Direct Determination of Glucose in Blood Serum Using Trinder's Reaction

Abstract

A very simple flow injection analysis system for direct determination of glucose in blood serum based on Trinder's reaction is described. The sera samples (15 μl) can be injected directly to the system without the deproteinization or the use of a dialyzer.

Calibration curves are linear in the range 50–400 mg/dl. The sampling frequency is 60 samples per hour. Results obtained by the proposed procedure are compared with those acquired at a local hospital using their routine glucose procedure also based on Trinder's reaction. It is shown that a better mix between sample and reagents is achieved using the single bead string reactor (SBSR).     

A Fast Made Disposable Glucose Biosensor Incorporating the Oxidase and a Ferrocene in an Alginate Gel

Abstract

A simple procedure is described for co-immobilization of glucose oxidase and dimethylaminomethylferrocene in a sodium alginate gel on the surface of pyrolytic graphite electrode. The film is electrochemically active and the peak current is a function of D-glucose concentration with the apparent Michaelis-Menten constant K_m = (1.2±0.3) × 10^?2 M. The optimal concentration range for biosensoric applications in 0.001–0.010 M.

     

Improved Blood Compatibility at a Glucose Enzyme Electrode Used for Ejctraoorpokeal Monitoring

Abstract

A glucose enzyme electrode based on glucose oxidase has been used in an extracorporeal flow system which allows standardization during monitoring. The detection limit for glucose was 0.02 mmol/l, and the linear range, which extended to 5 mmol/l glucose, allowed measurement of whole blood after dilution. Restandardization following whole blood exposure led to a loss of sensitivity which was attributed to coating of electrode membranes by blood constituents. The problem was largely overcome through use of silane-treated membranes and the operation of electrodes in a narrow channel flow cell.     

Enzyme-Induced Chemiluminescence-Determination of Blood Glucose Using Luminol

Abstract

Hydrogen peroxide, produced by the interaction of glucose with immobilized glucose oxidase, reacts with the ferricyanide-luminol system to produce chemiluminescence linearly proportional to glucose concentration. The coupled reaction is used as a sensitive precise micro method for the determination of true blood glucose. The linear range of detection is 10^?7 - 10^?4 M glucose. The method correlates quantitatively with two glucose reference techniques.     

A Split-Flow Enzyme Thermistor

Abstract

The split-flow system is comprised of two identical micro-columns, one of which contains an immobilized enzyme preparation, the other an inert support material.

The heat produced in each column on introduction of a sample is measured with thermistors placed in these columns. The use of a reference column virtually eliminates the influence on the measurements of artifactual signals as unspecific heat, i.e., heat not produced by the enzymic reaction. The performance of the split-flow enzyme thermistor at a variety of pH's, ionic strengths or viscosities associated with the sample has been investigated and compared with previously described alternative enzyme thermistor arrangements. In this comparative study glucose at a concentration of 5 · 10^?4 M was used throughout. On passage through the imnobilized glucose oxidase preparation this solution gave rise to a heat change At of about 0.01°C. The insensitivity of the system described herein towards such variations makes it particularly suitable for the analysis of metabolities present in crude solutions such as urine and skim-milk.     

Amperometric Sensor and Immobilized Enzyme Electrode for the Determination of Enzymatic Activities

Abstract

A sensitive method for the rapid determination of activities of soluble or immobilized enzymes, based on the electrochemical detection of hydrogen peroxide is described. Kinetic studies (Vmax and K_M determinations) can be performed for all H₂O₂ generating enzymes (i.e. most of the oxidases) using an amperometric probe with a platinum anode at a fixed potential.

When associated with an immobilized glucose oxidase membrane, this sensor constitutes a glucose electrode and the activity of any hydrolase which releases glucose can be measured. There is no need for other auxiliary enzymes and no preincubation step is required. The possibility to carry out continuous analysis constitutes the main advantage of the described method.     

Glucose Monitoring by a Biosensor Based on Mercury Thin Film Electrodes

Abstract

Mercury film electrodes consist of a thin film of mercury deposited on an electrode surface (typically glassy carbon) by reduction of a mercury (II) salt in solution. The surface area/volume ratio is larger for the mercury film electrode, and this electrode is more stable than mercury drop electrode, which allows a faster stirring rate to be used in the deposition step. An enzyme electrode is described, based on glucose oxidase immobilized by gelatin and glutaraldehyde and held over a glassy carbon electrode coated with a thin mercury film. This biosensor responds fast and linearly to glucose in a wide concentration range, which is significant because monitoring of glucose levels is a critical component of diabetes care. Certain optimization and characterization studies were carried out. Average value, standard deviation (SD), and variation coefficient (CV) were calculated with the help of the repeatability studies. Finally, glucose content of human blood samples was monitored with the help of the biosensor presented.     

Determination of Some Phenothiazine Drugs Based on Colour Reaction with Potassium Periodate

ABSTRACT

A simple, rapid and sensitive method for the determination of six phenothiazine drugs, either in pure form or in pharmaceutical formulations, is described. The method is based on the formation of stable phenothiazine free radical by the use of potassium periodate as the chromogenic reagent in sulphuric acid medium. The reaction is suggested to proceed via oxidation of the phenothiazine nucleus into a semiquinonoid radical. The wavelengths of maximum absorption range from 500 to 525nm. Molar absorptivities range from     

A Gas Chromatographic Assay for the Tetracyclic Antidepressant Maprotiline in Blood,Using Electron-Capture Detection

Abstract

A procedure is described which permits the determination of maprotiline in biological fluids for concentrations in the range of 10 to 1000 ng/ml. It relies on the use of N-desmethylclomipramine as internal standard, on derivatization of the secondary amines with heptafluorobutyric anhydride, and the use of gas chromatography with electron-capture detection. The method is linear, specific, accurate and precise. It is suitable for routine analyses and is particularly applicable for monitoring the levels of maprotiline in the blood of patients treated for depressive illness.     

Highly Selective and Sensitive Amperometric Biosensing of Glucose at Ruthenium-Dispersed Carbon Paste Enzyme Electrodes

Abstract

The selectivity and sensitivity of glucose measurements at carbon-paste based amperometric biosensors are greatly enhanced through the use of ruthenium-dispersed graphite particles. The improved performance is attributed to the substantial lowering of the overvoltage for the reduction of the hydrogen peroxide product. Hence, cathodic measurements of glucose can be caried out at an optimal potential range (-0.15 to +0.20 V). Contributions from easily oxidizable substances (e.g. acetaminophen, ascorbic and uric acids) are eliminated, without the need for mediators or membrane barriers. The electrocatalytic action of the ruthenium sites results also in a substantially improved sensitivity. A fast flow injection operation is illustrated.     

Flow-Injection Determination of Glucose by a Photoinduced Chemiluminescent Reaction

Abstract

A flow-injection procedure for the photochemical determination of glucose has been developed. The method is based on the photo-oxidation of glucose sensitized by 9,10-anthraquinone-2.6-disulfonate (disodium salt). The hydrogen peroxide formed in the photochemical reaction was measured by means of the chemiluminescent reaction with luminol and hematin. A linear calibration graph was obtained over the range 2.0x10^?6-8.5 x 10^?5 mol L^?1. The method was applied to determining glucose in blood serum, urine and fruit juices.     

Measurement of glucose using fluorescence quenching

A new spectroscopic procedure for the measurement of glucose concentrations is described which is based on substrate induced quenching (SIQ) of an indicator fluorescence. The method exploits a novel photo reaction between thionine and NADH, the latter being generated due to the reduction of NAD⁺ in an enzymic reaction between glucose dehydrogenase (GDH) and glucose. The observed SIQ data was analysed using an empirical relation. A quenching constant of 1.8×10³ (±100) M⁻¹ is obtained for the substrate induced quenching of thionine by glucose. The reported method, which was investigated over the range 0–1000 μM, offers a glucose detection limit of 2.2 μM. Various applications of the proposed scheme are discussed, including its use to construct a fibre optic biosensor for glucose.     

A Novel Enzyme Membrane Electrode for Oxalate Determination in Foodstuffs

Abstract

An enzyme membrane electrode usable for the assay of oxalate in foodstuffs is described. A commercially available preactivated polyamide membrane was used for the immobilization of oxalate oxidase. The bioactive disk thus obtained was associated with an amperometric transducer. The resulting self-contained enzyme electrode wich allows oxalate determination in various materials with minimal pretreatment exhibits a linear calibration ranging from 10–7 M and 10–4 M in the cell. The response-time was comprised between 20 seconds and 1 minute, depending on the oxalate content in the sample. The electrode-response was very stable for at least 4 months, a period during which more than 150 assays were performed.

The results obtained with several food materials were in good agreement with those obtained with the conventional spectrophotometric method. Assays were also performed with a microprocessor-based analyzer normally used for glucose measurements with a glucose oxidase electrode When the analyzer is equipped with an oxalate oxidase membrane, without further setting, oxalate can be determined in the range 5 10^?3 M-10^?1 M in the sample.     

Preparation of Novel Macroporous Silica-Based Amide-Polymer-Bonded Packing and Its Application to the Separation of Proteins

ABSTRACT

A novel silica-based amide-polymer-bonded packing to be used for protein separation is described. A macroporous silica support was bonded with diethoxymethylvinyl silane, and then copolymerized with methylacrylamide and divinylbenzene to produce a tailored stationary phase. This packing has high resolution and stability in a large pH range; it was characterized through the separation of a standard protein mixture containing bean trypsinogen inhibitor, glucose oxidase, ribonuclease and pepsin. Such manipulation of the proteins elution profile is achievable in less than 12 minutes. The effect of pH on the protein separation is discussed, as is the effect of ammonium sulfate concentration. It is suggested that the macroporous silica-based amide-polymer-bonded packing is a better alternative for the biopolymer separation.     

Spectrophotometric Method for the Estimation of Vitamin C in Drug Formulations

Abstract

The use of 1-chloro-2, 4-dinitrobenzene is described for spectrophotometric estimation of ascorbic acid. The procedure is based on the interaction of ascorbic acid with 1-chloro-2, 4-dinitrobenzene in alkaline medium. The product absorbs maximally at 380 nm and has the molar absorptivity 0.14 × 10⁴1 mole^?1cm^?1. Beer's law is obeyed in the concentration range 0.12–0.6 mg/10ml of ascorbic acid.     

Simultaneous Determination of Valsartan and Hydrochlorothiazide in Tablets by High-Performance Liquid Chromatography

ABSTRACT

A method for the simultaneous determination of valsartan and hydrochlorothiazide in tablets is described. The procedure, based on the use of reversed-phase high-performance liquid chromatography, is linear in the concentration range 5.0-10.0 μg ml^?1 for valsartan and 0.5-2.0 μg ml^?1 for hydrochlorothiazide, is simple and rapid and allows accurate and precise results. The limit of detection was 1.0 μg ml^?1 for valsartan and 0.05 μg ml^?1 for hydrochlorothiazide.     

Selective Liquid and (Vinyl-Chloride) Pentoxyverine Membrane Electrodes - Their Preparation and Use for the Potentiometric Determination of Pentoxyverine Citrate

Abstract

The use of liquid and poly(vinyl-chloride) membrane electrodes which are sensitive and reasonably selective for pentoxyverine determination is described here. The electrodes are based on the use of pentoxyverine-picrate, pentoxyverine-picrolonate and pentoxyverine-tetraphenylborate ion association complexes as electroactive materials in nitrobenzene or in poly(vinyl chloride) matrix. These electrodes show near Nernstian response values in different concentration ranges, depending on the nature of the used counter-ions, at 3.3–7.8 pH range. Potentiometric determination of pentoxyverine citrate with use of these electrodes gives good results which later on are compared with those obtained by non-aqueous titration.     

An Enzyme Biosensor for Rapid Assay of Glucosinolates

Abstract

A novel electrochemical method for analysis of glucosinolates is described. Glucose, released by the action of myrosinase on the analyte, is detected amperometrically by a glucose electrode having glucose oxidase immobilised on a platinised carbon base. The dependence of current responses on analyte concentration was linear up to 5mM for sinigrin and progoitrin, and the applicability of the method for determination of total glucosinolate in rape seed was demonstrated. An alternative approach was also examined which employed a bi-enzyme electrode made by co-immobilising the two enzymes on the same electrode.     

An Optical Fibre Probe for the Determination of Glucose Based on Immobilized Glucose Dehydrogenase

Abstract

An optical fibre probe based on glucose dehydrogenase immobilized on nylon was constructed. The probe was used to quantitate glucose through a measurement of the fluorescence of the NADH formed by the enzyme-catalyzed reduction of glucose in the presence of NAD. The probe response was reproducible and displayed good linearity in the concentration range of 1.1 to 11.0 mM glucose. The limit of detection was 0.6 mM glucose. The response was affected by pH and NAD concentration.     

Glycosylhydrazides,a New Class of Sugar Surfactant. Preparation and Amphiphilic Properties of 1-Glycosyl-2-Acylhydrazines

ABSTRACT

The synthesis and the amphiphilic properties of 1-glycosyl-2-acylhydrazines are described. This new class of surfactants, referred to as glycosylhydrazides, is easily available from a reducing sugar and hydrazides without protection. Seven hydrazides having an alkyl chain of up to fourteen carbon atoms, are coupled with glucose giving 1-glucosyl-2-acylhydrazines in good yields; 1-maltosyl-2-octanoylhydrazine, as a typical disaccharide-based surfactant, is prepared as well. Critical micellar concentrations of these surfactants range from 0.04 to 252 mM.