On-chip liquid phase microextraction integrated with a COF-modified electrochemical sensor for trace determination of morphine in urine.

This study presents a novel design of a millifluidic chip that integrates liquid phase microextraction with analyte detection through an electrochemical sensor. Upon incorporating the sample solution that includes the model analyte, morphine, into the donor part of the millifluidic chip, passive diffusion occurs as it traverses the supported liquid membrane, influenced by the pH gradient. The innovative sensor utilizes a platinum electrode (Pt) that is modified with a synthesized covalent organic framework (COF) based on 4,4'-methylenedianiline and 4,4',4''-((1,3,5-triazine-2,4,6-triyl) tris(oxy)) tribenzaldehyde (MDA-Trz-COF, referred to as MDA-Trz-COF/Pt. Following the extraction duration in the acceptor part, a differential pulse voltammetry determination of morphine was conducted. The parameters influencing the electrochemical-liquid phase microextraction (LPME) chip were refined through one-variable-at-a-time and central composite design methodologies. In ideal circumstances, the maximum current responses were observed during the oxidation of morphine on the MDA-Trz-COF/Pt electrode versus various concentrations of morphine within two distinct linear ranges of 5.0-120.0 and 120.0-700.0 pmol L-1, with a limit of detection of 1.5 pmol L-1 and a limit of quantification of 5.0 pmol L-1, respectively. The efficacy of the proposed method for the preconcentration and quantification of morphine in urine samples was thoroughly examined.