A simple, rapid, and sensitive electroanalytical method for the direct quantification of folic acid was developed using square-wave voltammetry with a cathodically pretreated highly borondoped polycrystalline diamond electrode. The morphology and structure of this electrode were Downloaded by [University of Lethbridge] at 03:15 05 October 2015 2investigated by scanning electron microscopy and Raman spectroscopy. The electrochemical behavior of folic acid was studied by cyclic voltammetry and an irreversible oxidation peak was observed at +0.78 volt versus Ag/AgCl in Britton-Robinson buffer at pH 5. Using optimized square-wave voltammetry parameter values, the response of folic acid was linear from 0.1 to 167 micromolar with a limit of detection of 30 nanomolar with good repeatability. The influence of some interfering compounds was also evaluated. The method was successfully applied to the quantification of folic acid in pharmaceutical tablets. Considering the importance of the analyte upon human health, the boron-doped diamond electrode may be employed as an effective alternative electroanalytical approach.

Electrochemical methods have many inherent advantages such as simplicity, low cost and amenability to miniaturization. A new, sensitive and selective electrochemical method for the caffeine determination using boron doped diamond electrode was developed. It was found by cyclic voltammetry that caffeine provided highly reproducible and well-defi ned irreversible oxidation peak, at very positive potential of +1.55 V vs. Ag/AgCl electrode. The effect of pH and scan rate on the voltammetric response of caffeine oxidation were studied to select the optimum experimental conditions. Linear response of peak current on the concentration in the range from 4 × 10 -7 to 2.5 × 10 -5 mol L -1, good repeatability (RSD of 2.1 %) and the detection limit of 1.5 × 10 -7 mol L -1 without any chemical modifi cations and electrochemical surface pretreatment were observed by differential pulse voltammetry in 0.4 mol L -1 perchloric acid. The effect of possible interfering compounds appeared to be negligible which evidently proved very good selectivity. The proposed method was successfully applied for the caffeine determination in commercially available beverage samples, with results in a close statistical agreement to these declared by manufacturer.