Trace measurements of nucleic acids using flow injection amperometry

Flow injection analysis with amperometric detection is used for quantitating nucleic acids down to picogram level. The procedure relies on the oxidation of the bound guanine moiety at the untreated carbon paste detector, and does not require any prior derivatization or hydrolysis reactions. The response is evaluated with respect to flow rate, operating potential, type and concentration of the nucleic acid, and other variables. At a fixed potential of + 1.0 V (vs. Ag/AgCl) the detection limits for double-stranded DNA, single-stranded DNA and tRNA are 460, 540 and 750 pg, respectively. Good reproducibility (R.S.D.s of 1.9-2.9%) is observed for prolonged series (n = 30). The attractive behavior of the carbon paste detector holds great promise for monitoring nucleic acids in chromatographic effluents, and should facilitate new applications in molecular biology.