Novel Strongly Basic Molecularly Imprinted Solid-Phase Extraction Sorbent for Simultaneous Determination of...

Catecholamines are important hormones and neuromediators in the human body. Simultaneous determination of both catecholamines and catecholamine metabolites in bodily fluids can help accurately diagnose dangerous health conditions like adrenal tumors. However, the biggest obstacle is the selective separation of these compounds from the biological matrix. In this work, we propose a novel, dual-recognition, non-covalent molecularly-imprinted polymer that utilizes strong anion exchange as the source of sorbent-analyte interaction. (4-Vinylbenzyl)trimethylammonium-homovanillyl alcohol anion salt and (4-vinylbenzyl)trimethylammonium-homoveratric acid anion salt served as template/functional monomer complexes for catecholamines and acidic metabolites, respectively. The sorbent was synthesized using precipitation polymerization and studied with batch adsorption experiments, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller surface area and pore size analysis. The polymer was loaded into cartridges and tested with acidified urine samples. The analytes are deprotonated and adsorbed via sorbent's tetraalkylammonium moiety in hydroxide form, which also neutralizes excess acid, removing the need for pH readjustment (which is often necessary for urine analysis). The imprinted sorbent can also be reused at least four times without performance deterioration. Norepinephrine, epinephrine, dopamine, normetanephrine, metanephrine, vanillylmandelic acid, and homovanillic acid were separated and analyzed in a single run using molecularly imprinted solid-phase extraction combined with liquid chromatography-tandem mass spectrometry (MISPE-LC-MS/MS), with recoveries ranging from 69% (epinephrine) to 97% (homovanillic acid). Method's limits of detection, limits of quantitation, linearity, repeatability, trueness, and intermediate precision were evaluated. Limits of quantitation ranged from 0.7 to 6.5 µg/L (for catecholamines and metanephrines) and from 0.12 to 0.2 mg/L (for acidic metabolites). Compared to commercially available weak-cation exchange and hydrophilic-lipophilic balance cartridges, the imprinted sorbent produced stronger catecholamine signals with minimal volume of urine (25 µL). This study successfully demonstrated molecularly imprinted solid-phase extraction workflow for simultaneous separation and quantitation of urinary catecholamines and their basic and acidic metabolites, proving its compatibility with bioanalysis.