Diphasic dialysis extraction technique for clenbuterol determination in bovine retina by gas chromatography-mass spectrometry

Summary A method is described for the extraction of clebuterol from bovine retina samples by diphasic dialysis using gas chromatography—mass spectrometry (GC-MS) as the procedure of determination. Following chemical digestion of retinal tissue in alkaline medium at 80°C, clenbuterol is extracted by diphasic dialysis using diethyl ether as solvent at 37°C, for 4 h at 150 rpm. Diethyl ether is evaporated to dryness and clenbuterol determined by GC-MS after butylboronic acid (BBA) derivatization. A detection limit of 2.5 ng g⁻¹, repeatability of 9.0% and reproducibility of 22.9%, with recoveries always >86% (n=5), are achieved as validation criteria.     

Electric Field Enhancement of Donnan Dialysis

Abstract

Donnan dialysis of cations into simple receiver electrolytes such as NaNO₃ is inhibited by interaction between the fixed sulfonate exchange sites on the cation exchange membrane and the test cations. Application of a 5 V cm^?1 (peak-to-peak) sine wave at 1 MHz across the membrane diminishes the retardation and allows the Donnan dialysis rate to approach the diffusion limit with Cd, Cu, and Zn test metals and a 0.1 M NaNO₃ receiver. The transport to Pb is still retarded by about 25%. The use of 0.2 M Mg(II), 0.5 mM Al(III) receiver results in diffusion limited transport for all metals.     

Fluorimetric Determination of Aluminium Traces (ppb) in Hemodialysis Solutions Using Morin and Pontachrome Blue Black

Abstract

Two simple procedures for spectrofluorimetric microdosage of Al in dialysis fluids using Morin and Pontachrome Blue Black (PBB) dyestuffs are described. The optimum experimental conditions for both the fluorimetric reagents and for the particular kind of matrix are reported. Linearity between emission intensity and Al concentration was observed in the range 5–50 ppb for PBB and 2–30 pbb for Morin respectively. The Al amount was determined by applying the standard addition method. Both the spectrofluorimetric reagents proved to be suitable for sensitivity and accuracy to Al determination in dialysis fluids.     

Binding equilibrium study of phosphotungstic acid and HSA or BSA with UV spectrum, fluorescence spectrum and equilibrium dialysis

The binding equilibrium between phosphotungstic acid (H7[P(W2O7)6] · XH2O;PTA) and human serum albumin (HSA) or bovine serum albumin (BSA) has been studied by UV-Vis, fluorescence spectroscopies and equilibrium dialysis. It has been observed that UV absorption enhanced and the fluorescence quenched as the PTA binding to HSA or BSA at physiological pH 7.43(?.02). The Scatchard analysis indicated that there exists a strong binding site of PTA in both HSA and BSA, and the successive stability constants of these two systems are obtained by nonlinear least-squares methods fitting Bjerrum formula.     

Glutathione Peroxidase‐Based Amperometric Biosensor for the Detection of S‐Nitrosothiols

A new biosensor is described for the detection of S‐nitrosothiols (RSNOs) based on their decomposition by immobilized glutathione peroxidase (GPx), an enzyme containing selenocysteine residue that catalytically produces nitric oxide (NO) from RSNOs. The enzyme is entrapped at the distal tip of a planar amperometric NO sensor. The new biosensor shows good sensitivity, linearity, reversibility, and response times towards various RSNO species in PBS buffer, pH 7.4 . In most cases, the response time is less than 5 min, and the response is linear up to 6 μM of the tested RSNO species. The lowest detection limit is obtained for S‐nitrosocysteine (CysNO), at approx. 0.2 μM. The biosensor's sensitivity is not affected by the addition of EDTA as a chelating agent; an advantage over other potential catalytic enzymes that contain copper ion centers, such as CuZn‐superoxide dismutase and xanthine oxidase. However, lifetime of the new sensor is limited, with sensitivity decrease of 50% after two days of use. Nonetheless, the new amperometric GPx based RSNO sensor could prove useful for detecting relative RSNO levels in biological samples, including whole blood.     

Evaluation of partition coefficients of low molecular weight solutes between water and micelles of block copolymer of ethylene oxide based on dialysis kinetics and fluorescence spectroscopy

 Application of micelle-forming surfactants in various fields of technology and use of micelles as carriers for drug targeting requires simple evaluation of partitioning coefficients of different solutes between water solution and micellar microphase. A number of methods of partitioning evaluation have been already proposed, but most of them are applicable only for fluorescent dyes or require complicated and expensive equipment, such as NMR spectrometers. In the present work two methods of the molar fraction of solubilized material determination are compared. One of the techniques used is based on the changes in fluorescence spectra during solubilization. The other approach is based on the dialysis slowing down, which occurs if the solute is associated with large particles (e.g. micelles). Graphic method of partition coefficient (P) evaluation is proposed and P values of a widely used anti-tumor drug doxorubicin and highly hydrophobic fluorophore perylene are determined. The comparison shows that the results of both methods give very close coincidence. The solubilization data were used for the calculation of the important parameter – the ratio of micelle volume to aggregation number, which makes sense of packing density of the detergent molecules in the micelle. The comparison of this parameter calculated from the solubilization data with that obtained from light scattering experiments is discussed. It is assumed that the dialysis technique could be used for partitioning evaluation of all substances, which may be detected in solution. Received: 15 September 1997 Accepted: 3 November 1997     

Native and Hydrolyzed Fibroin of Natural Silk Modified Mechanochemically by Benzimidazolyl-2-methylcarbamate Hydrochloride

Native and hydrolyzed fibroin of natural silk modified by benzimidazolyl-2-methylcarbamate hydrochloride was studied using IR spectroscopy, electron-microscopy, X-ray structure analysis, solubility, and dialysis. Mechanical treatment of a mixture of native and hydrolyzed fibroin of natural silk with benzimidazolyl-2- methtylcarbamate hydrochloride in a 2:1 ratio was shown to form inclusion complexes.     

Rapid Determination of Hydrogen Peroxide in Milk with Non-enzymatic Amperometric Sensor Based on Porous Gold Modified Screen-printed Electrode in Online Dialysis System

A rapid method for determination of hydrogen peroxide based on a non-enzymatic amperometric sensor with an online dialysis unit was developed for analysis of sample with complicated matrices. A porous gold modified gold screen-printed electrode was prepared by a simple method using 9 V-battery electrodeposition. Based on data from amperometry, a linear dynamic range can be obtained in the range of 10 to 1000 μmol L⁻¹, with a limit of detection of 0.37 μmol L⁻¹. The proposed system was successfully applied to determine H₂O₂ in various milk samples with rapid analysis, high electrode stability, and excellent repeatability (1.95 % RSD with 100 replications).     

尿毒症患者血清中中分子物质的提取及性质的初步表征

从尿毒症患者血清及腹透液中得到的中分子量物质,具有相同的凝胶色谱行为及紫外、红外吸收行为,它们在206和235nm处,有特征紫外吸收峰;在波数为3246,1516,1122和613cm~(-1)处,有特征红外吸收峰。中分子物经离子交换色谱进一步分离,发现起决定紫外及红外吸收行为的成分集中于第3子峰;其自由氨基酸和肽类物质含量均低于3％。     

In‐depth insight into the methods of plasma protein‐drug interaction studies: Comparison of capillary electrophoresis‐frontal analysis,isothermal titration calorimetry,circular dichroism and equilibrium dialysis

Plasma protein‐drug binding assays are routinely performed during the early stages of drug discovery and development, which creates demand for an automated high‐throughput screening assay to increase laboratory efficiency. A comprehensive comparison of the four methods typically used for determining the binding parameters is presented in this study with respect to the above demand. Capillary electrophoresis‐frontal analysis, isothermal titration calorimetry, circular dichroism and equilibrium dialysis were used to study the affinity of human serum albumin for diclofenac and lidocaine. These model drugs were chosen due to their different physico‐chemical properties and different binding sites on the albumin molecule, also resulting in different binding strength. The binding parameters estimated under the conditions as similar as possible were comparable among all these approaches as well as to the literature values. Besides this, the comparison of the results and especially other considerations demonstrated the benefits and drawbacks of the selected methods, with capillary electrophoresis‐frontal analysis being the best candidate for such studies.