PubMed Health⌕ Search

Biomedical subjects

M D Luque de Castro

Publications and source records attributed to M D Luque de Castro.

At least 91 records · Page 5Linked to original sources
PubMed1993

Flow-through optical biosensor based on the permanent immobilization of an enzyme and transient retention of a reaction product.

A new sensor based on the twofold immobilization of a catalyst and a reaction product in an optical flow cell is proposed. The packing material of the flow cell consists of two physically distinct layers: an upper layer of controlled-pore glass (CPG) onto which the enzyme is immobilized, and a lower layer of suitable exchanger where the product of the enzymatic reaction is temporarily retained. The performance of the biosensor was tested by immobilizing peroxidase on CPG and retaining the product of the reaction between hydrogen peroxide, 4-aminophenazone, and an aniline derivative on a Sephadex resin. The sensor can be used to monitor hydrogen peroxide and any previous reaction which yields it (e.g., any reaction catalyzed by an oxidase). The biosensor was applied to the determination of hydrogen peroxide and glucose in serum. The features of the determinations (linear ranges between 10 and 200 ng/mL, and RSD values smaller than 2%), in addition to the great consistency of the results with those obtained in the clinical determination of glucose by an AACC method and analyte recoveries between 95 and 105% testify to the excellent performance of the sensor.

Biosensing Techniques↗
PubMed1993

Automated determination of peroxides in olive oil by flow injection.

A method for the determination of the peroxide value of olive oil based on flow injection principles is proposed. The method requires no pre-treatment of samples that have undergone natural or forced oxidation as the sensitivity can be accommodated over wide margins (determination range 3.4-537 mequiv kg-1). The precision of the method, expressed as relative standard deviation, ranges from 0.7 to 2.4% and the sampling frequency is 15 h-1.

Flow Injection Analysis↗
PubMed1993

Automated enzymatic determination of sodium in serum.

An automated method based on the principles of flow-injection analysis is proposed for the enzymatic determination of sodium ion in serum. The method relies on the activation of beta-galactosidase by the analyte. The features of the proposed method include linear range between 1 and 1700 mumol/L, a sampling rate of 50 samples/h, a sample volume of 50 microL, and the absence of interferences from species usually present in serum. The results obtained were consistent with those provided by widely used methods such as those based on flame spectrometry and direct potentiometry with ion-selective electrodes.

Flow Injection Analysis↗
PubMed1991

Kinetic determination of aspartate aminotransferase in human serum with a flow-injection/multidetection system.

Photometric-kinetic methods for the determination of activity of aspartate aminotransferase are proposed. The flow-injection manifold used for this purpose includes a selecting valve which allows the sample to be trapped in a closed circuit where a solid reactor housing an auxiliary enzyme and a conventional single detector allows a multipeak recording to be obtained for each sample. This record represents a typical kinetic curve from which much information can be obtained to develop fixed-time and reaction-rate methods for the determination of the analyte based on its catalytic action on the L-aspartic acid-2 oxoglutarate system. The linear range is found to be between 1 and 500 U l-1, with relative standard deviation less than 1%. The utility of the methods is illustrated by the determination of the analyte in human serum from healthy and sick individuals.

Aspartate Aminotransferases↗
PubMed1991

Determination of creatine kinase activity using a co-immobilized auxiliary enzyme reactor coupled on-line with a flow injection system.

Two flow injection methods (based on spectrophotometric and spectrofluorimetric detection) were developed for the determination of over-all creatine kinase activity. Despite the complexity of the reactions involved (both include three enzyme-catalysed steps), the manifold is very simple because the two auxiliary enzymes which catalyse the two-step indicator reaction are co-immobilized on controlled-pore glass. The features of the proposed methods (calibration ranges between 0.1 and 2.0 and 0.01 and 1.0 U l-1, relative standard deviation 0.93 and 0.53% for the spectrophotometric and spectrofluorimetric methods, respectively) allow the successful determination of the analyte activity in serum samples (recoveries better than 95-105% for both methods).

Autoanalysis↗
PubMed1991

Post-column on-line HPLC measurement of reaction rates by using an open-closed derivatizing system.

An open-closed high-performance liquid chromatography (HPLC) assembly that enables post-column derivatization of the eluates and kinetic measurements (reaction-rate methods) with enhanced sensitivity and selectivity is constructed and tested by applying it to the separation and determination of the three main creatine kinase (CK) isoenzymes in serum samples with excellent results (consistent with those provided by the standard method) and recoveries between 95 and 105%.

Chromatography, High Pressure Liquid↗
PubMed1990

Determination of alanine aminotransferase in human serum in an open-closed flow injection configuration.

Open-closed flow injection systems allow the development of methods based on multidetection by using conventional detectors. The methods proposed here for the determination of alanine aminotransferase (ALT) utilize a photometric detector included in the closed circuit, which allows one to perform fixed-time and reaction-rate measurements whose sensitivity can be increased by using the sum of the analytical signals. The methods, with determination ranges between 1 and 500 U l-1 of ALT, feature sampling frequencies up to 60 h-1. Their application to serum samples provided excellent results, with recoveries between 95 and 106% and averaging at 99.9%.

Alanine Transaminase↗
PubMed1990

Automation of pharmaceutical dissolution testing by flow injection analysis.

The different types of instruments used for monitoring pharmaceutical dissolution testing are presented. Their features and the need for automation are critically discussed. The advantages of flow injection analysis in this respect are illustrated by a variety of examples clearly showing its adaptability to the different problems posed by other automatic and non-automatic alternatives.

Autoanalysis↗
PubMed1990

Use of photochemical reactions in flow injection: determination of oxalate in urine.

The use of photochemical reactions in flow injection (FI) is reported. The irradiation of an FI reactor with a suitable source facilitates the development of the iron(III)-oxalate reaction, allowing the amperometric determination of the anion in the range 1.0-13.0 micrograms ml-1, with a relative standard deviation of 1.1% and a sampling frequency of 40 h-1. The proposed method was applied successfully to the determination of oxalate in urine samples.

Humans↗
PubMed1989

Comparison of different flow injection approaches to the automatic determination of enzymatic activity.

Three configurations based on the principles behind flow injection analysis (FIA) are proposed for the automatic determination of enzymatic activity. The proposed approaches are normal, stopped-flow and open-closed FIA. The comparative study of the methods developed from these approaches allows the establishment of the scope of the application of each, with inherent advantages and disadvantages.

Enzymes↗
PubMed1989

Development of a statistical model for predicting the ethanol content of blood from measurements on saliva or breath samples.

Blood, saliva and breath samples from a population of males and females subjected to the intake of preselected amounts of ethanol, whilst in different physical conditions (at rest, after physical exertion, on an empty stomach and after eating), were analysed by automatic methods employing immobilized (blood) or dissolved (saliva) enzymes and a breathanalyser. Treatment of the results obtained enabled the development of a statistical model for prediction of the ethanol concentration in blood at a given time from the ethanol concentration in saliva or breath obtained at a later time.

Adult↗
PubMed1989

Flow injection analysis of pharmaceuticals.

An overview of the most representative problems solved by flow injection analysis (FIA) in drug analysis is presented. Different aspects of this technique which can be manipulated with specific purposes are discussed and special emphasis is placed on the possibilities of FIA in dissolution test control.

Chemistry, Pharmaceutical↗
PubMed1987

Enzymatic determination of total cholesterol in serum by flow injection analysis.

Several methods are proposed for the enzymatic determination of total cholesterol in serum by flow injection analysis (FIA). The use of the merging-zones mode, with or without halting of the reacting plug in the photometric or fluorimetric detector, has allowed the development of four precise methods for the determination of this analyte; calibration curves were linear for ranges of 0.02-0.2 and 0.005-0.05 gl(-1). These methods have been applied to the determination of cholesterol in serum with excellent results.

Journal Article↗