Abstract: Methodologies based on vibrational spectroscopies (FT-Raman and FT-Infrared) and powder X-ray diffraction (PXRD) were developed for the characterization of mixtures consisting of four calcium phosphate phases that might be found in mineralized tissues or implant materials: hydroxyapatite (HAP), octacalcium phosphate (OCP), dicalcium phosphate dihydrate (DCPD) and dicalcium phosphate anhydrous (DCPA). No single technique was sufficient for the analysis of the quaternary mixture. Characterization of such solids was possible by: (a) combination of Infrared (IR) and Raman spectroscopic analysis, (b) combination of IR and PXRD data, and (c) combination of PXRD patterns recorded before and after heating the mixture of calcium phosphates at 850 degrees C. Proposed methods were evaluated by establishing the respective detection limits. It was found that the method using the data from the PXRD patterns recorded before and after the heating of the solid mixture has yielded the lower detection limits. (C) 2012 Elsevier B.V. All rights reserved.
Abstract: Fractures are the most frequent health problem associated with bone. Metabolic diseases, such as osteoporosis, affect skeletal integrity, reduce strength and toughness of bone and lead to increased risk of fragility. In the present work, structural changes of bone were studied on osteoporotic tibiae from female wistar rats compared to healthy controls. Osteoporosis was induced through ovariectomy. Bone composition and quality was evaluated employing Raman spectroscopy. The heights of the primary phosphate band (PO43-, v(1)) at 959 cm(-1) and 1072 cm(-1) for the carbonate of the mineral, the matrix bands at 855 cm(-1) (proline), 877 cm(-1) (hydroxyproline) and 922 cm-1 (proline), as well as the major sub-bands under amide I envelope (1590-1710 cm(-1)) were measured. The mineral to matrix ratio [959 cm(-1)/(855 cm(-1) + 877 cm(-1) + 922 cm(-1))] was reduced, suggesting decreased mineral quantity in the osteoporotic tibiae compared to controls. The carbonate to phosphate ratio [1072 cm(-1)/959 cm(-1)] land mineral crystallinity were found to increase. Band changes of the amide I envelope were attributed to alteration of collagen cross-linking which was found to accompany the increased fragmentation and removal of the fibers. It was, thus, concluded that severe deterioration of collagen network takes place following disease as it not only lessens but it loses its elasticity as well. (C) 2012 Elsevier B.V. All rights reserved.
Abstract: A new non-destructive method was applied in order to assess bone integrity. The method is based on measurement
of bone dynamic characteristics (MDF and QF) by applying vibration excitation in the range of acoustic frequencies,
in the form of an acoustic sweep signal. The method has been already applied on metallic structures and composites,
including animal bones and has shown the potential to become a valuable assessment tool for monitoring bone
structural changes. The measured characteristics are directly related with stress concentration due to discontinuities in
the material of the bone, such as changes in porosity due to osteopenia. In turn, stress concentration is known to cause
fracture in such materials. In this work, sheep femora were split in cuts and tested to detect changes in MDF - QF, BMD
(kg/m2
), RS and IEF, without the effect of soft tissue. MDF - QF are shown to be the best indicators and measures of
the tendency of the bone to fracture, as compared to the conventional methods (BMD and RS) and to the absolute
strength measure (IEF).
Abstract: In several bone deproteination protocols the chemical agent used for protein cleavage is hydrazine. The effect of hydrazine deproteination method on the crystal size and crystallinity of the bone mineral was studied. Bovine bones were subjected to this protocol and the crystal size and crystallinity of the remaining bone mineral were determined by X-ray Diffraction (XRD), by measuring the width at the half of the maximum intensity of the (002) reflection. It was found that hydrazine deproteination induces noteworthy increase of crystal size and crystallinity. The effect was enhanced by increasing hydrazine temperature from 25 to 55°C. Furthermore, infrared spectroscopy revealed that hydrazine facilitates the removal of carbonate and acid phosphate ions from bone mineral. It is proposed that the mechanism of modification of crystal size and crystallinity lies on the removal of these ions thus, resulting in crystal re-organization.
Abstract: In the present work we have investigated the influence of the preparation method on the physicochemical and activity features of CoOx/gamma-Al2O3 catalysts used for the combustion of anode tail gas produced in a proton-exchange membrane (PEM) fuel cell. The catalysts prepared contain 21% (w/w) Co and have been calcined at 850 degrees C. Three different impregnation methodologies have been followed: incipient wetness impregnation (IWI) using a cobalt nitrate aqueous solution, incipient wetness impregnation using a mixed cobalt nitrate-nitrilotriacetic acid (IWI-nta) aqueous solution and equilibrium deposition filtration (EDF) using a cobalt nitrate aqueous solution. The catalysts were characterized using nitrogen adsorption for determining the specific surface area, the pore volume and the mean pore diameter as well as using X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS; UV-vis), LRS, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR). Catalytic activity measurements were performed in the temperature range 250-850 degrees C using a continuous flow fixed-bed micro-reactor working under atmospheric pressure and fed with a reaction mixture consisted of 15% H-2/3% CO/1.1% CH4/20% O-2 balanced in He. The EDF methodology imposed interfacial deposition and resulted to the formation of an almost bi-dimensional surface precipitate. Upon calcination, this surface precipitate provided a very well-dispersed CoOx amorphous species strongly interacted with the support surface and thus hardly reducible as well as relatively small Co3O4 Supported nanocrystals (14.3 nm). The first phase is the predominant one. Therefore, EDF resulted to a catalyst with the highest cobalt surface and specific surface area. The conventional IWI imposed bulk (solution) precipitation and thus induced relatively large supported crystallites which upon calcination provided relatively large supported Co3O4 nanocrystals (19.8 nm) and CoAl2O4 as well. The formation of the relatively large nanocrystals and the insertion of cobalt inside the gamma-alumina lattice to form CoAl2O4 may be responsible for the lowest cobalt surface obtained in this catalyst. The presence of the nitrilotriacetic acid in the impregnating solution induced the exchange of the water ligands of the Co(II) aqua complex present in the cobalt nitrate solution with organic ligands and thus the bulk precipitation of an organometallic complex. The more bulky organic ligands decreased the cobalt-support interactions. Thus, the insertion of cobalt inside the gamma-alumina lattice and the formation of CoAl2O4 are inhibited upon calcination of the IWI-nta sample. This may be responsible for the relatively higher cobalt surface obtained with respect to that achieved in the IWI sample though the size of the Co3O4 nanocrystals is larger in the IWI-nta sample (25.8 nm). At relatively high reaction temperatures all catalysts exhibited almost the same activity for oxidation reactions. In contrast, at low reaction temperatures the EDF catalyst proved to be more active for the CH4 production as well as for the oxidation of H-2 and CO. This behaviour may be attributed to the favourable physicochemical characteristics of this catalyst. (C) 2008 Elsevier B.V. All rights reserved.
Abstract: A simple, non-destructive, methodology based on FT-Raman spectroscopy was developed for the quantitative analysis of risperidone in commercially available film-coated tablets. A simple linear regression model was constructed based on standard tablets, prepared using the same manufacturing process as the commercially available. The tablets contained 0.27, 0.54, 1.08, 1.62, 2.16, 3.24 and 4.32 wt% risperidone. The most prominent Raman vibration of the active pharmaceutical ingredient at 1533 cm(-1), recorded using a home-made rotating system, was plotted against concentration. The model was tested on commercial film-coated tablets. The results were compared against those obtained by application of HPLC on the same samples.
Abstract: Mesoporous anatase was prepared following sol-gel and using urea as template. The influence of calcination temperature on the phase stability, nanocrystal/aggregate size, pore size distribution and specific surface area as well as on the acid-base behavior in aqueous solutions was studied using X-ray diffraction, laser-Raman and diffuse reflectance spectroscopies, scanning electron microscopy and laser scattering as well as N-2 adsorption-desorption isotherms and potentionnetric mass titrations. The crystal structure was kept constant upon calcination over the whole temperature range, 200-500 degrees C. In this range anatase is constituted from primary nanocrystals. These are assembled into larger, rather spherical, clusters of about 30-40 nm and then into aggregates of various sizes (0.2-0.3 mu m and 2-100 mu m) with a distribution centered at about 12 mu m. Increase of the calcination temperature caused an increase in the size of the primary nanocrystals from 8.1 nm at 200 degrees C to 17.1 nm at 500 degrees C, whereas calcination does not influence the morphology at micro-scale. Moreover, increase of the calcination temperature from 200 degrees C to 500 degrees C brings about a shift in the mean pore diameter from 47 nm to 91 nm accompanied by a decrease in the specific surface area and pore volume. The above effects were related with the aforementioned increase in the size of the primary nanocrystals. The value of pzc and the values of surface charge determined at various pH do not practically depend on the calcination temperature. The absence of pore space confinement effects was explained in terms of the structure and size of the interface development between the anatase surface and the electrolytic solution. (C) 2008 Elsevier B.V. All rights reserved.
Abstract: Atorvastatin calcium (ATC) is the active pharmaceutical ingredient (API) of the best selling lipid-lowering formulation Lipitor. Twelve ATC crystal forms are known and several pharmaceutical companies are developing or have developed generic drug formulations based on different ATC polymorphs. The strong overlap of the X-ray diffraction patterns (XRD) of the polymorphs with the respective patterns of the excipients, the presence of small API quantities in the tablet and the similarity of the crystal phase VIII XRD pattern used in the tablet examined in this work to that of phases IV and IX made identification difficult. Quantitative determination of ATC was attempted using Raman spectroscopy (RS), IR spectroscopy and X-ray powder diffraction. It was found that RS exhibited lower detection limit and a calibration model was constructed. Its application on commercial ATC tablets with 40mg strength yielded an error of 1.25%.
Abstract: Two different nondestructive spectroscopy methods based on near-infrared (NIR) and Fourier transform (FT) Raman spectroscopy were developed for the determination of ticlopidine-hydrochloride (TCL) in pharmaceutical formulations and the results were compared to those obtained by high-performance liquid chromatography (HPLC). An NIR assay was performed by reflectance over the 850-1700 nm region using a partial least squares (PLS) prediction model, while the absolute FT-Raman intensity of TCL's most intense vibration was used for constructing the calibration curve. For both methodologies the spectra were obtained from the as-received film-coated tablets of TCL. The two quantitative techniques were built using five "manual compressed" tablets containing different concentrations and validated by evaluating the calibration model as well as the accuracy and precision. The models were applied to commercial preparations (Ticlid). The results were compared to those obtained from the application of HPLC using the methodology described by "Sanofi Research Department" and were found to be in excellent agreement, proving that NIR, using fiber-optic probes, and FT-Raman spectroscopy can be used for the fast and reliable determination of the major component in pharmaceutical analysis.
Abstract: Raman spectroscopy was applied for the direct non-destructive analysis of amiodarone hydrochloride (ADH), the active ingredient of the liquid formulation Angoron((R)). The FT-Raman spectra were obtained through the un-broken as-received ampoules of Angoron((R)). Using the most intense vibration of the active pharmaceutical ingredient (API) at 1568cm(-1), a calibration model, based on solutions with known concentrations, was developed. The model was applied to the Raman spectra recorded from three as-purchased commercial formulations of Angoron((R)) having nominal strength of 50mgml(-1) ADH. The average value of the API in these samples was found to be 48.56+/-0.64mgml(-1) while the detection limit of the proposed technique was found to be 2.11mgml(-1). The results were compared to those obtained from the application of HPLC using the methodology described in the European Pharmacopoeia and found to be in excellent agreement. The proposed analytical methodology was also validated by evaluating the linearity of the calibration line as well as its accuracy and precision. The main advantage of Raman spectroscopy over HPLC method during routine analysis is that it is considerably faster and no solvent consuming. Furthermore, Raman spectroscopy is non-destructive for the sample. However, the detection limit for Raman spectroscopy is much higher than the corresponding for the HPLC methodology.
Abstract: Identification of the crystal phase of an active pharmaceutical ingredient (API) in a pharmaceutical tablet is of outmost importance since different polymorphs exhibit different physicochemical properties. Furthermore, some of the crystal phases are protected by patents. Identification of Risperidone polymorph A in film coated commercial tablets was attempted using IR spectroscopy, Raman spectroscopy and X-ray powder diffraction (XRPD). The stability of this polymorph through time and during the manufacturing process was also examined. The inability of IR and Raman techniques to identify the presence of polymorph A in the tablets, despite their lower detection limits for Risperidone, left the XRPD as the only technique that could be used for identifying the presence of Risperidone A against the other crystal phases in the presence of the excipients. Polymorph A was proved to be stable during the manufacturing process and after a storage period of 2 years.
Abstract: In a small pilot cell, 16 kg of a Mg-Nd alloy was produced by electrolysis of the raw materials Nd-2(CO3)(3) and MgCO3 dissolved in the molten LiF-NdF3-MgF2 mixture. The anode was constructed with a central opening where the produced gases could escape, setting up a radial liquid flow across the anode, up the central hole and out through two openings through the anode at the interface between the melt and the gas phase. This flow helped to feed the anode with fresh electrolyte. The current efficiency was 87%, and the cathode current density D-c = 3.9 A/cm(2) at 850 degrees C. The electrolyte composition was NdF3(21)-LiF(72)-MgF2(7) mol%. In a lab cell with defined anode area, the limiting anode current density was as low as 0.3 A/cm(2) before the anode effect occurred. The carbonates decomposed to oxides and dissolved much faster than pure oxides as raw materials as shown in solubility studies.
Abstract: The capability of FT-Raman spectroscopy for the fast and non-destructive quantitative analysis of liquid formulations was tested and the results were compared to those obtained by HPLC. Diphenhydramine hydrochloride (DPH), the active ingredient of Benadryl, was determined in the presence of the numerous excipients of the elixir. A Raman calibration model was developed by measuring the peak intensities of different standard solutions of DPH vibration at 1003 cm(-1). Application of the calibration model on the peak intensity recorded from the as-received commercially available sample with 2.5 mg ml(-1) DPH nominal value yielded a value of 2.49+/-0.05 mg ml(-1) DPH. The reliability of this method was verified by testing it against the conventionally used HPLC. The results from both methods were in excellent agreement. The main advantage of Raman over HPLC method during routine analysis is that is considerably faster and less solvent consuming. Furthermore, Raman spectroscopy is non-destructive for the sample. On the other hand, the detection limit for Raman spectroscopy is much higher than the corresponding for the HPLC methodology.
Abstract: We applied a noninvasive method to assess bone structural integrity. The method is based on the measurement of the dynamic characteristics of the bone (quality factor and modal damping factor) by applying vibration excitation in the range of acoustic frequencies, in the form of an acoustic sweep signal. Excised sheep femora were tested to detect changes in modal damping, density (kg/m3), bone mineral density (kg/m2) and bone mineral (hydroxyapatite) percentage. The changes were recorded after each time of chemical treatment of the bones performed to gradually cause mineral removal, thus simulating osteoporosis. It was shown that the change in quality factor and damping was in all cases on average equal or greater to the change in all other measured characteristics, thus strengthening the potential of the proposed method to become a valuable assessment tool for monitoring bone integrity and osteoporosis.
Abstract: Methodologies based on FT-Raman spectroscopy and HPLC were developed for monitoring the stability of lovastatin in the solid state in the presence of gallic acid, a natural antioxidant. A Raman calibration curve was constructed using the area of the strong but overlapping vibration mode of lovastatin at 1645 cm(-1) and of the gallic acid at 1595 cm(-1). Mixtures of the active ingredient with the antioxidant were heated in the presence of atmospheric air up to 120 degrees C. The molar ratios of lovastatin and gallic acid in the artificially oxidized mixtures were determined from their Raman spectra using the calibration curve. The results were compared to those obtained from the application of the HPLC methodology and found to match satisfactorily. The HPLC analysis was based on a reserved-phase Zorbax C(g), 10 microm (4.6mm x 25 cm i.d.) column, using a gradient elution program by varying the proportion of solvent A acetonitrile 100% to solvent B 0.1% v/v phosphoric acid, and a programmable diode array detection at 225 nm. The Raman methodology was simpler and non-destructive for the sample but yielded only molar ratios as opposed to the HPLC technique where the moles of the both ingredients were determined.
Abstract: A novel method based on differential pulse polarography (DPP) was developed for the non-destructive monitoring of pyroxicam (PXC) release from biodegradable and sterically stabilized poly(lactide-co-glycolide) (PLGA)-monomethoxypoly-(ethyleneglycol) (mPEG) nanoparticles. The nanoparticles were prepared by a precipitation-sol vent diffusion method. Approximately 30 mg l(-1) PXC was entrapped in the nanoparticles leading to a 0.56% PXC loading value. The continuous in vitro monitoring yielded the respected release profile and it was found that virtually all the drug was released within 3 days. There was no interference of the PLGA-mPEG dispersion on the DPP signal of PXC. DPP results were compared with those obtained from the application of the currently used, more cumbersome and destructive, methodology involving hydrolysis of the polymeric nanoparticles and subsequent determination of the drug spectrophotometric ally. A less than 1.5% difference was observed leading to the conclusion that the proposed methodology may be considered to be suitable for the in situ non-destructive determination of the in vitro release profile of electroactive drugs from nanoparticles. (C) 2003 Elsevier B.V. All rights reserved.
Abstract: A methodology based on FT-Raman spectroscopy and standard addition was developed for the analysis of minerals and was applied successfully for the quantitative determination of calcite in Ekeberg marble. The areas of the overlapping v, vibration modes of the dolomitic (1098 cm(-1)) and calcitic (1086 cm(-1)) carbonate groups were used, after deconvolution, for constructing a calibration curve. Application of the calibration curve on Raman spectra obtained from an Ekeberg sample yielded the calcite content which was found to be 5.7% (w/w). (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: Fourier Transform Infrared Spectroscopy (FT-IR) was used successfully for the simultaneous quantitative analysis of calcium carbonate phases (calcite, aragonite, vaterite) in ternary mixtures. From the FT-IR spectra of pure calcite, aragonite and vaterite powders with KBr, the absorptivities, alpha, of the absorption bands at 713 cm(-1) for calcite, 745 cm(-1) for vaterite, 713 and 700 cm(-1) for aragonite, were determined. In order to overcome the absorption band overlapping a set of equations based on Beer's law was developed. The detection limits were also established and found to be 1.1 x 10(-4) mg calcite per mm(2) of pellet at 713 cm(-1), 3.6 x 10(-4) mg aragonite per mm(2) of pellet at 700 cm(-1), 1.8 x 10(-4) mg aragonite per mm(2) of pellet at 713 cm(-1) and 3.1 x 10(-4) mg vaterite per mm(2) of pellet at 745 cm(-1). Analysis of a known ternary mixture of calcium carbonate polymorphs tested the validity of the method.
Abstract: The solubility of Nd2O3 in NdF3-LiF-MgF2 melts is about 0.08-0.38 mol% when the NdF3 concentration varies from 15 to 30 mol% at 900degreesC. The solubility increases from 0.13 mol% at 750 degreesC to 0.22 mol% at 900 degreesC in the NdF3-LiF eutectic. When MgF2 is added to NdF3-LiF binary melts saturated with Nd2O3, the Nd2O3 solubility seems to decrease slightly at 30 mol% NdF3, while a slight increase was observed with 15 mol% NdF3 in the binary. When dissolving Nd2O3 in the NdF3-LiF eutectic Raman spectroscopy showed that the complex ions NdOFx(x-1)- and Nd2OF(x+3)((x-1)-) may form in the melt. The most reasonable candidates seem to be: NdOF43- and NdOF54- among the mononuclear compounds and Nd2OF106-, Nd2OF84- among the binuclear complexes.
Abstract: On the basis of blend polymer electrolytes of polybenzimidazole and sulfonated polysulfone, a polymer electrolyte membrane fuel cell was developed with an operational temperature up to 200degrees C. Due to the high operational temperature, the fuel cell can tolerate 1.0-3.0 vol % CO in the fuel, compared to less than 100 ppm CO for the Nafion-based technology at 80degrees C. The high CO tolerance makes it possible to use the reformed hydrogen directly from a simple methanol reformer without further CO removal. That both the fuel cell and the methanol reformer operate at temperatures around 200degrees C opens the possibility for an integrated system. The resulting system is expected to exhibit high power density and simple construction as well as efficient capital and operational cost. (C) 2002 The Electrochemical Society.
Abstract: PURPOSE: Arsonolipid-containing liposomes have been recently prepared. The demonstrated antileukemic action of arsenic trioxide prompted us to study their effect on the viability of several types of cancer cells to investigate the possibility of relevant applications. Five different cell types, three malignant (HL-60, C6. and GH3) and two non-malignant (HUVEC and RAME), were used. METHODS: Liposomes containing the palmitoyl side chain arsonolipid (with different lipid compositions) were incubated with a given number of cells. Cell viability was estimated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-dimethyltetrazolium bromide assay. Morphologic studies were also performed. RESULTS: Our results reveal that arsonoliposomes cause a dose (initiated at 10(-6) M)- and time-dependent inhibition of survival in all three malignant cell lines studied. No significant effect on the survival of the normal cells studied was observed at these, as well as at 10-fold higher. concentrations, although arsenic trioxide was toxic to HUVEC cells at equivalent arsenic concentrations. Microscopy studies reveal that although morphologic changes were initiated in HL-60 and C6 cells after incubation with arsonoliposomes, no changes in HUVEC and RAME cells were observed. CONCLUSIONS: Considering the numerous advantages of liposomal systems in therapeutics, it is concluded that the arsonoliposome system is very interesting and future applications should be exploited by further studies.
Abstract: A simple methodology based on the differential pulse polarography (DPP) was developed for non-destructive monitoring of drug release from liposomes. The methodology was also capable of determining not only the released material that remained free in the liposomal suspension but also the amount of the drug which was eventually adsorbed on the vesicles surface after its release from the liposomes. Based on this methodology the release kinetics of encapsulated chlorothiazide in 5 mg ml(-1) DRV liposomes was studied at 37 degrees C at pH 7.4. The results were compared to those obtained by centrifuging the DRV sample and measuring the free drug in the supernatant solution with UV-spectroscopy. Approximately 70% of the initially encapsulated drug were released within 24 h of which ca. 46% were subsequently adsorbed on vesicles' surface.
Abstract: The phosphoric acid doping levels of homogeneous membranes from blends of polybenzimidazole (PBI) with sulfonated polysulfones (SPSF) were established and found to be dependent on the PBI/SPSF ratio, on the presence of 'non-bonded' PBI, on the sulfonation degree of the SPSF as well as on the impregnation temperature. Optimum parameters for using these blends in polymer electrolyte fuel cells were set. Ionic conductivity of these acid doped membranes at 160 degreesC was Found considerably higher than the conductivity of acid doped PBI membranes. (C) 2001 Elsevier Science Ltd. All rights reserved.
Abstract: Polymeric membranes from blends of sulfonated polysulfones (SPSF) and polybenzimidazole (PBI) doped with phosphoric acid were developed as potential high-temperature polymer electrolytes for fuel cells and other electrochemical applications. The water uptake and acid doping of these polymeric membranes were investigated. Ionic conductivity of the membranes was measured in relation to temperature, acid doping level, sulfonation degree of SPSF, relative humidity, and blend composition. The conductivity of SPSF was of the order of 10(-3) S cm(-1). In the case of blends of PBI and SPSF it was found to be higher than 10(-2) S cm(-1). Much improvement in the mechanical strength is observed for the blend polymer membranes, especially at higher temperatures. Preliminary work has demonstrated the feasibility of these polymeric membranes for fuel-cell applications. (C) 2001 The Electrochemical Society.
Abstract: Differential pulse polarography (DPP) was used for non-destructive monitoring of chlorothiazide (CHT) released from dehydration-rehydration liposomal vesicles (DRV) prepared from egg phosphadicholine (PC), dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC) and negatively-charged liposomes with the addition of phosphatidic acid (PA) to PC, DSPC and DPPC lipids. The release was found to be dependent on lipid composition and increased, as percentage of the initially loaded drug, in the following order: DSPC < DPPC < DSPC:PA < PC < DPPC:PA < PC:PA. The developed methodology was also capable of determining the adsorbed drug on liposomes as opposed to the currently-available techniques. Adsorption was also found to be dependent on lipid composition, but the influence of the surface charge on adsorption percentage was less pronounced. (C) 2001 Elsevier Science B.V. All rights reserved.
Abstract: The electrochemical behaviour of the systems LiF-NdF3, LiF-Nd2O3 and LiF-NdF3-Nd2O3 was investigated by means of cyclic voltammetry. Neodymium fluorides were reduced, from LiF-NdF3-Nd2O3 melts, via a three-electron reaction to Nd-0 that were deposited on the electrode substrate. Neodymium oxyfluorides were oxidised at anode to oxygen, which was evolved before the oxidation of F-. (C) 2001 Elsevier Science Ltd. All rights reserved.
Abstract: A nondestructive analytical method based on the use of Fourier transform Raman spectroscopy (FT-RS) for identification and quantitative analysis of hydroxyapatite (HAP) and collagen (COL) In bones was developed. A calibration curve based on the Raman spectra of known powder mixtures of HAP-COL was constructed with the use of the Raman bands at 960 cm(-1) for HAP and 2937 cm(-1) for COL. It was found that I-960/I-2937 = 0,46/W-c - 0.36, where I-960 and I-2937 are the relative intensities for the 960 and 2937 cm(-1) Raman bands, respectively, and W-C represents the weight fraction of collagen. The detection limit for HAP and COL was found to be 2.8 and 0.6 wt %, respectively. The potential of using RS for an in vitro point-by-point analysis ("mapping") of bones was demonstrated successfully on an artificially demineralized ox femur sample.
Abstract: There is a need for the quantitative determination of the ternary mixtures of calcium carbonate polymorphs (calcite, aragonite and vaterite), which are present in a number of materials including limestones, industrial scale formation and several pathological cases. Application of infrared spectroscopy proved to be inadequate, due to band overlapping, while use of Raman spectroscopy and X-ray powder diffraction (XRD) has been reported only for the calcite-aragonite mixture. In order to address the problem, a comprehensive non-destructive methodology for the simultaneous quantitative determination of the calcium carbonate crystal phases in their ternary mixtures based on the use of Fourier transform Raman spectroscopy (FT-RS) was developed. Binary mixtures were used to construct the calibration graphs using the Raman bands at 711 cm(-1) for calcite, 700 cm(-1) for aragonite and 750 cm(-1) for vaterite. Detection limits were found to be 0.13, 0.18 and 1.3 mol.-% for calcite, aragonite and vaterite, respectively, while the relative errors in determining the mol.-% of a known ternary mixture of calcium carbonate polymorphs were 1.6% for calcite, 0.3% for aragonite and 1.1% for vaterite. A similar methodology was developed using XRD. XRD calibration graphs were constructed using the 104 reflection of calcite, the 221 reflection of aragonite and the 110 reflection of vaterite. Detection limits for calcite, aragonite and vaterite were found to be 0.90, 2.90 and 6.90 mol.-%, respectively, while the relative errors in determining the mol.-% of the same ternary mixture used for testing the FT-RS methodology were 2.5, 1.8 and 0.6%, for calcite, aragonite and vaterite, respectively.
Abstract: Fourier transform infrared spectroscopy (FT-IR) and Fourier transform Raman spectroscopy (FT-RS) were used in order to characterize the encrusted deposits formed on a metallic thermosensitive prostatic stent. A 4 mm urinary stone entrapped within the lumen was also analyzed, Six different substances, a very rare occurrence, were detected, yielding complex spectra. Struvite (STR), hydroxyapatite (HAP), calcium oxalate monohydrate (COM), potassium urate (PU), and ammonium urate (AU) were the main components of concretion formed on the metal surface. STR and PU were detected on the 0.2 mm external surface of the stone, while the 3.8 mm core was found to be uric acid (UA). The broad and overlapping FT-IR bands of STR and COM made their identification difficult, while the detection of HAP was hindered by the presence of numerous urates bands, which, on the other hand, were used for the discrimination among UA, AU, and PU, Raman spectroscopy proved to be more sensitive tct urate presence than did FT-IR, while the identification of STR, COM, and HAP was easier for FT-RS but more difficult with respect to AU and UA since all their bands, but three, coincide. A combination of the two techniques was necessary for the qualitative analysis of the encrustation and the stone.
Abstract: A methodology based on differential pulse polarography (DPP) was developed for the quantitative, non-destructive determination of the entrapped, adsorbed and free chlorothiazide (CHT) in the presence of liposomes. Results were compared to those obtained from the application of conventional procedure and found equally reliable. Discrimination between adsorbed and free CHT and the capability for non-destructive determination of the entrapped drug were among the advantages of DPP methodology over the currently used technique. From the application of DPP to a 1 mg ml(-1), 4.5 mu m diameter liposome solution, it was found that drug adsorption was dependent on whether or not drug was entrapped in liposomes, it being twice as large for the empty liposomes. The amount of encapsulated CHT was found to be linearly dependent on the drug concentration, up to 100 mg l(-1), present during the encapsulation procedure and stabilized to a maximum when larger CHT concentrations were used. (C) 2000 Elsevier Science B.V. All rights reserved.
Abstract: The need for evaluating the retention of drugs in liposomes has lead to development of a new methodology, based on the differential pulse polarography (DPP), for the simultaneous quantitative determination of non-entrapped diazepam (DZP) and PC liposomes in a buffered solution, pH 7.4, at 37 degrees C, It was found that DZP polarographic signal depends both on liposome concentration and liposome size. Calibration plots of the DZP concentration vs, the current intensity in the presence of different lipid concentration were constructed. The liposome and DZP concentration were determined using these plots and the "standard addition" technique, The DPP detection limit for DZP was found to be 15 mu g l(-1) while for liposomes in samples with 6 mg l(-1) DZP was calculated to be 0.01 mg ml(-1). (C) 1999 Elsevier Science B.V, All rights reserved.
Abstract: Differential Pulse Polarography (DPP) was used for the quantitative determination of the free and adsorbed (non-entrapped) chlorothiazide (CHT) in the presence of liposomes. It was found that CHT polarographic signal depends both on the concentration of multilamelar (MLV) liposomes, due to its adsorption on the liposomal surface, and on their size. Calibration plots of CHT concentration versus current density, at pH 7.4, in the presence of different liposomes concentrations were constructed. Based on these curves the non-entrapped chlorothiazide was determined. Results were compared to those obtained from the application of conventional procedure i.e. chromatographic separation of CHT from liposomes followed by UV spectrophotometric determination. Both techniques were found to be comparable with respect to their accuracy, with a relative error of 0.47%. Determination of the drug using DPP was faster.
Abstract: The effect of operational variables in the process of melt crystallization of epsilon-caprolactam, including water content and cooling rate was investigated, It was found that the metastable range depends linearly on the water content. Higher cooling rates resulted in higher water content of the epsilon-caprolactam crystals grown in water containing melts. In the presence of water, higher cooling rates resulted in the formation of less elongated crystals, In suspensions, the epsilon-caprolactam crystals formed agglomerates. The agglomeration kinetics of crystallites grown from unstirred melts containing 10% w/w water found to fit the perikinetic model.
Abstract: Mineral components of a urinary stone forming layers have been analyzed with the use of Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FT-IR), and X-ray powder diffraction (XRD). The three spectroscopic methods were compared with respect to their capability of yielding reliable analytical qualitative results. The application of RS yielded less crowded spectra with sharper bands in comparison with those obtained by FT-IR. The analysis of the various mineral layers found in a human stone was possible with RS by focusing the laser beam at the desired layer. Overlapping broad bands were produced from the application of FT-IR, which made it difficult to identify components whose bands showed overlapping. Powder XRD could not be used for accurate analysis of the mineral components of the various stone layers since the material contained in the layers of small stones is not sufficient for analytical purposes. Moreover, the necessary stone grinding precludes the possibility of mineral topological analysis.
Abstract: The chemistry of tungsten chlorides in the LiCl/KCl eutectic has been investigated by Raman spectroscopy between 400 and 500 degrees C. It has been found that W(VI) is reduced to W(V) directly by the free Cl- ion in the melt and the octahedral complex ion WCL6- is formed. Addition of metals (Al, Zn, Pb, W) causes further reduction of W(V). Depending on the metal added WCl62- or W metal can be obtained.
Abstract: The nucleation of E-caprolactam in melts containing water impurities between 3% and 7% w/w was investigatedin a batch reactor monitoring melt temperature. The induction times preceding the formation of epsilon-caprolactam nuclei were inversely proportional to the melt supersaturation and a threshold in the supersaturation of about 6% was found for homogenous nucleation. The interfacial tensions calculated using the classical nucleation theory ranged between 0.8 and 1.5 mJ m(-2) for water content of 3%-7%, respectively. The concomitant increase of the size of the critical nucleus suggested that water inhibits the process of nucleation of epsilon-caprolactam in melts containing water impurity, This conclusion was further confirmed for the rates of crystal growth of the epsilon-caprolactam in the melts measured from the rates of temperature increase with time.
Abstract: A non-destructive method based on the use of Raman spectroscopy (RS) for the determination of the percentage of gypsum in sulfated marble is presented, The Raman spectra of well mixed powder samples of calcite-aragonite, calcite-gypsum and gypsum-aragonite pairs of mixtures were recorded and the characteristic bands at 280 cm(-1) for calcite, 205 cm(-1) for aragonite and 412 cm(-1) for gypsum were used as the basis for the quantitative analysis of specimens in which the most stable calcium carbonate phases, calcite and aragonite, were present, The detection limits mere found to be 0.3 mol% for calcite, 0.5 mol% for aragonite and 0.6 mol% for gypsum, For samples containing only one calcium carbonate phase the use of the strong and sharp Raman band at 1085 cm(-1), common for aragonite and calcite, together with the intensity of the Raman peak at 1006 cm(-1) for gypsum, yielded lower detection limits: calcite 0.1, aragonite 0.1 and gypsum 0.05 mol%, The analysis by RS was compared with X-ray powder diffraction (XRD), In this analysis, the calibration curves mere constructed using the relative intensities corresponding to the 113, the 111 and the 12 (1) over bar reflections of the calcite, aragonite and gypsum, respectively, The detection limits for calcite, aragonite and gypsum mere 4, 5 and 1-2 mol%, respectively, The potential of using RS for a point-by-point analysis ('mapping') of a surface by focusing the laser beam on the selected spots was also demonstrated on a marble sample removed from Athens National Garden, exposed in the open air.
Abstract: A quantitative analytical methodology based on Raman spectroscopy (RS) was developed for the compositional analysis of binary solid mixtures consisting of calcium oxalate monohydrate (COM) and hydroxyapatite (HAP). The ratios of the relative intensities of the Raman bands corresponding to HAP and COM were used for the construction of calibration curves used for the quantitative analysis. The intensities at 960 cm(-1), I-RHAP and 1462 cm(-1), I-RCOM, for HAP and COM, respectively, in the Raman spectra of each salt were used. A linear dependance was found for the ratio I-RHAP/I-RCOM on the inverse of the COM concentration (mole fraction) in the solid, binary mixtures. Comparison of this method with quantitative analysis of binary HAP-COM by powder X-ray diffraction (XRD), using the relative intensities of the 002 reflection of HAP and the 020 reflection of COM showed that although the limit of detection was comparable (approx. 1 mol%), RS analysis offered the relative advantage of performing analyses without the need of grinding the samples, thus making it possible for the analysis of layered deposits of the minerals investigated. (C) 1997 Elsevier Science B.V.
Abstract: The potential use of the Raman spectroscopy (RS) for the quantitative analysis of the mineral components of urinary stones consisting mainly of the mono- and dihydrate salts of calcium oxalate has been demonstrated. The quantitative analysis was based on the construction of calibration curves made of known mixtures of synthetically prepared pure calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD), The Raman spectra of well-mixed powdered samples of COM and COD were recorded, and the characteristic bands at 1462 and 1477 cm(-1) for COM and COD, respectively, were used as the basis for the quantitative analysis. It was found that x(M) = (I-R - 0.134)/(0.8I(R) + 1.52), where x(M) is the molar fraction of COM in the solid mixture anti I-R represents the intensity ratio of the Raman band at 1462 cm(-1) to that of 1477 cm(-1). The calibration curve was used for the analysis of a typical urinary stone surgically removed, and it was found that x(M) = 0.33. This finding was confirmed by infrared quantitative spectroscopic analysis. Quantitative analysis using the proposed Raman technique had a detection limit of approximately 0.6 mol % content in COM. The relative advantage of RS lies in its potential use as a nondestructive analytical technique for the mineral composition of urinary stones.
Abstract: Laser Raman spectroscopy was used for the quantitative analysis of the most common impurities contained in epsilon-caprolactam: adipic acid, sodium sulfate and ammonium sulfate. Calibration graphs were constructed from spectra obtained from pellets with known quantities of epsilon-caprolactam and each of the impurities. Linear relationships between the caprolactam content and the ratio of the relative intensities at characteristic wavelengths were found for the impurities examined. The calibration lines were defined as: adipic acid-epsilon-caprolactam I-915/I-746 = chi(cap)(-1) 0.62 - 0.58; ammonium sulfate-epsilon-caprolactam I-975/I-746 = chi(cap)(-1) 2.78 - 2.23; and sodium sulfate-epsilon-caprolactam I-994/I-746 = chi(cap)(-1) 4.26 - 4.45. I is the relative Raman intensity at the wavenumber noted by the subscript and chi(cap) is the molar fraction of caprolactam. The detection limits are better than 1 mol% for the impurities examined.
Abstract: Partially stabilized zirconias were prepared by using CaO, MgO, and Y2O3, as dopants. The sintered ceramics were immersed in molten LiF, NaF, KF eutectic for up to 360 h. The tetragonal-to-monoclinic transformation, which was induced in the crystal structure from the abrasive environment, was probed with laser Raman spectroscopy and scanning electron microscopy. A change in the crystal structure was found by using microprobe analysis, which was caused by dopant's depletion. Ceramics' resistance to molten fluorides was studied by observing the phase transformation and found to be dependent on immersion time, pore size, stabilizer percentage, and firing conditions.
Abstract: A one-end-open graphite cylinder which was coated externally with pyrolytic boron nitride, except the bottom, was used successfully as the container of a reference electrode for use in fluoride melts. The electrode consists of a nickel wire or silver wire immersed in a solution of nickel or silver fluoride in LiF-NaF-KF (FLINAK) eutectic. It was tested by using both the Ni-Ni(II) and the Ag-Ag(I) redox couples at temperatures between 650 and 800 degrees C. The emf between two identical electrodes was stabilized within 3 h after the immersion in the bath and a Nernstian response with temperature was observed. The electrode was found to be stable for more than 50 h and could be reused with reproducible results. No potential shift was observed in cyclic voltammograms which were obtained, with a lapse of 12 h, from FLINAK with 0.1 mol% K2NbF7.
Abstract: Yttria-fully stabilized zirconia ceramics were manufactured from home-made and commercially available powders and were sintered under different conditions. The ceramics were immersed in the corrosive environment of molten LiF, NaF, KF (FLINAK) eutectic for up to 360 h from 700-900 degrees C. The changes caused in the crystal structure were probed with laser Raman spectroscopy and X-ray diffraction. The degree of corrosion (phase transformation) depends on immersion period, FLINAK temperature, and ceramics microstructure. From the tested ceramics, ZrO2-8 mol% Y2O3 with a grain size larger than 8 mu m and having zero open porosity, exhibits the best resistance to the. corrosive influence of FLINAK.
Abstract: Laser Raman spectroscopy was used for the quantitative determination of aspirin in aspirin-maize starch tablets. A calibration curve was constructed from spectra obtained from tablets with known quantities of aspirin and starch. The calibration curve is given from the relationship: I(552)/I(478) = (W(aspirin)/W(starch)) x 4.21, where I(552) and I(478) are the relative Raman intensities for the 552 and 478 cm(-1) Raman shift, respectively. W(aspirin) and W(starch) represent the weight of aspirin and starch in a pellet.
Abstract: Vibrational Raman spectroscopy was employed successfully for the simultaneous quantitative determination of the cubic, tetragonal and monoclinic phases of partially stabilized zirconia. Pressed pellets with known composition were prepared and used as standard mixtures. From the standard pellets, a calibration curve was obtained which was found to be a straight line if (/(640) - 0.47 /(260))//(177) is plotted against the inverse monoclinic molar fraction. /(260), /(177) are the Raman intensities for the tetragonal and monoclinic peaks at 260 and 177 cm(-1) respectively, and were calculated by subtracting the ''background''. In contrast, /(640) represents the intensity for the 640 cm(-1) band, which is attributed to all three phases, and was measured including the ''background''.
Abstract: Vibrational Raman spectroscopy was used successfully for the quantitative determination of the cubic and monoclinic phases of zirconia. Pressed pellets with known composition were prepared using monoclinic and cubic powders from different manufacturers and were used as standard mixtures. An intensity ratio plot of the 617-cm-1 band, which is attributed to the presence of both phases, to either the 177-cm-1 or 476-cm-1 monoclinic band against the inverse monoclinic molar fraction (chi) yielded a straight line which was described by ratio = 0.11 chi-1 + 0.26 and ratio = 0.12 chi-1 + 0.29, respectively. The method was found to be independent of the origin of the powders.
Abstract: Fractures are the most frequent health problem associated with bone. Metabolic diseases, such as osteoporosis, affect skeletal integrity, reduce strength and toughness of bone and lead to increased risk of fragility. In the present work, changes in the amount and/or quality of bone were studied in osteoporotic tibiae from female wistar rats compared to healthy controls. Osteoporosis was induced through ovariectomy. Bone composition and quality was evaluated employing Raman Spectroscopy. Several spectra were recorded. The height of the primary phosphate band (PO43-, v1) for the mineral at 959 cm-1, the carbonate peak at 1070 cm-1 under the combined phosphate-carbonate envelope 1010-1100 cm-1 spectral range, the matrix bands at 855 cm-1 (hydroxyproline), 875 cm-1 and 920 cm-1 (proline), as well as the three major peaks under amide I envelope (1620-1710 cm-1) were measured after proper baselinining and deconvolution. The mineral to matrix ratio [959 cm-1 / (855 cm-1 + 875 cm-1 + 920 cm-1)] was reduced, suggesting decreased mineral quantity in the osteoporotic tibiae compared to controls. Carbonate levels remained stable which implies absence of new bone tissue formation, though bone is known to follow a constant renewal procedure. The mineral to amide I envelope ratio exhibited an increasing trend suggesting that amide I cannot be used as collagen metrics as it is subject to polarization effects. Further analysis of the amide I envelope shows that the band changes shape following bone disease, which is a result of the change in the ratio of the peaks lying under the amide I envelope. Therefore, changes in collagen cross-linking accompany reduction of mineral amount and lead to reduced strength and increased fragility in osteoporosis.
Abstract: The contemporary methods for the assessment of the quality of human mandible, in order to facilitate the decision making for dental implants, include bone density measurements through dual-energy X-Ray absorptiometry (DEXA) or its variations. The estimation of mandible quality with these methods is related to subjectivity, comparability and reliability problems, which result in restricted capability of secure assessment of bone quality. Monitoring of loss of structural integrity is applied in this work through modal analysis and Raman Spectroscopy, in order to obtain objective assessment of mandible bone quality. Specifically, modal damping factor (MDF), bone mineral density (BMD) and Raman measurements are performed on human cadaveric mandibles. From the data acquired clearly arises a very promising correlation between MDF, BMD and RAMAN, reinforcing the belief from our previous research findings that the MDF method can lead to a mandible quality assessment tool, thus encouraging further research investigation.)
