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Highly Selective Electrochemical Biosensor for the Determination of Folic Acid Based on DNA Modified-Pencil Graphite Electrode Using RSM

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. At first, immobilization of the ds-DNA on pencil graphite electrode was optimized using response surface methodology. Solution pH, DNA concentration, time of DNA deposition and potential of deposition was optimized each at three levels. The optimum combinations for the reaction were pH 4.8, DNA concentration of 24 μg mL1, deposition time of304 s, and deposition potential of 0.60 V, by which the adenine signal was recorded as 3.04 μA. Secondly the binding of folic acid to DNA immobilized on a pencil graphite electrode was measured through thevariation of the electrochemical signal of adenine. Folic acid could be measure in the range of 0.110.0 μmol L1 with a detection limit of 1.06×108 μmol L1. The relative standard deviations for ten replicatedifferential pulse voltammetric measurements of 2.0 and 5.0 μmol L1 folic acid were 4.6% and 4.3%, respectively. The biosensor was successfully used to measure folic acid in different real samples.

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