The determination of glucose, hypoxanthine and uric acid with use of bi-enzyme amperometric electrodes

An inexpensive and easy to construct miniaturized biosensor is described for the determination of uric acid in biological fluids. The amperometric biosensor was prepared by using a carbon paste electrode prepared with uricase from Arthrobacter globiforms and tetracyanoquinodimethane as electron transfer mediator. When incorporated into a flow-injection system it was enabled to perform 50 measurements/h of uric acid in the analytical range of 1 -100 mmol dm À3 with a relative standard deviation of 0.20% (n ¼ 14). The system was applied to human serum samples analysis providing good data correlation with those obtained by the reference spectrophotometric method. A linear relationship AM (mmol dm À3 ) ¼ 1.02 (AE 0.05) SP (mmol dm À3 ) À 0.12 (AE 0.13) was obtained evidencing the absence of significant error. The constructed biosensor was successfully used for at least four months (250 assays) with only a 13% of decrease in the enzymatic activity.

Section: Introductionmentioning

confidence: 99%

An Inexpensive Biosensor for Uric Acid Determination in Human Serum by Flow-Injection Analysis

Dutra

Moreira²,

Oliveira³

et al. 2004

“…Generally, direct electron transfer between common electrode materials and immobilized HRP is a slow process while electron transfer via a mediator presented in solution, called as the secondgeneration biosensors [13,14], is more effective in the bioelectrocatalytic reduction of peroxides at HRP-based sensors with detection limit as low as 10 ¹7 -10 ¹8 mol L ¹1 . Many mediators, such as ferrocene and its derivative [15,16], hexacyanoferrate [17][18][19][20], o-phenylenediimine [21,22], meldola blue [23], methylene green [24], have been used to enhance electron transfer rate between immobilized HRP and the electrode.…”

Section: Introductionmentioning

confidence: 99%

A Reagentless Hydrogen Peroxide Biosensor Based on the Coimmobilization of Thionine and Horseradish Peroxidase by Their Cross-Linking with Glutaraldehyde on Glassy Carbon Electrode

Zhou

Chen

1998

A novel reagentless H 2 O 2 sensor, based on the coimmobilization of horseradish peroxidase (HRP) and the redox dye thionine by their cross-linking with glutaraldehyde on the surface of a glassy carbon electrode, was fabricated. This resulting modified electrode exhibited good electrochemical activity in aqueous solution, and the electron transfer rate constant between the derivative thionine and glassy carbon electrode was about 0.097 s ¹1 (calculated from Laviron method). The apparent surface coverage of thionine was about 8.54 × 10 ¹12 mol cm ¹2 . It was found that thionine could mediate the electron transfer of HRP with the electrode substrate. Performance and characteristics of the biosensor were evaluated with respect to response time, detection limit, applied potential, pH, and temperature. The results inidcate that this biosensor is of high sensitivity to hydrogen peroxide with a low detection limit down to 1.0 × 10 ¹7 mol L ¹1 . Moreover, dopamine, ascorbic acid, and uric acid did not interfere with the determination of H 2 O 2 . Meanwhile, this enzyme electrode also showed good stability and reproducibility for long-term use.

“…Another approach is the monitoring of the formation of uric acid by its oxidation at t 0 . 4 V (vs. Ag/AgCl) at a carbon paste electrode 117,181, Other authors [12,16] used the H,02 to oxidize ferrocyanide in a reaction catalyzed by peroxidase (E.C. 1.11.1.7).…”

Section: Introductionmentioning

confidence: 99%

Membraneless immobilization of xanthine oxidase on organic conducting salt/silicone oil electrodes

Korell¹,

Spichiger²

1993

Xanthine oxidase (XOD, E.C. 1.2.3.2) has been immobilized on amperometric electrodes made from the orsanic conducting salt tetrathiafulvalene-p-tetracyanoquinodimethane (TTF-TCNQ) and silicone oil. Xanthine oxidase was immobilized by various techniques; immobilization by means of hydrophobic interaction was found to yield optimum analytical performance. Except for buffer, no coreactants are required for sensor operation. The response of the XOD electrode to its substrate hypoxanthine can be described by the enzyme-kinetic Michaelis-Menten formalism with excellent correlation (in most cases, 1 " > 0.995). Steady-state currents are usually measured within 10 seconds. Apparent K,, (typically 3 to 10 p M ) and saturation current values (0.2 to 3.7 PA, measured with new electrodes) strongly depend on the preparation procedure chosen as did the useful lifetime of the XOD sensors which was up to several weeks at room temperature. The described immobilization methodologies circumvent diffusion problems associated with well-established biosensor preparation techniques (e.g. , physical entrapment in gel or between dialysis membranes) and thus yield biosensors of superior analytical performance.