Optimization of Thin-film Microextraction using a Polyelectrolyte Multilayer Sorbent Combined with HPLC-UV for Separation and Determination of Tricyclic Antidepressant Residues in Aqueous Samples

Thin-film polyelectrolyte multilayers (PEMs), namely poly(allylamine hydrochloride) (PAAH) and poly(styrene sulfonic acid) (PSS), were successfully prepared as a new extraction medium for drugs. Three kinds of tricyclic antidepressant drugs (TCAs), namely imipramine (IMI), amitriptyline (AMI), and chlorpromazine (CHLO) were selected as target model analytes. Thin-film microextraction (TFME) was performed by piercing 7 (approx. 8.4 mg) circular cellulose acetate-polyelectrolyte multilayers (CA-PEMs) (5 mm diameter) with a needle and directly dipping them into a sample solution which was agitated during the extraction process. The CA-PEMs were ultrasonicated for analyte desorption in 100 µL of organic solvent before analysis with high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Several important parameters such as type of desorption solvent, the effect of sample pH, salting-out effect, extraction time, desorption time, the volume of desorption solvent, and stirring speed were evaluated and optimized. Under optimized extraction conditions, the technique demonstrated good linearity in the concentration range of 10-1000 µg L^-1 for lake and river water samples, and 50-1000 µg L^-1 for urine samples. The detection limits were in the range of 3.7 - 40.5 µg L^-1. The percentage recoveries were generally in the range of 99 - 111.18 %, with an RSD of 2.6 - 4.7 % (n=3). The facile synthesis conditions also indicate that the proposed method has good applicability in terms of simplicity, effectiveness, selectivity and accuracy. Thus, this method proved to be a suitable alternative green method for analysis of TCAs in different matrices.