A Novel Adsorptive Square Wave Voltammetric Method for Pico Molar Monitoring of Lorazepam at Gold Ultra Microelectrode in a Flow Injection System by Application of Fast Fourier Transform Analysis

Abstract

This paper describes development of a new analysis system for determination of lorazepam by a novel square wave voltammetry method to perform a very sensitive method. The method used for determination of lorazepam involves measuring the changes in admittance voltammogram of a gold ultramicroelectrode (in 0.05 M H₃PO₄ solution) caused by adsorption of the lorazepam on the electrode surface. Variation of admittance in the detection process is created by inhibition of oxidation reaction of the electrode surface, by adsorbed lorazepam. Furthermore, signal-to-noise ratio is significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction, and two-dimensional integration of the electrode response over a selected potential range and time window. Also in this work, some parameters such as SW frequency, eluent pH, and accumulation time were optimized. Calibration plots are given for solutions containing 10⁻⁶–10⁻¹¹ M of lorazepam. The detection limit is calculated to be 6.0 × 10⁻¹² M (∼ 2 pg/ml). The relative standard deviation at concentration 3.0 × 10⁻⁸ M is 6.1% for 5 reported measurements.

Keywords:

• Fast Fourier transformation
• Flow-injection
• Gold ultramicroelectrode
• Lorazepam
• Square wave voltammetry

This was supported by the research council of University of Tehran.