Polyaniline‐silica doped with oxalic acid as a novel extractor phase in thin film solid‐phase microextraction for determination of hormones in urine

Abstract

In this study, different polyanilines were synthesized and evaluated for the determination of three hormones, including 17‐β‐estradiol, 17‐α‐ethinylestradiol, and estrone, in urine using a novel methodology based on thin film solid‐phase microextraction technique, employing the sampling well plate system. The extractor phases, designated as polyaniline doped with hydrochloric acid, polyaniline doped with oxalic acid, polyaniline‐silica doped with hydrochloric acid, and polyaniline‐silica doped with oxalic acid, were characterized by electrical conductivity measurements, scanning electron microscopy, and Fourier transform infrared spectroscopy. The optimized extraction conditions were composed of 1.5 mL of urine and pH adjusted to 10, with no need to dilute sample and the desorption step, 300 μL of acetonitrile was used. The calibration curves were performed in the sample matrix, with detection and quantification limits ranged from 0.30 to 3.03 μg L−1 and from 1.0 to 10.0 μg L−1, respectively, with r ≥ 0.9969. The relative recoveries ranged from 71% to 115%, and intraday precision showed values ≤12% and interday ≤20%. The applicability of the method was successfully evaluated, and six urine samples from female volunteers were analyzed. The analytes were not detected or were below the limits of quantification in these samples.