STUDY OF A NEW SOLID CARBON-PASTE TYROSINASE-MODIFIED AMPEROMETRIC BIOSENSOR FOR THE DETERMINATION OF CATECHOLAMINES BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The performance of a tyrosinase-modified ''solid carbon paste'' electr ode (SCPE) as electrochemical detector has been studied in comparison with a glassy carbon electrode detector in high-performance liquid chr omatography for the simultaneous determination of dopamine, 3,4-dihydr oxyphenylacetic acid, norepinephrine and homovanillic acid. The influe nce of pH, flow-rate and amount of organic solvent in the mobile phase on the biosensor response was investigated. The stability and selecti vity of the detector were significantly affected by the mobile phase p H. No effect of 2% isopropanol in the mobile phase was observed. The b iosensor response was fast, reproducible, highly sensitive and linear over the concentration range 0.09 mu M(-1) mM (detection limit of ca. 290 pg of neurotransmitter injected).