Efficient design for in situ determination of amlodipine in whole blood samples using fast Fourier transform stripping square wave voltammetry after preconcentration by electromembrane extraction

Abstract

In this work, amlodipine (AML) was determined in whole blood samples based on coupling of fast Fourier transform stripping square wave voltammetry (FFTSWV) and electromembrane extraction (EME). The supported liquid membrane (SLM) comprised 50 μL 2-nitrophenyl octyl ether (NPOE) soaked into the pores of a hollow fiber. In order to electrochemically determine the amount of analyte, three microelectrodes were placed at a pipette tip and inserted in the upper end of a hollow fiber. The basic factors affecting extraction recovery such as extraction time, electrical potential and pH of donor phases were optimized using central composite design and response surface methodology. By applying a 250 V dc potential for 21 minutes, the charged target analytes were extracted from a phosphate buffer of pH 5.5 through the pores of the SLM and then into the lumen of the hollow fiber (phosphate buffer pH 4). The calibration curve was assessed under the optimized conditions and the method displayed two wide linear ranges, 0.1–10 and 10–1000 ng mL⁻¹, with determination coefficients of 0.99 and 0.98, respectively, in whole blood samples. Preconcentration factor of 61 was acquired after micro-extraction process. The intra- and inter-day precisions were calculated and RSD% (n = 3) were 4.5% and 7.5%, respectively. Limits of detection and quantification were found to be 0.05 ng mL⁻¹ and 0.1 ng mL⁻¹, respectively.