Separation and preconcentration of mercury in water samples by ionic liquid supported cloud point extraction and fluorimetric determination

We have developed a cloud point extraction procedure based on room temperature ionic liquid for the preconcentration and determination of mercury in water samples. Mercury ion was quantitatively extracted with tetraethyleneglycol-bis(3- methylimidazolium) diiodide in the form of its complex with 5,10,15,20-tetra-(4-phenoxyphenyl)porphyrin. The complex was back extracted from the room temperature ionic liquid phase into an aqueous media prior to its analysis by spectrofluorimetry. An overall preconcentration factor of 45 was accomplished upon preconcentration of a 20?mL sample. The limit of detection obtained under the optimal conditions is 0.08?μg mL^?1, and the relative standard deviation for 10 replicate assays (at 0.5?g mL^?1 of Hg) was 2.4%. The method was successfully applied to the determination of mercury in tap, river and mineral water samples.

Use of pyrocatechol violet modified sodium dodecyl sulfate coated on alumina for separation and preconcentration of uranium(VI)

A sensitive and selective solid phase extraction procedure for the determination of trace of uranium(VI) has been developed. An alumina-sodium dodecyl sulfate coated on with pyrocatechol violet was used for preconcentration and determination of uranyl ions by spectrophotometry method using Arsenazo III reagent. Sorbed ions were quantitatively eluted using 5 mL of 0.25 mol L⁻¹ HNO₃. The effects of parameters such as pH, amount of alumina, amount of ligand, flow rate, type and concentration of elution agent were examined. The capacity of the sorbent for U(VI) was found to be 0.92 mmol g⁻¹. The relative standard deviation was 1.28% for 10 replicate determinations of U(VI) ion in a solution with a concentration of 1.0 μg mL⁻¹. The practical applicability of the developed sorbent was examined using synthetic and real samples such as standard reference material 2709 (San Joaquin Soil) and 2711 (Montana Soil).     

Fabrication and characterization of anhydrous polymer electrolyte membranes based on sulfonated poly(vinyl alcohol) and benzimidazole

In the present study, a new type of chemically cross-linked polymer blend membranes consisting of poly(vinyl alcohol) (PVA), sulfosuccinic acid (SSA) and benzimidazole (BnIm), as a dopant, at different stoichometric ratios were prepared and used as proton conducting polymer electrolytes. The proton conductivities of the membranes were investigated as a function of blending composition and the temperature. TGA indicated that the blend polymers were thermally stable up to approximately 175°C; differential scanning calorimetry (DSC) results illustrated the homogeneity of the materials. The local chain flexibility of the host polymer increased with BnIm concentration. The methanol permeability values of the membranes were much lower than that of a Nafion-membrane. The proton conductivity of these materials increased with BnIm and SSA concentration and the temperature.     

Poles of L-Functions on Quaternion Groups

The author shows that the (partial) standard Langlands L-functions on quarternion groups have at most simple poles at certain positive integers.     

An EPR study of Cu doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) single crystals

The electron paramagnetic resonance spectra of Cu²⁺ doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) (hereafter, CdNAS) single crystals which were taken at room temperature are discussed. It was found from the analysis of the EPR data that the Cu²⁺ ions substitute for magnetically inequivalent Cd²⁺ ions. Two magnetically inequivalent Cu²⁺sites were observed. The principal values of the g and the hyperfine tensors were determined. The ground state wave functions of the unpaired electron of Cu²⁺ ions in two sites were constructed and type of the distortion was determined.     

Diabetes induces compositional, structural and functional alterations on rat skeletal soleus muscle revealed by FTIR spectroscopy: a comparative study with EDL muscle

Diabetes Mellitus (DM) is a metabolic disorder, characterized by abnormally high blood glucose levels due to decreased secretion or effectiveness in function of insulin. Having a role in carbohydrate and lipid metabolism, skeletal muscle is affected by the absence of insulin in diabetic conditions. This current study reports the application of Fourier transform infrared (FTIR) spectroscopy in the determination of macromolecular alterations in streptozotocin (STZ)-induced diabetic rat skeletal Soleus (SOL) muscles, which highlight the promise of this technique in medical research. The results revealed that DM induced several alterations in macromolecular content and structure of slow-contracting SOL muscles. In diabetic SOL muscles, a decrease in the content of lipids, proteins and nucleic acids together with an increase in lipid order was observed. The decrease in the level of unsaturation and acyl chain length of lipids demonstrated the increased lipid peroxidation in DM. There were alterations in protein secondary structure in DM with a decrease in α-helix and β-sheet content of proteins, whereas the content of aggregated β-strands increased, which is generally seen when proteins denature. Besides, the integrity of collagen molecules was found to be decreased, demonstrating the alterations in its triple helical structure in diabetic muscles. Furthermore, the same alterations mentioned above were also observed in diabetic fast-contracting Extensor Digitorum Longus (EDL) muscles. However, having a high content of mitochondria and relying on an oxidative pathway, SOL muscle was found to be more affected by DM.     

Coordinative flexibility in hydrotris(methimazolyl)borate divalent metal compounds

Three divalent closed d shell metal complexes of the hydrotris(methimazolyl)borate ligand, [Ca(mt)2].6H2O, [Ba(mt)2](H2O)2, and Hg4(mt)4Cl4, were synthesized and characterized by single crystal X-ray diffraction; the three structures reveal very different ligand binding modes for each metal ion.     

Facile peripheral modification of N-confused porphyrin

[reaction: see text] An improved methodology for the N-alkylation of the porphyrin isomer N-confused porphyrin is presented. The combination of polar solvent conditions and the use of the base Cs2CO3 affords externally modified products in high yield without separation difficulties and without the use of large excesses of alkylating reagent. The further transformation and metalation of these products provides opportunities for the construction of metalloenzyme model complexes, peptide adducts, and chromophore assemblies.     

A selective high-performance liquid chromatography method for the determination of reboxetine in bulk drug and tablets

Reboxetine is used as a selective noradrenaline reuptake inhibitor for the treatment of major depressive disorders. It is effective in the treatment of severe depression and safer to use than traditional tricyclic antidepressants. In this study, a novel, simple, and rapid stability-indicating high-performance liquid chromatography (HPLC) method for reboxetine methansulfonate was successfully developed and validated for the assay of tablets. The method was used to quantify reboxetine in tablets; it employed a C18 column (150 x 4.6 mm id) with an isocratic mobile phase consisting of methanol-phosphate buffer (pH 7, 0.02 M; 55 + 45, v/v) at a flow rate of 1.0 mL/min. Reboxetine was detected by an ultraviolet detector at 277 nm. The retention time of reboxetine was about 4.5 min. The developed HPLC method was validated with respect to linearity, precision, sensitivity, accuracy, and selectivity. The method was linear over the concentration range 1-50 microg/mL (r = 0.9999). The limits of detection and the quantitation of reboxetine were 0.1 and 0.3 microg/mL, respectively. The relative standard deviation values for intraday and interday precision were 0.78-1.01 and 1.08-1.37%, respectively. Selectivity was validated by subjecting a stock solution of reboxetine to neutral, acid, and alkali hydrolysis, as well as oxidation, dry heat treatment, and photodegradation. The peaks of the degradation products did not interfere with the peak of reboxetine. The results indicated that the proposed method could be used in a stability assay. The proposed method was successfully applied to the determination of reboxetine in tablets. Excipients present in the tablets did not interfere with the analysis.     

A note on bound for norms of Cauchy–Hankel matrices

We determine bounds for the spectral and ??_p norm of Cauchy–Hankel matrices of the form H_n=[1/(g+h(i+j))]ⁿ_i,j=1≡ ([1/(g+kh)]ⁿ_i,j=1), k=0, 1,…, n –1, where k is defined by i+j=k (mod n). Copyright © 2002 John Wiley & Sons, Ltd.