Indirect determination of trace concentrations of amoxicillin in environmental samples using a low-cost, disposable additively manufactured sensor

Abstract

Amoxicillin (AMX) is the most consumed antibiotic from the β-lactam group due to its effectiveness against a broad spectrum of bacterial infections. Given the widespread application of AMX, there is a significant risk of environmental damage and global repercussions due to the hazardous nature of effluents generated by the pharmaceutical industry. Herein, we developed a simple, rapid, cost-effective, and sensitive procedure for the indirect electrochemical determination of AMX in water samples. The method utilizes differential pulse voltammetry (DPV) combined with a low-cost disposable working electrode fabricated through additive manufacturing (3D printing). Three sequential steps are proposed to enhance the detectability of AMX using the 3D-printed electrode: (i) chemical and electrochemical activation of the 3D-printed electrode surface in an alkaline medium (0.5 mol L⁻¹ NaOH); (ii) preconcentration of AMX through its adsorption onto the electrode surface; and (iii) oxidation of adsorbed AMX to its quinone-derived form, followed by its sensitive detection via electrochemical reduction and subsequent reoxidation. The mechanism of the electrochemical reactions was investigated and discussed using electrochemical techniques and supported by literature data. Under optimized DPV conditions, the activated 3D-printed electrode demonstrated excellent analytical performance, exhibiting a linear range from 0.1 to 5.0 µmol L⁻¹ and a limit of detection (LOD) of 0.01 µmol L⁻¹ (10 nmol L⁻¹). The possibility of using various detection strategies (AMX direct oxidation, reduction of AMX's oxidation product, and its re-oxidation) enhanced the selectivity of the voltammetric method, with no significant interference from multiple potential interferents (Pb²⁺, phenol, glucose, ascorbic acid, uric acid, ibuprofen, clavulanate, paracetamol, chloramphenicol, sulfanilamide, tetracycline, and ciprofloxacin). Using a simple sample preparation procedure (addition of or dilution in a supporting electrolyte), recovery values ranging from 82 to 106% for AMX in various water samples (river, lake, tap, and drinking water) were achieved.