Unique and earth-friendly RP-HPLC approach for quantification and degradation of metoprolol and enalapril maleate: a new approach to combination therapy

The synergistic effect of metoprolol (MET) and enalapril (ENA) enhances blood pressure control and reduces cardiovascular risks. Exploring their co-administration in a single formulation is crucial. This study aims to develop sustainable alternatives to toxic chemicals and reduce waste using an RP-HPLC approach to detect MET and ENA in bulk and pharmaceutical products. The RP-HPLC was configured in isocratic mode using an InertSustain C8 column (250 × 4.6 mm, 5 µm). The sample temperature was set at 5°C and the column oven at 40°C. The mobile phase consisted of a 50:50 mixture of a potassium phosphate buffer adjusted to pH 2.5 and ethanol. The method had a seven-minute runtime, a 20 µL injection volume, and a 1.0 mL/min flow rate. Linearity between MET and ENA was observed in the 3–60 µg/mL range, with R2 ≥ 0.999. ENA was detected and quantified at 0.29 µg/mL and 0.90 µg/mL, respectively. MET had a LOD of 0.33 µg/mL and a LOQ of 0.98 µg/mL. The method was accurate, with recovery studies showing 98–102%. The technique's stability was demonstrated by following International Council for Harmonization (ICH) criteria. Despite degradants, the method accurately detected and quantified MET and ENA, offering better qualitative and quantitative results.