Trace Detection of Diphenhydramine by Adsorption on a Microelectrode at Flow Injection System by Fast Fourier Transform Continuous Cyclic Voltammetry

A continuous cyclic voltammetric study of diphenhydramine at gold micro electrode was carried out. Some investigations were also done to find the effects of various parameters on the sensitivity of the proposed method. The experiments were performed under the following conditions: pH = 2, the scan rate = 40 V/ s (v), accumulation potential = 500 mV (E), and accumulation time = 0.2 s (t). The drug in phosphate buffer (pH = 2.0) is adsorbed at optimized condition on the surface of electrode, giving rise to change in the current of well-defined oxidation peak of gold in the flow injection system. The proposed detection method is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. Signal-to-noise ratio has significantly increased by application of discrete Fast Fourier Transform (FFT) method, background subtraction and twodimensional integration of the electrode response over a selected potential range and time window. The linear concentration range was from 4.0 × 10–7 to 1.0 × 10–11 mol dm–3 (r = 0.9987) with a limit of detection and quantitation 5 × 10–12 and 4 × 10–11 mol dm–3, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay diphenhydramine in tablets