TRACE MEASUREMENTS OF RNA BY POTENTIOMETRIC STRIPPING ANALYSIS AT CARBON-PASTE ELECTRODES

Remarkably low levels of ribonucleic acid (RNA) can be measured by coupling its adsorptive accumulation onto carbon paste electrodes with constant current potentiometric stripping analysis (PSA), The computerized PSA operation effectively addresses the high background response inherent to carbon surfaces, while the anodic pretreatment of the electrode greatly enhances the preconcentration efficiency. The detection limit for tRNA (10 pg, 4 x 10(-16) mol) is substantially lower than that reported recently (Palacek, E.; Fojta, M. Anal. Chem. 1994, 66, 1566) for analogous voltammetric measurements at mercury surfaces. Variables influencing the accumulation and stripping processes of RNA are explored and optimized. Results are reported for measurements of RNA in the presence of excess dsDNA, for PSA of synthetic polyribonucleotides, for hybridization of complementaty strands of synthetic polyribonucleotides, for enzymatic hydrolysis of RNA, and for now injection operation, Such solid electrode experiments obviate the need for mercury electrodes or a deoxygenation step and open the door for modern RNA detectors and probes.