas, Colombia) was used as a bioadsorbent for the removal of Mn (II) from synthetic wastewater to fulfill goals 3 and 6 proposed in the Sustainable Development Goals stated for the 2030 Agenda, particularly in Sections 3.9 and 6.9. In order to achieve this objective, the agricultural residue was subjected to bromatological characterization, determination of the lignocellulosic composition, and identification of characteristic organic functional groups through IR spectrophotometry, using the ATR (attenuated total reflection) technique. Additionally, the optimal parameters for contaminant removal were identified, regarding the biomass quantity, the optimum pH, the stirring time, the adsorption kinetics, the zero charge potential (pHpzc), the adsorption isotherms, and the explanation of the possible adsorption mechanisms between the contaminant, the surface of the coffee pulp, and the capacity of maximum adsorption. The results show that lignocellulosic material presented a cellulose content of 29.93 ± 0.21% and a lignin content of 19.25 ± 0.16%. The optimum parameters found were as follows: Particle size of 180 µm, contact time from 90 min to 100 RPM, optimum pH of 4.0 pH units, room temperature; the kinetic model adjusted to the bioadsorption process was Ho and McKay’s pseudo-second-order, under an isotherm of the Langmuir model, for which the removal presented was 53.40%, with a maximum adsorption capacity of 8.01 mg·g−1. Finally, the novelty of the reported research consists of using coffee pulp as a bioadsorbent without chemical modification, for the removal of heavy metals, in this case Mn (II), in industrial wastewater, which would be another application of this coffee by-product.

Development of Novel Glucose oxidase Immobilization on Graphene/Gold nanoparticles/Poly Neutral red modified electrode

Abstract Glucose oxidase (GOx) was immobilized onto glassy carbon electrode (GCE) that modified by reduced graphene oxide-gold nanoparticles- poly neutral red (RGO/AuNPs/PNR) nanocomposite. The composite was analyzed by scanning electron microscope (SEM), energy dispersive x-ray (EDX) spectroscopy, atomic force microscopy (AFM), attenuated total reflectance (ATR), cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). SEM/EDX analysis showed the morphological of the nanocomposite. AFM results showed the morphology and structure of the RGO/AuNPs and RGO surfaces. The covalent bonding between glucose oxidase and composite was confirmed by ATR technique. The electrochemical experiments were done in 100 mM phosphate buffer at pH 7 and temperature of 25 °C with three electrodes including Ag/AgCl, platinum wire and the modified GCE as the reference electrode, the auxiliary electrode and working electrode respectively. The electrochemical results confirmed the activity and direct electron transfer of immobilized enzyme. The immobilized electroactive GOx concentration was estimated 3.06 × 10−11 mol cm−2. The results showed the immobilized enzyme had a good stability and maintained 90% of its performance after two weeks. The nanocomposite bioanode in an air-birthing biofuel cell and 100 mM glucose concentration showed 176 μWcm−2 Power density. This strategy could be used for GOx-based biofuel cells.

Application of ATR-FTIR analysis for determination of fumonisins in corn

In order to develop rapid, inexpensive and, at the same time, reliable method for the analysis of molds of the genus Fusarium as an indicator of the presence of fumonisins in corn samples, possible application of Fourier transform infrared spectroscopy (FTIR) with attenuated total reflection (ATR) technique was examined. The content of fumonisins in contaminated corn samples had previously been quantified by ELISA method. At the spectrum of the sample contaminated with a high concentration of mycotoxins, there was a lack of the peak at 1,743 cm-1, but the peak was observed at 1709 cm-1. To the purpose of result classification the principal component analysis (PCA) and cluster analysis were applied. Conclusions of the two methods were similar both when applying ATR technique in the whole region of the spectrum (1,150-1,770 cm-1) and when the whole spectrum was divided into two regions: 1,150-1,450 and 1,450-1,770 cm-1. However, classification of samples was somewhat better in the ranges 1,150-1,770 and 1,450-1,770 cm-1 . Of the 16 analyzed corn samples, only very contaminated corn sample with 190 mg/kg was correctly classified as compared to the other samples with the content of less than 10 mg/kg. Also, it was found-passing recording of spectra of contaminated corn of the same genotype in order to avoid the possible impact of different hybrids on the spectrum.

Phospholipid-protein balance in affective disorders: Analysis of human blood serum using Raman and FTIR spectroscopy. A pilot study

Raman and FTIR (Fourier Transform Infra Red) spectroscopies provide information on the chemical structure of compounds through identification and analysis of functional groups. In the present study, both spectroscopic techniques were used for investigating the phospholipid – protein balance in blood serum of depressed subjects (major depressive disorder and bipolar disorder type I or II) taking also into account their age and gender. The obtained results were compared with those of healthy subjects. The Raman and FTIR (using ATR (Attenuated Total Reflectance) technique), spectra show that a correlation between the level of phospholipids and proteins exists. Indeed, in depressed subjects the quantity of phospholipids and proteins is lower, compared to healthy ones. The second derivative of FTIR spectra shows that phospholipids directly affect the structure of proteins and their functions. In all male depressed subjects a higher amount of phospholipids and proteins compared to female depressed subjects was measured, offering them faster recovery perspectives. Spectroscopy results show that the phospholipids’ and proteins’ levels are lower in depressed subjects from 41 to 65 compared to the age group between 20 and 40, independently from the gender. Consequently, this study shows that Raman and infrared spectroscopies might be applied as a diagnostic tool to evaluate the balance between phospholipids and proteins in blood serum as a potential biomarker in depressive disorders.

Does sample drying temperature affect the molecular characteristics of organic matter in soil and litter? A statistical proof using ATR infrared spectra

At each step of sample handling and pretreatment it is important to consider potential effects on the result of the analysis. Sample drying is a basic procedure in sample preparation for many analyses. In practice, different sample drying procedures (e.g. freeze drying, air drying, or drying at different temperatures up to 105°C) may be used prior to perform attenuated total reflection (ATR) spectroscopy, but the effect of sample drying temperature is rarely assessed. The latter technique was used to test the influence of sample drying treatment on the molecular characteristics of six contrasting substrates which are common in soil science (two mineral soils, two organic soils and two foliar litter samples). We compared the mid-infrared ATR spectra of the samples after freeze-drying, as well as oven-drying at 60 and 105°C, respectively. Our results demonstrate a significant absence of any detectable influence of sample drying on the spectra of the six substrates under study, and hence on parameters which are reflected in the spectra. Accepting null hypothesis of no effect is linked to a risk of the second kind (β). Calculation of β needs a proper design of the experiment (DoE). By means of this DoE, the result is significant on a 5% level. In previous studies where drying temperature had influenced organic matter composition, either (1) labile compounds in fresh organic materials were under investigation, or (2) parameters were investigated which cannot be detected by using the ATR technique. Our results indicate that in the context of soil organic matter – where fresh materials containing labile compounds are of minor interest − the drying conditions do not affect the determination of parameters, which can be studied by means of the ATR technique.

A Tape Method for Fast Characterization and Identification of Active Pharmaceutical Ingredients in the 2-18 THz Spectral Range

In order to find counterfeit drugs quickly and reliably, we have developed ‘tape method’ a transmission spectroscopic terahertz (THz) measurement technique and compared it with a standard attenuated total reflection (ATR) THz spectroscopic measurement. We used well-known training samples, which include commercial paracetamol and aspirin tablets to check the validity of these two measurement techniques. In this study, the spectral features of some active pharmaceutical ingredients (APIs), such as aspirin and paracetamol are characterized for identification purpose. This work covers a wide THz spectral range namely, 2-18 THz. This proposed simple but novel technique, the tape method, was used for characterizing API and identifying their presence in their dosage forms. By comparing the spectra of the APIs to their dosage forms (powder samples), all distinct fingerprints present in the APIs are also present in their respective dosage forms. The positions of the spectral features obtained with the ATR techniques were akin to that obtained from the tape method. The ATR and the tape method therefore, complement each other. The presence of distinct fingerprints in this spectral range has highlighted the possibility of developing fast THz sensors for the screening of pharmaceuticals. It is worth noting that, the ATR method is applicable to flat faced tablets whereas the tape method is suitable for powders in general (e.g. curved surface tablets that require milling before measurement). Finally, we have demonstrated that ATR techniques can be used to screen counterfeit antimalarial tablets.

In-Line Monitoring of Bacteria in Drinking Water By Infrared Spectroscopy and Micro-Flow Cytometry

Water from a municipal network water supply is stored in tanks and then pumped to tanks in tall buildings, which is so called “second water supply”. However, the water stored in tanks provides the potential environment for bacteria to grow and multiply. It is labor and time-consuming to routinely and frequently sample water from the water tanks distributed in a city, and to test all samples by biological methods in labs, which thus restricts the detection and prevention of water-borne diseases. Therefore, a rapid and low-cost method1,2 is urgently needed to routinely and automatically monitor and report the bacterial level in water tanks, allowing for taking appropriate actions in time. Infrared (IR) spectroscopy is a powerful tool for characterization and identification of micro-organisms because of its sensitivity and specificity, speed, and potential for automation. Microorganisms have unique “fingerprint” spectral features in the mid-infrared (MIR) range. Therefore, IR spectroscopy is a feasible technique for the identification of unknown bacterial samples based on the pre-established bacterial spectrum libraries. There are mainly two modes in IR spectroscopy to obtain the IR spectrum of bacteria in water - attenuated total reflection (ATR) and transmission modes. The first mode has been used by many researchers previously because it could avoid the influence of water on the bacterial spectrum, which has three strong absorption bands in the range of 400 to 4000 cm-1. However, the ATR technique lacks the ability to provide spectral data for quantitative analysis because the spectrum acquired in ATR mode is dependent on the thickness and density of the bacterial film formed on the outer surfaces of the ATR crystal. Therefore the transmission mode of FTIR is used in this research. Three strains of two species, E.coli K-12 MG1655 and E.coli K-12 HS2210 from Ecoli and Staphylococcus aureus (ATCC 25923) were placed directly into double distilled water. Then, the CaF2 cuvette containing bacteria suspention with different concentrations were used to obtain the IR spectra using a Vertex v80 FTIR spectrometer. Ultra-high concentrations of bacteria over 1010 cells/ml are used to guarantee enough changes in absorption between double distilled water and samples. Time-resoved IR spectra of E.coli K-12 MG1655 shows that its spectrum varies slightly within one hour. Obvious differences were observed in the spectra of E.coli K-12 MG1655 and Staphylococcus aureus (ATCC 25923), which shows the specificity on the IR spectrum of different species. However, similar differences were not found between E.coli K-12 MG1655 and HS2210. In addition, the intensity of the absorption peaks in the spectra of all the three strains is proportional to the concentration of the samples.Because of limitation of FTIR spectroscopy on quantifying bacteria accurately, a photonic-microfluidic integrated device based flow cytometer3-5 is incorporated into the monitoring system to ensure reliable estimation of bacterial concentration. The functionality layer of the device including input and output waveguides, lens systems and microfluidic channels is fabricated by patterning SU-8 photoresist using photolithography, which is actually supported by a pyrex glass substrate and covered by a PDMS covering layer with holes aligned with all the inlets and outlet. Light from a laser is directed into the input waveguide of the device through an optic fiber, then focused to the center of the microfluidic channel by a lens system, where the bacteria will be interrogated. Bacterial suspension in a syringe is injected to the sample inlet by a syringe pump and hydro-focused into the center of microfluidic channel by the sheath flows at both sides. Scattered light produced by bacteria passing through the focused light beam will be collected by the objective and filtered by an optic filter with passband of 525-535 nm. A photomultiplier tube is used to detect, convert and amplify the light signals into current signals, which will be further amplified into votage singals by a current to voltage amplifier. Voltages signals will be digitized by a data acqusition card and recorded by a custom LabView program for data analysis.The performance of flow cytometer based on the integrated devices with different beam shaping lens systems was calibrated by detecting scattered light from 1µm-diameter blank polystyrene beads running through the device. Due to uniform geometry, size and material, the device yielding minimal coefficient of variation (CV) will be the best for applications.Enumeration of E.coli in phosphate-buffered saline was carried out to validate the accuracy of counting bacteria using this micro-chip based flow cytometer. A 92% of detection efficiency was achieved. Expanded population of distribution of E. coli counting than beads counting was found because of the more flexibility of scattering light by rod-shape of E.coli than sphere-shape of beads as well as the natural size variation of E. coli. Tests on mixture of E.coli and 2µm, 4 µm beads show distinct separation of the population distribution, confirming the ability to differentiate E.coli from larger size inorganic particles by scattering intensity.

Comparison of transmission FTIR, ATR, and DRIFT spectra: implications for assessment of bone bioapatite diagenesis

Evaluation of diagenesis in bioapatite samples is an important step for screening bone and tooth samples for stable isotope analysis to ensure in vivo signatures are obtained. Fourier transform infrared (FTIR) spectroscopy is one tool used to evaluate diagenesis by anthropological geochemists and commonly employs calculating the infrared splitting factor (IR-SF) and carbonate-to-phosphate ratio (C/P). There are three commonly used sample preparation techniques for vibrational spectroscopy: transmission FTIR, attenuated total reflection (ATR), and diffuse reflectance infrared Fourier transform (DRIFT). Each technique characterizes the internal vibrations of particular molecular groups, such as carbonate (CO3) and phosphate (PO4), using different optical properties to detect absorbance bands. Spectra are correlated between techniques using correction equations that account for differences in optical properties. Traditionally, anthropologists have used spectra produced by transmission FTIR to assess diagenesis, most commonly using two indices (IR-SF and C/P); however, recently the ATR and DRIFT techniques have been used as an alternative to transmission FTIR. The spectra produced by the three techniques are thought to be interchangeable in calculating the indices used to assess diagenesis. In this study, we evaluated the interchangeability of the three FTIR techniques by analyzing 452 prehistoric and modern bioapatite samples. Results indicate that IR-SF and C/P values are not equivalent between the three techniques. However, ATR produced more reliable results and was comparable to transmission FTIR. The DRIFT method showed much lower resolution, and did not distinguish between modern and prehistoric bioapatite samples as clearly.

Vibrational and theoretical study of selected diacetylenes

Six commonly used disubstituted diacetylenes with short side-chains (RCCCCR, where R=CH2OH, CH2OPh, C(CH3)2OH, C(CH3)3, Si(CH3)3, and Ph) were analyzed using vibrational spectroscopy and quantum-chemical calculations to shed new light on structural and spectroscopic properties of these compounds. Prior to that the conformational analysis of diacetylenes was performed to search the Potential Energy Surface for low-energy minima. Theoretical investigations were followed by the potential energy distribution (PED) analysis to gain deeper insight into FT-Raman and FT-IR spectra that, in some cases, were recorded for the first time for the studied compounds. The analysis was focused mainly on spectral features of the diacetylene system sensitive to the substitution. Shifts of the characteristic bands and changes in bond lengths were observed when changing the substituent. Furthermore, Fermi resonance was observed in the vibrational spectra of some diacetylenes. FT-IR spectra were measured by using two methods, i.e. transmission (with KBr substrate) and Attenuated Total Reflection (ATR), showing the latter adequate and fast tool for IR measurements of diacetylenes. Additionally, Surface Enhanced Raman Spectroscopy (SERS) was applied for phenyl derivative for the first time to study its interaction with metallic nanoparticles that seems to be perpendicular.

Fourier Transform Infrared Radiation Spectroscopy Applied for Wood Rot Decay and Mould Fungi Growth Detection

Material characterization may be carried out by the attenuated total reflectance (ATR) Fourier transform infrared (FTIR) radiation spectroscopical technique, which represents a powerful experimental tool. The ATR technique may be applied on both solid state materials, liquids, and gases with none or only minor sample preparations, also including materials which are nontransparent to IR radiation. This facilitation is made possible by pressing the sample directly onto various crystals, for example, diamond, with high refractive indices, in a special reflectance setup. Thus ATR saves time and enables the study of materials in a pristine condition, that is, the comprehensive sample preparation by pressing thin KBr pellets in traditional FTIR transmittance spectroscopy is hence avoided. Materials and their ageing processes, both ageing by natural and accelerated climate exposure, decomposition and formation of chemical bonds and products, may be studied in an ATR-FTIR analysis. In this work, the ATR-FTIR technique is utilized to detect wood rot decay and mould fungi growth on various building material substrates. An experimental challenge and aim is to be able to detect the wood rot decay and mould fungi growth at early stages when it is barely visible to the naked eye. Another goal is to be able to distinguish between various species of fungi and wood rot.

Investigations of Accelerated Climate Aged Wood Substrates by Fourier Transform Infrared Material Characterization

Fourier transform infrared (FTIR) material characterization by applying the attenuated total reflectance (ATR) experimental technique represents a powerful measurement tool. The ATR technique may be applied on both solid state materials, liquids and gases with none or only minor sample preparations, also including materials which are nontransparent to infrared radiation. This facilitation is made possible by pressing the sample directly onto various crystals, for example, diamond, with high refractive indices, in a special reflectance setup. Materials undergoing ageing processes by natural and accelerated climate exposure, decomposition and formation of chemical bonds and products, may be studied in an ATR-FTIR analysis. In this work, the ATR-FTIR technique is utilized to detect changes in selected wood building material substrates subjected to accelerated climate exposure conditions. Changes in specific FTIR absorbance peaks are designated to different wood deterioration processes. One aim is by ATR-FTIR analysis to be able to quantitatively determine the length of the wood ageing time before priming/treatment. Climate parameters like temperature (including freezing/thawing), relative air humidity, wind driven rain amount, solar and/or ultraviolet radiation, and exposure duration may be controlled in different climate ageing apparatuses. Both impregnated and raw wood samples have been employed in the experimental investigations.

Real-Time Spectroscopic Analysis of Extracellular Matrix Produced by MC3T3-E1 Preosteoblastic Cells Cultured under Dynamic Conditions

The deposition of extracellular matrix (ECM) produced by osteoblasts is one of the first steps in bone formation. Composition and structure of the ECM influence the development and strength of bone, as well as the onset of its mineralization. Since ECM is secreted onto the surface where the cells attach, Fourier transform infrared (FT-IR) attenuated total reflection (ATR), as a surface sensitive technique, provides a useful tool for its investigation, as ECM instead of the cells is predominantly detected by the IR beam. The purpose of the present study was to develop the FT-IR ATR technique so that real-time measurements of the ECM produced by MC3T3-E1 osteoblasts could be obtained in situ. Measurements were performed using polarized incident IR light to apply a procedure for solvent compensation which reduces the influence of culture medium on the evaluation of the amide I and II bands. The formation of ECM took place in a flow-through chamber under dynamic conditions by applying a constant flow of culture medium and was tracked over a time period of two weeks by evaluation of the integrated absorbance of amide I and II bands reflecting the amount and isotropic arrangement of amide bonds in the ECM. Cultures without ascorbic acid had a reduced protein concentration that enabled the analysis of cell-mediated matrix accumulation. Presence and proliferation of cells after two weeks of permanent flow-through of culture medium was shown by cell counting exhibiting a 67% increase in cell number as well as by crystal violet and live/dead staining. These results demonstrate the application of FT-IR ATR spectroscopy for monitoring matrix formation.

An Optical Fiber Sensor for Measuring Light Absorption in Suspension Solutions

An optical fiber sensor based on attenuated total reflectance (ATR) for extraction chemical information from highly scattering turbid materials has been evaluated. The influence of particles on bulk absorption and ATR transmitted spectra of micron-sized graphite flakes and spherical glassy carbon suspensions were investigated. The ATR transmitted spectra of coiled fiber-optic sensor in those suspensions with various concentrations are insensitive to scattering of suspended particles, especially for graphite flake suspensions. The reason for different influence of graphite flakes and spherical glassy carbon particles suspensions on e ATR spectra analyzed. This study demonstrates that fiber-optic sensor based on ATR technique is a feasible technique in application for monitoring turbid suspensions.

Comparison of infrared attenuated total reflection and Raman spectroscopy in the quantitative analysis of diclofenac sodium in tablets

The quantification of diclofenac sodium (DS) in tablets was performed using partial least squares (PLS) models based on FTIR ATR (Fourier transform infrared attenuated total reflection) and FT-Raman spectra. Separate calibration models were built for two groups of tablets, standard and sustained release, containing different excipients. To compare the predictive ability of these models the relative standard errors of prediction (RSEP) were calculated. In the case of DS determination from the Raman data, RSEP error values in the range of 2.4–2.8% (2.7–2.9%) for the calibration (validation) data sets were obtained. For ATR models constructed using spectra registered three times for each sample, RSEP errors in the range of 3.6–3.7% (4.2–4.3%) were found. These errors decreased to 2.8% (3.0%) when spectra collected six times were applied. Five commercial products containing 25, 50, 75 and 100 mg of DS per tablet were quantified. Concentrations derived from the elaborated models correlated strongly with the results of reference analyses and gave recoveries of 99.1–101.3% and 99.1–101.7% for the ATR and Raman data, respectively. Although both spectroscopic techniques can be used as fast and convenient alternatives to the standard pharmacopeial methods of DS quantification in solid dosage forms, in the case of the ATR technique, it is necessary to repeat measurements at least a few times to obtain acceptable quantification errors.

Grading of intrinsic and acquired cisplatin-resistant human melanoma cell lines: an infrared ATR study

Attenuated total reflection (ATR) spectroscopy is used as an in vitro optical approach for the diagnosis and characterization of cell and tissue pathology. In comparison with the more conventional FTIR microspectroscopy that relies on transmission of IR radiation, ATR spectroscopy uses the evanescent wave technique, which is a step forward toward in vivo research. The aim of the present investigation was to examine the potential of ATR spectroscopy to differentiate between drug-resistant and drug-sensitive melanoma cell lines. We studied two human melanoma parental cell lines, GA and BG, and their cisplatin-resistant counterparts, GAC and BGC, respectively, which were derived by survival selection with this anticancer drug. Cisplatin cytotoxicity was measured on the four cell lines, and their relative resistance to cisplatin was established: BGC > BG > GAC > GA. Different resistance mechanisms were noticed between the two parental groups in accordance with their spectrum. ATR spectra-based cluster analysis of the selective biomarkers, such as phosphate and RNA/DNA, were found useful in differentiating sensitive from resistant cells. Normalized and absolute values of the differences between spectra were employed to compare between the two parental groups. It was possible to predict the relative cisplatin resistance between the cell lines using the discriminant classifying function. The success rates in predicting cisplatin resistance in these cells was 88 and 81% for GA versus GAC and BG versus BGC, respectively. These results support the further development of the ATR technique as a simple, in vitro, reagent-free method to identify drug resistance in cancer cells.

Solution casting, characterization, and performance evaluation of perfluorosulfonic sodium type membranes for chlor‐alkali application

AbstractThis investigation describes solution casting, characterization and performance evaluation of perfluorosulfonic sodium (PFSS) type membranes prepared by three different methods from Nafion solution and Nafion‐117 for Chlor‐Alkali (CA) application. A Chlor‐Alkali experimental set‐up was designed and constructed for performance evaluation of the recast membranes. The chemical structure of solution cast films was studied and confirmed by FTIR (Fourier Transform infrared spectroscopy) and ATR (Attenuated total reflection) techniques. The physical properties of solution cast films including mechanical strength, thermal behavior, water sorption, ion‐exchange capacity (IEC), morphology, and crystallinity were also evaluated. All the recast polymeric films behave like elastomers with low modulus but high elongation at break. Differential scanning calorimetric (DSC) thermograms of solution cast films showed two endothermic peaks at 180°C and 250°C attributed to matrix glass transition (Tgm) and ionic cluster glass transition (Tgc) of the Nafion polymer, respectively. The water uptake of polymeric films was reasonable in comparison with Nafion‐117. Solution casting has no significant effect on ion exchange capacity of the recast films. The scanning electron microscope (SEM) micrograph showed that the morphology of recast films is reasonably similar with Nafion‐117. However, the as‐cast films have some micro pores, which are produced during solution casting. The crystallinity of annealed film, because of the heat treatment was slightly high due to local ordering. According to the experimental results, which obtained from performance evaluation in CA cell, the properties of recycled films are similar to commercial membranes such as Nafion‐117 and can be used in CA process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Isotope effects in liquid water by infrared spectroscopy. III. H2O and D2O spectra from 6000tocm−1

The infrared spectra (IR) of pure liquid light (H(2)O) and heavy (D(2)O) water were obtained with attenuated total reflection (ATR) and transmission measurements in the mid-IR and far-IR. With these and with other values obtained from the literature, the real (n) and imaginary parts (k) of the refractive index were meticulously derived in the complete IR region from 6000 to 0 cm(-1). The reliability of the results resides in the critical comparison of our experimental data with that obtained from other laboratories and between calculated and experimental spectra, obtained by ATR and transmission techniques. The new optical properties (n and k) can now be used as standards for liquid H(2)O and D(2)O. To these we have added the water (H and D) absorption coefficients (K) that are derived from the k values. These can be used as references for spectra obtained by transmission with an absorbance intensity scale because they are almost the same.

Theoretical Treatment of Particle-Size Measurements by Applying Attenuated-Total-Reflection Technique and Its Comparisons with Experimental Results

Theoretical equations for a particle size-determination method by applying an attenuated-total-reflection (ATR) technique were obtained. Based on these equations, the ATR-spectral intensities were calculated as functions of the sample amount and on the particle size for various choices of the experimental parameters. A mono layer region was more adequate for size measurements than a multiple-layers region. A prism and the incidence angle should be adequately selected according to the aims of the measurements. Experimental results of the sample amount dependences of the spectral intensities were almost consistent with calculations. The experimental results of size dependences showed the same tendency as those by calculations for SiO2 and SiC; especially for SiC, they were in just accord with those by calculations in the case of a KBr prism. Each component of a mixed plural-kind-particles sample almost agreed in its spectral intensity with that of a corresponding single-kind-particles sample. The particle size-determination method, based on the ATR technique, was theoretically supported, and its characteristics were revealed.

Infrared Analysis of Urinary Stones, Using a Single Reflection Accessory and a KBr Pellet Transmission*

This work is a comparative study of two FTIR techniques applied to urinary stones analysis: single reflection diamond attenuated total reflection (ATR) and KBr pellet transmission (KPT). We show that the two methods allow the identification of all stone components. The ATR technique is more useful and rapid to identify the species without sample pretreatment. Nevertheless, KPT is more appropriate for components determination in urinary stones. These techniques were applied to the study of a series of 313 calculi. The stone constituents were first identified by ATR, and in a second step, the proportion of each species present in the stone was determined by KPT in whole‐stone mixture. The results obtained showed the presence of 11 different components classified as follows with the frequency of detection in the stones studied: calcium oxalate monohydrate (whewellite), 78.9%; carbapatite, 33.9%; calcium oxalate dihydrate (weddellite), 24%; uric acid anhydrous, 19.2%; ammonium hydrogen urate, 7%; struvite, 4.8%; cystine, 1%; ammonium sodium urate and other phosphates (amorphous carbonated calcium phosphate, brushite, whitlockite), each in less than 1%.