Abstract
Amperometric bienzyme electrodes based on coupled l-glutamate oxidase (GlO x ) and horseradish peroxidase (HRP) were constructed for the direct monitoring of l-glutamate in a flow injection (FI)-system. The bienzyme electrodes were constructed by coating solid graphite rods with a premixed solution containing GlO x and HRP crosslinked with a redox polymer formed of poly(1-vinylimidazole) complexed with (osmium (4-4′-dimethylbpy) 2Cl) II/III. Poly(ethylene glycol) diglycidyl ether (PEGDGE) was used as the crosslinker and the modified electrodes were inserted as the working electrode in a conventional three electrode flow through amperometric cell operated at −0.05 V versus Ag∣AgCl (0.1 M KCl). The bienzyme electrode was optimized with regard to wire composition, Os-loading of the wires, enzyme ratios, coating procedure, flow rate, effect of poly(ethyleneimine) addition, etc. The optimized electrodes were characterized by a sensitivity of 88.36±0.14 μA mM −1 cm −2, a detection limit of 0.3 μM (calculated as three times the signal-to-noise ratio), a response time of less than 10 s and responded linearly between 0.3 and 250 μM (linear regression coefficient=0.999) with an operational stability of only 3% sensitivity loss during 8 h of continuous FI operation at a sample throughput of 30 injections h −1.
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