This study is consisting of two sections. At first section a novel gold nanoparticle gold electrode was used to folic acid determination. In this part the selective oxidation of folic acid was investigated on the gold electrode. After sensor optimization, it was used to measure folic acid by differential pulse voltammetry. A good linear correlation was found between the peak current of folic acid and its concentration in the range of 1.0 × 10 – 8 to 1.0 × 10 – 6 mol L –1 with a detection limit of 7.50 × 10 – 9 mol L –1 . In second section, an electrochemical DNA biosensor was proposed as a screening device for the rapid analysis of folic acid using a pencil graphite electrode modified with salmon sperm ds-DNA. Solution pH, DNA concentration, time of DNA deposition and potential of deposition was optimized with RSM. After that the binding of folic acid to DNA immobilized on a pencil graphite electrode was measured through the variation of the electrochemical signal of adenine. Folic acid could be measured in the range of 0.1 – 10.0 µmol L –1 with a detection limit of 1.06 × 10 –8 mol L –1 . Key Words Folic acid; electrochemical; Sensor; Gold nanoparticle; DNA.
