摘要:

A micro enzyme-sensor using uricase (EC 1.7.3.3) was developed for measuring uric acid. For this, a sheet of porous composite was made from acetylene black and Teflon emulsion and was soaked in Zonyl FSN fluoro-carbon surfactant and Nafion. The 50 μ m platinum micro-electrode was etched in hot aqua regia to create a cavity at its tip and this cavity was packed with porous composite material by pushing the tip into small lumps of the material. The redox mediator [Os(bpy)3(PF6)2] was monitored by cyclic voltammetry. The porous micro-sensor was dipped overnight in Tris-hydrochloric acid buffer of pH 8.0 containing enzyme for adsorption of uricase at 4°C. The effects of pH, and temperature on measurements of uric acid with the sensor were examined, the calibration curve for measurement of uric acid under optimum conditions was determined and the effect of concomitant compounds were investigated. Under optimum conditions, the response of the micro-sensor was linear in the concentration range of 0.101 - 1.93mM uric acid. The uric acid concentrations in commercial preparations and human serum were also determined with this sensor.

ISSN:0003-2719    

DOI:10.1080/00032719408006342

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A flow-through system for the determination of glutathione was developed using the enzyme glutathione oxidase covalently immobilized on an Immobilon AV membrane assembled on a Clark type oxygen electrode. A calibration curve for glutathione was obtained in the range 10−5- 10−3mol/L with a detection limit of 5.10−6mol/L and a relative standard deviation of 4.5%.

ISSN:0003-2719    

DOI:10.1080/00032719408006343

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The detection of organophosphate and carbamate pesticides using amperometric biosensors based on immobilized cholinesterases (ChE) was investigated. If only one type of ChE was used for analysis, the sensitivities for some pesticides were not sufficient. We have prepared biosensors with immobilized acetylcholinesterase or butyrylcholinesterase and with both ChEs coimmobilized in the same enzyme layer. Both coimmobilized ChEs function simultaneously in the presence of acetylthiocholine and these biosensors exhibit high response to a wider group of pesticides compared with sensors containing only one type of ChE.

ISSN:0003-2719    

DOI:10.1080/00032719408006344

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Highly sensitive spectrophotometry for polyphenols has been proposed based on amplified pH changes during the substrate recycling of polyphenols driven by tyrosinase and L-ascorbic acid, which can be monitored as a spectral change in BTB (bromothymol blue). Polyphenolic compounds are enzymatically oxidized too-quinone compounds catalyzed by tyrosinase, and are chemically regenerated by L-ascorbic acid, followed by substrate recycling. During this cyclic redox reaction, the pH continuously increases because a proton in the solution is consumed wheno-quinones react with L-ascorbic acid. The magnitude of this pH change is significantly dependent on the concentration of the polyphenols, so a highly sensitive determination was possible by monitoring the absorbance of BTB in the enzyme solution with a reaction time of 5-10 min. The detection limits of catechol and catecholamines (L-dopa, dopamine, noradrenaline and adrenaline) were found to be on the order of 1x10−7M-1x10−9M using tyrosinase (catechol oxidase activity; 350 U ml−1), 1x10−2M L-ascorbic acid and 0.005 % BTB.

ISSN:0003-2719    

DOI:10.1080/00032719408006345

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A rapid and sensitive high-performance liquid chromatographic (HPLC) assay has been developed for the determination of metoclopramide in plasma. The assay is performed after single extraction of metoclopramide and diazepam (internal standard) from alkalinized plasma into ether and eluted from a Nova Pak C18-column with a mobile phase composed of acetonitrile:water (55:45%, v/v) adjusted to pH 3. The column eluent was monitored at 273 nm. Measurement was achieved by taking the peak-height ratios of the drug to the internal standard. The detection limit for metoclopramide in plasma is 5 ng/ml. Within-day coefficients of variation (CVs) ranged from 3.05 to 4.43% and between-day (CVs) from 4.1 to 5.7% at three different concentrations. Preliminary stability tests showed that metoclopramide is stable for at least 3 weeks in plasma after freezing. The method is applied for the determination of the pharmacokinetic parameters of metoclopramide after administration of two tablet formulations, to 4 healthy male volunteers.

ISSN:0003-2719    

DOI:10.1080/00032719408006346

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A stability-indicating, specific, sensitive and validated reversed-phase HPLC assay for paracetamol, guaiphenesin, sodium benzoate and oxomemazine in the presence of degradation products, i.e. 4-aminophenol and guaicol, as well, as the co-formulated adjuvants and 5-hydroxymethylfurfural, a commonly formed compound in syrups during formulation and/or storage of pharmaceutical syrups, has been developed to allow simultaneous determination of these compounds in a cough syrup. The HPLC method includes the use of a two-line solvent delivery system. The specificity, precision in term of both repeatability (i.e. intraday precision) and reproducibility (i.e. interday precision), limit of detection of the degradation products and ruggedness due to column to column batch and source variation have been discussed. The developed method has been applied for the determination of the main drugs and their degradation products in freshly prepared as well as in stored samples of cough syrup.

ISSN:0003-2719    

DOI:10.1080/00032719408006347

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A sensitive spectrophotometric method for zinc has been established by reacting zinc with three salicylic acid azo dyes 2-hydroxy (Ia), 2-carboxy (Ib) and 4-(2-arsonophenylazo) salicylic acid (Ic) in universal buffer solution of pH 8.4, 7.1 and 6.0 respectively. The molar absorptivities are 1.16, 1.39 and 1.36 X 1041/mol.cm at 515, 450 and 525 nm using reagents Ia, Ib and Ic respectively. The formed complexes have the molar ratios of zinc to ligands 1: 1 and 2: 1. Beer's law is obeyed upto 7.19 ppm of zinc whereas the optimum concentration range as evaluated by Ringbom's method is 0.5-7.00 ppm. Sandell sensitivities of the method are evaluated. The method has been used to determine zinc in various pharmaceutical products.

ISSN:0003-2719    

DOI:10.1080/00032719408006348

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Simple and sensitive spectrophotometric methods are described for the determination of ketorolac tromethamine based on charge-transfer and ion-pair complexation reactions. In the first method the drug was reacted with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or with 2,4-dichloro-6-nitrophenol (DCNP) in methanol. The colour formed due to the formation of charge transfer complex showed maximum absorbance at 392 nm and 425 nm respectively and linearity in the range 10-80 μg.ml−1. In the second method ketorolac tromethamine was treated with reagents, viz. methylene blue (MB) or saframine (SF), in the presence of phosphate buffer. The ion pair complexes were extracted into chloroform and the absorbance was measured at 640 nm and 515 nm respectively. Beer's law was obeyed in the range of 5-50 μg.ml with both the reagents.

ISSN:0003-2719    

DOI:10.1080/00032719408006349

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The use of on-site anodic stripping voltammetry (ASV) to monitor and evaluate the effectiveness of copper-based algicide dosing of a reservoir is presented. An initial comparison of the copper levels determined by anodic stripping voltammetry (ASV) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) was performed in the laboratory using 46 water samples collected during an algal control treatment of a reservoir. Good correlation was observed at the 95% confidence limit. Use of ascorbate as oxygen scavenger in chloride media was found effective for copper determination in the field by ASV. The ascorbate-chloride electrolyte removes the need for inconvenient nitrogen or argon bubbling for oxygen removal. ASV monitoring was used to monitor algicide dosing operations by boat and aircraft. Data during the first 60 minutes of dosing is presented at surface, 5 and 10 metre depths.

ISSN:0003-2719    

DOI:10.1080/00032719408006350

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A new spectrofluorimetric method for the determination of magnesium with 1,2,4-trihydroxyanthraquinone in a 90:10 ethyleneglycol-water medium of pH 9.15 provided by an ammonia/ammonium chloride buffer was developed. The proposed method allows the determination of 1-50 ng/ml magnesium and features a detection limit of 0.2 ng/ml. The effect of potential major interferences was investigated and the method was successfully applied to the determination of magnesium in various types of water collected on Tenerife island as well as in blood serum.

ISSN:0003-2719    

DOI:10.1080/00032719408006351

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor