Trace-Level Determination of ACE Inhibitors in Wastewater of Al-Kharj Governorate Using Solid-Phase Extraction–Capillary Electrophoresis Aided by Field Amplified Sample Stacking: A Sustainable Analytical Approach

Particularly in regions experiencing rapid industrial and healthcare development, the presence of pharmaceutical residues in wastewater is becoming an increasingly pressing environmental concern. In this study, an analytical method was developed to quantify lisinopril (LIS), ramipril (RAM), and enalapril (ENA) in wastewater while being both sensitive and inexpensive. To improve the precision and accuracy of the measurements, propranolol (PRO) was used as an internal standard. To achieve dual preconcentration and enhanced sensitivity, the method integrates filed amplified sample stacking (FASS) with solid-phase extraction (SPE) before capillary electrophoresis (CE) in a synergistic way. Important experimental factors such the composition of the background electrolyte (BGE), pH, injection settings, stacking efficiency, and selection of the SPE sorbent were meticulously calibrated. Under ideal circumstances, the SPE-CE-FASS method demonstrated remarkable linearity within the concentration range of 10–1000 ng L−1 (R2 > 0.999), an outstanding level of accuracy (intra- and inter-day RSD < 6%), and satisfactory recovery percents (90–97%) in real wastewater samples. This method offers an eco-friendly and cost-effective alternative to liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) by reducing waste, using less solvent, and providing enough sensitivity for trace-level analysis. Hence, it is very suitable for the regular monitoring of angiotensin converting enzyme (ACE) inhibitors in complex wastewater matrices.