DIFFERENTIAL-PULSE VOLTAMMETRIC DETERMINATION OF RNA AT THE PICOMOLE LEVEL IN THE PRESENCE OF DNA AND NUCLEIC-ACID

A procedure for determination of nanogram quantities of RNA in the pre scence of an excess of DNA and monomeric nucleic acid constituents is presented. The procedure is based on immobilization of RNA by incubati on of a hanging mercury drop electrode in a 5-mu L sample followed by washing and transfer of the nucleic acid-modified electrode in a volta mmetric cell containing blank background electrolyte. The differential pulse voltammetric response of RNA differs from that of DNA. This mak es it possible to determine traces (less than 1%) of RNA in DNA sample s. Low molecular mass substances such as bases, nucleosides, and nucle otides do not interfere with the RNA determination as they do not adso rb at the electrode surface or are removed during the washing step. Th e limit of detection is below 100 pg of RNA. The new method ts more se nsitive and selective than currently applied techniques and overcomes the drawback of absorption spectroscopy arising from a strong interfer ence due to nucleic acid bases and other UV-absorbing substances.