4 research outputs found
A Stable Glutamate Biosensor Based on MnO2 Bulk-modified Screen-printed Carbon Electrode and Nafion(R) Film-immobilized Glutamate Oxidase
No full textAn amperometric glutamate biosensor was developed using screen-printed carbon electrodes bulk-modified with MnO2 (5%, m:m) onto which glutamate oxidase was immobilized via Nafion(R) film entrapment. The analytical performance of the biosensor was assessed in a flow injection mode and peak heights of the current response were used to evaluate results. Best responses were recorded at an applied potential of 440 mV (vs Ag/AgCl) a flow rate of 0.2 mL min-1, and a pH of 7.75 of the carrier (0.1 mol L-1 phosphate buffer). The calibration curve exhibited linearity in the concentration range 10-160 mg L-1, with a detection limit (as 3s value) of 1.7mg L-1, and a relative standard deviation 3.3% (c=20 mg L-1, n=10). This biosensor was used for the determination of monosodium glutamate in food seasonings, and the values obtained were similar to those obtained with spectrophotometry. The biosensor exhibited extraordinary stability when left on the FI system at a flow rate of 0.1 mL min-1 at room temperature retaining 50% of the original response towards glutamate even after 65 days. Stored in the working buffer for more than 60 days, the same biosensor showed extended linear range, 20-710 mg L-1. This 'aged' (stored) biosensor was used to determine monosodium glutamate in food seasonings and gave similar result to those obtained with a freshly prepared biosensor.
(South African Journal of Chemistry: 2003 56: 54-59
A new amperometric ß-ODAP biosensor
No full textIntroduction The Lathyrus/lathyrism challenge is broad-based by its nature and requires multi-disciplinary efforts of specialists in the field of epidemiology, neurology, biochemistry, chemistry, nutrition, and agronomy. The role of chemists is in systematic determination of minor natural products in L. sativus seeds so that the sole responsibility of ß-ODAP for neurolathyrism is ascertaine
Optimization of a new chemiluminescence sensor based on peroxyoxalate chemiluminescence
No full textThe optimization of the experimental conditions for using new single-shot sensors based on chemiluminescence (CL) with two oxalate esters is presented. The new sensors are suitable for the determination of hydrogen peroxide in different kinds of samples. Each sensor contains an oxalic acid ester, a fluorescer, and a polymer. Bis (2,4-dinitrophenyl) oxalate (DNPO) and bis (2, 4, 6-trichlorophenyl) oxalate (TCPO) are used as esters in chemiluminescent reagents. The fluorescer and the polymer in both systems was 9, 10-diphenylanthracene and cellulose acetate. The polymeric membrane on a transparent glass support contained reactants and was placed over a photocell as detector, the sample was directly applied onto the membrane. The composition of the membrane was optimized. The sensors will be tested on samples of commercially available washing powders
Simple and Effective Procedure for Immobilization of Oxidases onto MnO2-bulk-modified, Screen-printed Carbon Electrodes
No full textNafion(R) film entrapment of oxidases onto the surface of MnO2-(5%, m:m) bulk-modified, screen-printed carbon electrodes was studied taking the inexpensive glucose oxidase as a model enzyme. The Nafion(R)-enzyme film was formed by drop-coating the suspension onto the surface of the electrode. Comparisons weremadeamong biosensors developed by using as-received, neutralized, and diluted (to 1% in methanol, ethanol or phosphate buffer) Nafion(R) in a flow injection (FI) mode. The amperometric response to injections of standard glucose solution was the highest for biosensors produced using neutralized Nafion(R). The effect of enzyme load per electrode (10-1190 mg) was investigated and 50 mg enzyme in the film per electrode was found to produce very good sensitivity as well as to be economical. Good reproducibility was achieved for three different biosensors (RSD of the means = 5.7%). The operational parameters for the glucose biosensor produced with this immobilization procedure were assessed and figures of merit obtained at the selected parameters. It has been observed that the effect of Nafion(R) to repel interfering ions like ascorbate and urate was lacking in this system. A preliminary investigation incorporating a hydrogen peroxide permselective membrane layer prior to enzyme immobilization gave promising result with polyurethane.
South African Journal of Chemistry Vol.57 2004: 1-
