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At least 91 records · Page 5Linked to original sources
PubMed1990

Simultaneous determination of glucose, ethanol and lactate in alcoholic beverages and serum by amperometric flow injection analysis with immobilized enzyme reactors.

Glucose, ethanol and lactate were determined simultaneously in a flow injection system by using a parallel configuration of immobilized enzyme reactors. Hydrogen peroxide produced was monitored amperometrically at the potential of +0.65 V vs. Ag/AgCl. Linear relations between sensor responses and each species were observed in the ranges of 0.02-10 mM (glucose), 5 x 10(-4)-0.1% (v/v) (ethanol) and 0.005-1 mM (lactate) with correlation coefficients larger than 0.999 for each species. The relative standard deviations for 10 successive injections were 1.4, 0.5 and 1.1% for glucose (1 mM), ethanol (5 x 10(-3)% (v/v] and lactate (0.05 mM), respectively. Analysis of serum samples was performed with urate-eliminating reactors which were set just before each immobilized enzyme reactor. Interference of ascorbate in a serum sample was completely eliminated by using an ascorbate-eliminating reactor which was set before the sample injection valve. Application of the system to alcoholic beverages and control serum was described and the results were compared with those of free enzymatic, spectrophotometric analysis (F-kit or C-test method).

Alcoholic Beverages↗
PubMed1991

[Solvent extraction-flow injection analysis for determination of trimethoprim in compound preparations].

Trimethoprim (TMP) in four pharmaceutical preparations (compound sulfamethoxazol tablets, compound tetracycline tablets, compound trimethoprim and sulfamethoxazol tablets; and compound berberine injection) is determined by solvent extraction-flow injection spectrophotometry. It can be extracted into chloroform directly, and the absorbance at a wavelength of 280 nm of the organic phase is measured after phase separation. The manifold comprises two streams. The sample is injected into a 0.2 mol/L NaOH carrier stream, and extracted with chloroform in a 200-cm coil (ID 0.7 mm) after a 50 cm reaction tube (ID 1.0 mm). Calibration graph is linear in the range of 25-150 micrograms/ml. The average recovery is 101.4% with a relative standard deviation of 1.1%. The proposed system permits the analysis of about 50 samples per hour. Precise results in agreement with those obtained with official methods are achieved.

Drug Combinations↗
PubMed1990

Competitive heterogeneous enzyme immunoassay for theophylline by flow-injection analysis with electrochemical detection of p-aminophenol.

A competitive enzyme-linked immunoabsorbent assay based on the flow-injection amperometric detection of p-aminophenol has been investigated with use of the materials and general procedure of a commercial kit for the determination of theophylline in human serum. The antibody is immobilized on glass beads, and the enzyme label is alkaline phosphatase (EC 3.1.3.1). The high currents generated during the electrochemical detection allowed a rapid (35 min) and simple determination of theophylline throughout its therapeutic range (10-20 mg/L) and also in the subtherapeutic range (detection limit of about 80 micrograms/L).

Aminophenols↗
PubMed1987

Measurement of protein using flow injection analysis with bicinchoninic acid.

We have used the bicinchoninic acid reagent developed by Pierce Chemical Co. to measure proteins in a simple flow injection analyzer. The sensitivity is comparable to that of the Lowry method and no pipetting of reagents is needed. Results are obtained in less than 1 min and samples may be run at a rate of 60/h. The response is linear over a range of protein concentration (0-10 micrograms) and sample size (5-20 microliters) convenient for most analytical requirements. A peristaltic pump, a controlled-temperature water bath, and a spectrophotometer with flow cuvette are the only special apparatus required.

Proteins↗
PubMed1991

[Determination of tetracyclines by flow injection analysis].

An accurate, convenient and fast method was proposed for the determination of tetracyclines (tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline) and their preparations by flow injection detector based on tetracycline flow-through sensor. The parameters affecting the measurement were discussed. The detector can respond to tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline, at the same time. Their slopes are 51-55 mV/decade over the concentration range of 10(-2)-5 x 10(-5) mol/L at pH 1.5-3.5. The results obtained are in good agreement with those by biological assay (less than 3% deviation). One hundred samples can be determined in an hour.

Electrochemistry↗
PubMed1990

Flow-injection analysis of amino acids and their metabolites by immobilized vitamin B6-dependent enzymes. Sensitive determination of L-aspartate, L-glutamate, 2-oxoglutarate, and oxaloacetate.

Sensitive flow-injection analyses of aspartate, glutamate, 2-oxoglutarate, and oxaloacetate were developed. The analytes were enzymatically coupled with NADH which was monitored by light emission from immobilized bacterial bioluminescence enzymes. Aspartate (or oxaloacetate) was assayed on the basis of NADH consumption by introducing the sample through a coimmobilized aspartate aminotransferase-malate dehydrogenase column. The assay responded linearly from 100 pmoles to 5 nmoles per assay. Glutamate (2-oxoglutarate) was determined by formation of NADH in the glutamate dehydrogenase reaction. The measuring range for glutamate was from 10 pmoles to 100 nmoles per assay. The precision of the flow-injection method was generally excellent, and the sensitivities of the described assays were 100-1000-fold higher than with spectrophotometric methods. The immobilized enzyme preparations were stable for several months in storage, and the enzyme columns could be used for 600-800 analyses. Flow-injection analyses of amino acids and related compounds by NADH/bioluminescence-coupled reactions provide a sensitive, fast, and inexpensive assay method for a wide variety of purposes.

Animals↗
PubMed1987

Determination of total cholesterol in serum by flow injection analysis with immobilized enzymes.

Several photometric and fluorimetric methods are proposed for the determination of cholesterol by use of enzymes immobilized on controlled-pore glass and the normal and stopped-flow injection modes, achieving linear ranges of the calibration curves between 26-776 mumol/l and 5-265 mumol/l with excellent regression coefficients and good coefficients of variation. The methods have been applied to the determination of this analyte in serum with excellent results.

Cholesterol↗
PubMed1989

Automated fluoroimmunoassay of theophylline and valproic acid by flow-injection analysis with use of HPLC instruments.

For automated determination of theophylline and valproic acid by use of Ames' fluoroimmunoassays we used a high-pressure liquid-chromatographic system consisting of a pump, a robotic unit (Gilson 231/401, to prepare and inject the samples into the flowing carrier), and a fluorometer with a 10-microL flow cell. Results correlated well with those of conventional liquid- and gas-chromatography (r less than 0.96). The between-run CV is about 5%. In comparison with the manual method, the volume of reagents (and thus the cost per analysis) was decreased by eightfold.

Autoanalysis↗
PubMed1990

A flow injection analysis system involving immobilized NADH oxidase in column form for clinical analysis.

A highly sensitive FIA system for chemiluminometric determination of reduced coenzyme, NADH, was developed, using immobilized NADH oxidase from Brevibacterium ammoniagenes. The enzyme catalyzed the oxidation of NADH generating hydrogen peroxide which emitted chemiluminescence when mixed with luminol and potassium ferricyanide. The immobilized enzyme reactor was a mini-column, measuring 1 or 2 mm in inner diameter and 20 mm in length, and the sample volume was only 1 microliter per assay, with a feeding speed of one sample per min and a lowest detection limit of 10 pmol NADH. A FIA system was also developed for the determination of magnesium in human serum, using an enzyme column reactor with simultaneously coimmobilized hexokinase, D-glucose-6-phosphate dehydrogenase, and NADH oxidase. The performance of the system was as satisfactory as a routine colorimetric assay, but with much higher sensitivity.

Colorimetry↗
PubMed1989

Rapid-scan hydrodynamic voltammetry and cyclic voltammetry of pharmaceuticals in flow injection analysis conditions.

An on-line rapid-scan electrochemical detector is described for HPLC and FIA systems. Its practical use in qualitative analysis is demonstrated for 19 drug substances. The detector can be operated to record convection/diffusion-controlled (S-shaped), or diffusion-controlled (peak-shaped) voltammograms. In the latter mode, on-line cyclic voltammetry measurements are possible. The cell can also be used as an amperometric detector for conventional, microbore and micro-LC methods. Detection limits are of the order of 10 pg (conventional and microbore HPLC), or at the sub-picogram level (micro-LC). For scanning work, drugs can be analysed at mg l-1 levels in an FIA setup.

Caffeic Acids↗