Liquid-Liquid Extraction, Separation, Preconcentration, and ICP-AES Determination of Lanthanum and Cerium with N-Phenyl-(1,2-methanofullerene C60)61-formohydroxamic Acid

A novel method for liquid-liquid extraction, separation, preconcentration, and simultaneous trace determination of cerium(IV) and lanthanum(III) with N-phenyl-(1,2-methanofullerene C₆₀)61-formohydroxamic acid (PMFFA) is reported. Lanthanum and cerium are extracted at pH 8.5 and 9.5, respectively in chloroform and recovered from monazite sands in the presence of thorium, uranium, and large number of cations and anions in high purity (99.98%). The extraction mechanism is investigated. The influence of PMFFA, pH, diverse ions, and temperature on the distribution constants of lanthanum and cerium was examined. The overall stability constants (log β₂K_e) and extraction constants (K_ex) for lanthanum(III) are 22.50 and 5.0 × 10^-9, respectively and for cerium(IV) are 21.51 and 3.9 × 10^-9, respectively. Lanthanum(III) gives a colourless complex with PMFFA which is extracted into chloroform having molar absorptivity 5.5 × 10⁴ L mol^-1 cm^-1 at 395 nm, and Beer's law 0.12-2.52 µg mL^-1, while cerium(IV) forms a red coloured complex, λ_max 460 nm, molar absorptivity 1.5 × 10⁴ L mol^-1 cm^-1, and Beer's law 0.46-9.26 µg mL^-1. For trace determination the extracts were directly inserted into the plasma for inductively coupled plasma atomic emission spectrometry ICP-AES measurements of lanthanum and cerium which increases the sensitivity 60 folds and obey Beer's law in the range, 2.1-37.5 ng mL^-1 for lanthanum and 9.2-186.4 ng mL^-1 for cerium. The method is applied for the determination of lanthanum and cerium in real and standard samples, sea water, and environmental samples.     

A Novel Fullerene Hydroxamic Acid for the Liquid-Liquid Extraction, Separation, Preconcentration, and Spectrophotometric and ICP-AES Determination of Vanadium

A new reagent N-phenyl-(1,2 methanofullerene C₆₀)61-formohydroxamic acid (PMFFA) is reported for extraction and trace determination of vanadium(V) in nutritional and biological substrates. The extraction mechanism of vanadium from 6 M HCl media is investigated. The influence of PMFFA, diverse ions, and temperature on the distribution constant of vanadium examined. The over all stability constant (log β₂K_e) and extraction constant (K_ex) are 20.89 ± 0.02 and 8.0 ± 0.02 × 10^-15, respectively in chloroform. The thermodynamics parameters are calculated and kinetics of vanadium transport is discussed. The system obeys Beer's law in the range of 3.2-64.0 ng mL^-1 of vanadium(V). The molar absorptivity is 7.96 × 10⁵ L mol^-1 cm^-1, at 510 nm. The PMFFA-vanadium(V) complex chloroform extract in chloroform was directly inserted into plasma for ICP-AES measurement, which increases the sensitivity by 50 folds and obey Beer's law in the range of 50-1200 pg mL^-1 of vanadium(V). The method is applied for determination vanadium in real standard samples, sea water, and environmental samples.     

Development of matrix patches for transdermal delivery of a highly lipophilic antiestrogen

The aim of this study was to develop matrix-type transdermal systems (TDSs) containing the highly lipophilic (log P = 5.82) antiestrogen (AE) and the permeation enhancers propylene glycol and lauric acid. For that purpose, permeation of AE from various adhesive matrices through excised skin of hairless mice was evaluated. It was found that pretreatment of the skin with permeation enhancers raised the transdermal flux of subsequently applied antiestrogen. Highest steady-state transdermal fluxes (1.1 µg cm^-2 h^-1) were obtained from Gelva®, polyacrylate adhesive, followed by 0.55 µg cm^-2 h^-1 from Oppanol® polyisobutylene, 0.31 µg cm^-2 h^-1 from BIO-PSA® silicone, and 0.12 µg cm^-2 h^-1 from Sekisui polyacrylate matrices. In order to develop TDS with high content of fluid permeation enhancer propylene glycol, two different strategies were investigated. One strategy was the addition of hydroxypropyl cellulose (HPC) as thickening agent to Gelva matrices. This allowed for propylene glycol loading levels of up to 30%, resulting in transdermal AE fluxes of 0.09 µg cm^-2 h^-1. On the other hand, a fleece-laminated backing foil was loaded with the described permeation enhancer formulation and laminated with polyacrylate adhesive layer, resulting in transdermal AE fluxes of 0.06 µg cm^-2 h^-1. However, application of these TDSs on skin pretreated with permeation enhancers raised the fluxes to 2.6 µg cm^-2 h^-1 from Gelva/HPC and 0.46 µg cm^-2 h^-1 from fleece/Sekisui.     

Reaction Kinetics of C60 Fullerene Ozonation

It has been verified that the reaction between O₃ and C₆₀ follows the general second order reaction rate which is valid for all the reactions between ozone and unsaturated olefinic bonds: v = k[C=C][O₃]. The reaction rate constant k has been measured ≈(1.5 ± 0.3) × 10⁴ L mol^-1 s^-1. The value of this rate constant has the same order of magnitude of the rate constant measured for instance in the ozonation of 1,4-diphenylbutadiene.     

Stability-indicating spectrophotometric and densitometric methods for determination of aceclofenac

Three methods were developed for the determination of aceclofenac in the presence of its degradation product, diclofenac. In the first method, third-derivative spectrophotometry (D₃) is used. The D₃ absorbance is measured at 283 nm where its hydrolytic degradation product diclofenac does not interfere. The suggested method shows a linear relationship in the range of 4-24 µg mL^-1 with mean percentage accuracy of 100.05±0.88. This method determines the intact drug in the presence of up to 70% degradation product with mean percentage recovery of 100.42±0.94. The second method depends on ratio-spectra first-derivative (RSD₁) spectrophotometry at 252 nm for aceclofenac and at 248 nm for determination of degradation product over concentration ranges of 4-32 µg mL^-1 for both aceclofenac and diclofenac with mean percentage accuracy of 99.81±0.84 and 100.19±0.72 for pure drugs and 100.17±0.94 and 99.73±0.74 for laboratory-prepared mixtures, respectively. The third method depends on the quantitative evaluation of thin-layer chromatography of aceclofenac using chloroform:methanol: ammonia (48:11.5:0.5 v/v/v) as a mobile phase. Chromatograms were scanned at 274 and 283 nm for aceclofenac and diclofenac, respectively. The method determined aceclofenac and diclofenac in concentration ranges of 2-10 and 1-9 µg spot^-1 with mean percentage accuracy of 100.20±1.03 and 100.14±0.98 for pure drugs and 99.77±0.74 and 100.07±0.78 for laboratory-prepared mixtures, respectively. This method retains its accuracy in the presence of up to 80% degradation product for the studied drug.

The suggested procedures were checked using laboratory-prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparation. The validity of the proposed methods was further assessed by applying a standard addition technique. The obtained results agreed statistically with those obtained by the reported method.     

Degradation of tobramycin in aqueous solution

The kinetics of degradation of tobramycin (Ne-De-Ka) in aqueous solution was studied as a function of pH. Tobramycin hydrolyzes in acidic solution to yield kanosamine (Ka-OH) and nebramine (Ne-De-OH) with a pseudo first-order rate constant of 2.7 × 10^-6 s^-1 in 1 N HCl at 80°C. The activation energy for the acid catalyzed hydrolysis is 32 kcal mol^-1. In basic solution, the hydrolysis products are deoxystreptamine (De-OH), nebramine (Ne-De-OH) and deoxystreptamine-kanosaminide (HO-De-Ka). The pseudo first-order rate constant for the hydrolysis in 1 N KOH is 1 × 10^-8 s^-1 at 80°C. The activation energy for the base catalyzed hydrolysis is 15 kcal mol^-1. Tobramycin is very stable towards hydrolysis at neutral pH; however, it rapidly oxidizes giving several products including De-OH, Ne-De-OH, and HO-De-Ka. In pH 7 phosphate buffer (0.01 M), the t₉₀ value is 70 hr at 80°C.     

Surface Preparation of Aluminum Nitride for Metallization: Effect of Temperature on Surface Reactivity

The current aqueous cleaning step in the surface preparation of aluminum nitride (AlN) prior to metallization causes performance and reliability issues for the substrates used for microelectronic packaging due to surface reactions. These issues limit the use of AlN and its replacing of BeO, an environmentally hazardous material currently used. The aim of this investigation was to determine the effects of different solutions on the surface of AlN substrates under varying conditions at times up to 2419.2 ks (28 days). Concentration of the solutions, temperature, and immersion time were varied for the AlN samples in the solutions. Both elevated temperatures (50°C and 90°C) and low temperatures (5°C) were investigated.

Four general types of behavior were observed: minor changes in average surface roughness and microstructure, linear change in average surface roughness and pitted grains, nonlinear change in average surface roughness and product formation on AlN surface, and miscellaneous change in average surface roughness with surface product formation.

The surface roughening kinetics were very complex due to changes in both the reaction product morphology and reaction mechanism with temperature, solvent, and pH for a specific solvent. Minor changes in average surface roughness and microstructure were observed for HCl pH = 5, H₂ SO₄ pH = 5, NaOH pH = 8, NaOH pH = 10, NaOH pH = 12, deionized water and Alfred tap water at 5°C, HCl pH = 3 and oleic acid at 50°C and citric acid and oleic acid at 90°C. Linear changes in average surface roughness and pitted grains were observed for HCl pH = 2 and H₂SO₄ pH = 3 at 50°C and HCl pH = 2, H₂SO₄ pH = 3, and deionized water at 90°C. Non-linear change in average surface roughness and product formation on AlN surface was observed for HCl pH = 5, NaOH pH = 8 and Alfred tap water at 50°C and HCl pH = 5 and H₂SO₄ pH = 2 at 90°C. Miscellaneous changes in average surface roughness with surface product formation were observed for H₂SO₄ pH = 2, H₂SO₄ pH = 5, NaOH pH = 10, NaOH pH = 12, citric acid, Micro-90 and deionized water at 50°C and HCl pH = 3, H₂SO₄ pH = 5, NaOH pH = 8, NaOH pH = 10, NaOH pH = 12, Micro-90 and Alfred tap water at 90°C.     

Dissolution and solubility behavior of fenofibrate in sodium lauryl sulfate solutions

The solubility of fenofibrate in pH 6.8 McIlvaine buffers containing varying concentrations of sodium lauryl sulfate was determined. The dissolution behavior of fenofibrate was also examined in the same solutions with rotating disk experiments. It was observed that the enhancement in intrinsic dissolution rate was approximately 500-fold and the enhancement in solubility was approximately 2000-fold in a pH 6.8 buffer containing 2% (w/v) sodium lauryl sulfate compared to that in buffer alone. The micellar solubilization equilibrium coefficient (k*) was estimated from the solubility data and found to be 30884 ± 213 L/mol. The diffusivity for the free solute, 7.15 × 10^- 6 cm²/s, was calculated using Schroeder's additive molal volume estimates and Hayduk-Laurie correlation. The diffusivity of the drug-loaded micelle, estimated from the experimental solubility and dissolution data and the calculated value for free solute diffusivity, was 0.86 × 10^- 6 cm²/s. Thus, the much lower enhancement in dissolution of fenofibrate compared to its enhancement in solubility in surfactant solutions appears to be consistent with the contribution to the total transport due to enhanced micellar solubilization as well as a large decrease ( ∼ 8-fold) in the diffusivity of the drug-loaded micelle.     

Effect of Erodent Particle Hardness on Velocity Exponent in Erosion of Steels and Cast Irons

This article reports the effect of hardness of erodent particles on velocity exponent of some weld deposited alloys. Three steels and two alloy cast irons were selected for the present investigation. The bulk hardness of the alloys was in the range of 300 to 800 HV, whereas erodnet particles were having hardness in the range of 400 to 1875 HV. Erosion tests were conducted with 125-150 µm cement clinker, 125-150 µm blast furnace sinter, 100-150 µm silica sand, and 125-150 µm alumina particles and at impingement angles of 30° and 90° and with impingement velocities in the range of 25 to 120 m sec^-1. The erosion rate showed power-law dependence on impingement velocity, E = kVⁿ, where kis a constant and nis the velocity exponent. The velocity exponents obtained in the present work were in the range of 1.91 to 2.52. The velocity exponent showed an increasing trend with increasing hardness of the alloys irrespective of the hardness of the erodent particles and the impingement angle. The velocity exponent increased with increasing hardness of erodent particles, irrespective of the impingement angle and hardness of the alloys. The velocity exponents obtained in the present work were rationalized with respect to erodent particle properties, material properties and erosion mechanisms.     

Determinatiom of the Rydrolysis of Quinolinium-I-Methyliocide-6-Carboxt-Methyl Ester by Glc

A CLC method for the determination of the hydrolysis of quiolinlues I-methyliodide-6-carboxy-mathylester is dascribed. GLC is parforsud on porous polymer composed of ethylvinylbenzena crose-linked with divinyl-bensen (Polapak-Q). The retention times of methyl alcohol and the internal standare (tertiary butanol) are 2.8 and 6.3 min., respectively. The- apparent pseudo-first order rate constants as a function of taparature (37.C and 50°C) in the presence of 6N HCl were calculated and found to be 2.6 × 10^-2 min^-1 and 2.7 × 10^-2 win-1 respactively.     

Photodegradation study of sodium usnate solution: influence of pH

Photodegradation of 2.6 × 10^-5 M aqueous solutions of sodium usnate at various pH was studied. Photodegradation appeared to follow first-order kinetics and was found to be pH dependent. The degradation rate constant was calculated to be 9.20 × 10^-4 min^-1, 5.93 × 10^-4 min^-1, 9.69 × 10^-4 min^-1, and 9.88 × 10^-4 min^-1 at pH 6, pH 7, pH 8, and pH 9, respectively.     

Stability of Mixtoxantrone Hydrochloride in Solution

A stability-indicating reversed-phase high performance liquid chromatographic method was developed for the detection of mitoxantrone HC1 and its degradation products under accelerated degradation conditions. The degradation kinetics of mitoxantrone HC1 in aqueous solution over a pH range of 1.18 to 7.20 and its stability in propylene glycol-or polyethylene glycol 400-based solutions were investigated. The observed rate constants were shown to follow apparent first-order kinetics in all cases. The pH-rate profile shows that maximum stability of mitoxantrone HC1 was obtained at pH 4.01. No general acid or base catalysis from acetate or phosphate buffer species was observed. The catalysis rate constants on the protonated mitoxantrone imposed by hydrogen ion water and hydroxy ion were determined to be 3.72 × 10 min^-1 5.64 × 10-min^-1 and 1.108 × 10^-2min^-1, respectively. The degradation rate constants of mitoxantrone affected by different ionic strength systems. Irradiation with 254 nm UV light at 25±0.5°C was found when canpared with the light-protected controls. Incorporation of nonaqueous propylene glycol or polyethylene glycol in the pH 4.01 mitoxantrone solution shows an increase in its stability at 502±0.5°C.     

Thermal optical properties of TiO2 films

A fibre optic experimental arrangement was used to determine the thermo-optic coefficient (dn/dT) of electron beam deposited titanium dioxide coatings on the cleaved end faces of multimode optical fibres for a wavelength range between 600 and 1050 nm. The temperature-induced change in the index of refraction (n) and extinction coefficient (k) were successfully determined from reflection spectra. Measurements of n and k at various wavelengths for different temperatures enabled the determination of dn/dT and dk/dT. It was found that dn/dT takes different values at different temperature ranges. For example, at 800 nm, dn/dT was (−1.77±0.7)×10⁻⁴ K⁻¹, between 18°C and 120°C, and took a value of (−3.04±0.7)×10⁻⁴ K⁻¹ between 220°C and 325°C.     

Ozone Reaction with C70 and C60 Fullerenes: The Effect of Temperature on the Reaction Kinetics

It has been confirmed that the effect of temperature on the rate constants (k) of ozone reaction with C₇₀ and C₆₀ fullerenes follows the Arrhenius law. The experimental values of activation energy (E_a) and pre-exponential factor (A), like as those of other simple alkenes, are in the order of 2.4-2.6 kcal mol^-1 and (1.2-1.8) × 10⁷ L mol^-1 sec^-1, respectively. They are practically equal for the both fullerenes. It has also been found that the value of the rate constant k of C₇₀ fullerene ozonolysis is higher in comparison to the respective k-value of C₆₀.     

Preparation, Electrical, and Dielectric Characterization of Crosslinked Polyvinyl Alcohol-Phosphotungstic Acid Nanocomposites

The work presents the electrical and dielectric characterization of proton-conducting, chemically-crosslinked nanocomposites of polyvinyl alcohol (PVA) and phosphotungstic acid (PTA). The composite membranes were prepared by in situ crosslinking of the polymer matrix in solution form, containing PTA. The electrical and dielectric properties of the membranes were investigated as a function of blending composition, crosslinking density, and temperature. The conductivity of these membranes shows a temperature dependence of Arrhenius type and highest conductivity of 3.31 × 10^-3 S cm^-1 was obtained. The activation energies for proton conduction were found to be in the range of 15.28-40.62 kJ mol^-1.     

AC Conductivity and Dielectric Response of Polycrystalline and Amorphous C70

The AC conductivity and dielectric constant of polycrystalline and amorphous C₇₀ samples were measured in the 75-300 K temperature range and in the 100 Hz to 1 MHz frequency range. For polycrystalline samples, we observe effects caused by O₂ intercalation due to prolonged exposure to ambient air. The conductivity σ of these samples around 300 K depends on the measuring frequency ν as a σ ∼ νⁿ with n ≈ 0.88, implying a strong reduction of DC conductivity to less than 10^-12 S/cm. The dielectric constant of polycrystalline samples shows an anomaly at 285 K which is interpreted as due to the transition from its intermediate rhombohedral phase into its monoclinic low-temperature phase. In contrast with the polycrystalline samples, the amorphous C₇₀ samples prepared by sublimation do not contain interstitial 0₂, their conductivity at 300 K is of about 10^-6 S/cm, is independent of frequency, and is well described by the hopping mechanism (Davis-Mott T^1/4 law) in the 200-300 K range. All evidence of phase transitions disappears in the amorphous samples.     

Increasing the aqueous solubility of acetaminophen in the presence of polyvinylpyrrolidone and investigation of the mechanisms involved

It was shown that the aqueous solubility of acetaminophen in the presence of polyvinylpyrrolidone (PVP) increased. The solubility at 25°C increased from 14.3 mg mL^-1 in the absence of PVP, to 19.7 mg mL^-1 in the presence of 4% w/v PVP, and to 26.7 mg mL^-1 in the presence of 8% w/v PVP. Dialysis studies indicated that there is a potential of binding between PVP and acetaminophen in their aqueous solutions. Dialysis studies also revealed that the nature of interaction between PVP and acetaminophen is physical and reversible, and there was no strong binding between PVP and acetaminophen in their solutions. Infrared spectroscopy of acetaminophen/PVP solid dispersion indicated that the mechanism of interaction between PVP and acetaminophen is via hydrogen bonding. Therefore, the increase in solubility of acetaminophen in the presence of PVP is probably attributed to its ability to form a water-soluble complex with PVP.     

Reactions in Au/Nb bilayer thin films

The interdiffusion and intermetallic compound formation of Au/Nb bilayer thin films annealed at 200–400 °C have been investigated. The bilayer thin films were prepared by electron beam deposition. The Nb film was 50 nm thick and the Au film was 50–200 nm thick. The interdiffusion of annealed specimens was examined by measuring the electrical resistance and depth-composition profile and by transmission electron microscopy. Interdiffusion between the thin films was detected at temperatures above 325 °C in a vacuum of 10^-4 Pa. The intermetallic compound Au₂Nb₃ and other unknown phases form during annealing at over 400 °C. The apparent diffusion constants, determined from the penetration depth for annealing at 350 °C, are 3.5 × 10⁻¹⁵ m² s⁻¹ for Nb in Au and 8.6 × 110^7minus;15 m² s⁻¹ for Au in Nb. The Au surface of the bilayer films becomes uneven after annealing at over 400 °C due to the reaction.     

CONTRIBUTIONS OF ROAD DUST RESUSPENSION TO THE AIRBORNE PARTICLE CONCENTRATIONS IN TAIPEI

The high concentrations of airborne particles have been one of the main air pollution problems in Taipei, Taiwan. In this study, the possible sources of airborne particles were investigated using concentration profile and chemical composition. The vertical concentration profile of TSP was measured at 1.5 m, 11 m, and 38 m above ground. The concentrations of TSP at 1.5 m above ground are always greater than 300 µg/m³; and even up to 1230 µg/m³, while those at 11 m above ground are only half of these values. The concentrations at 38 m above ground are only about half of those at 11 m above ground. Similar concentration profiles are found for Mg, Ca, Pb, Fe, and Zn measured and the enrichment factors with respect to the composition of road dust are generally less than 3. Therefore, there is a not upward flux of airborne particles from ground. The net upward fluxes are estimated to be about 100 ton/yr/km¹ from the vertical concentrations profiles and particle size distributions. The particle resuspension rates due to wind flow from a Teflon filter were also determined at the same time. The resuspension rates of particles by wind were found to be on the order of 10^-6 to 10^-5sec^-1. These particle resuspension fluxes are much smaller than those calculated by concentration profile. Other mechanisms, e.g. traffic-induced resuspension, are needed to be included in further study.