In-tube electrochemically controlled solid phase microextraction of amitriptyline, imipramine and chlorpromazine from human plasma by using an indole-thiophene copolymer nanocomposite

The paper introduces a novel poly(indole-co-thiophene) composite for on-line electrochemically controlled solid-phase microextraction (SPME) of the antidepressant drugs amitriptyline (AMI), imipramine (IMI), and chlorpromazine (CPZ). The poly(In-co-Th) coating was prepared by electropolymerization and deposition on the internal surface of a stainless steel tube. An online SPME-HPLC system is obtained by replacing the sample loop of a six-port injection valve by the modified tube. The morphology and surface properties of the composite coating were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Central composite design and response surface methodology were used to optimize the voltage applied, adsorption and desorption times, the pH value of the sample solution, sample flow rate and acid concentration of the desorption eluent. Following elution with 10 mM HNO3 in methanol, the drugs were quantified by HPLC with UV detection at 210 nm. The method displays a linear response in the 35 to 1000 ng mL(-1) drug concentration range in case of spiked water samples. In case of plasma samples, the range extends from 80 to 1000 ng mL(-1). Other figures of merit include (a) limits of detection of < 40 ng mL(-1), (b) recoveries from spiked samples within the 24-64% range, (c) intra- and inter-day precisions (RSDs; for n = 3) of < 3.5% (at a concentration of 200 ng mL(-1)), and (d), relative recoveries within the range of 82.5-120%. This in-tube method was successfully applied to the analysis of the 3 drugs in human plasma samples.