Green HPLC Assay for Captopril Tablets with Integrated Laboratory Waste Management: A Paradigm of Sustainable Pharmaceutical Analysis Workflow Enabled by Agro-Waste-Derived Products

Background: Sustainable pharmaceutical analysis is essential for reducing environmental impacts from hazardous reagents, solvents, and residual active pharmaceutical ingredients (APIs). This study aimed to develop a green and practical workflow by integrating an eco-friendly analytical method with an effective post-analysis waste treatment approach, using captopril (CTP) as a case study. Methods: A high-performance liquid chromatographic (HPLC) method was developed for rapid, simultaneous quantification of CTP and its impurity, captopril disulfide (CDS), in tablet formulations. Bioethanol derived from sugarcane molasses was used as a greener alternative to conventional solvents. A 10 cm C18-column was employed to address ethanol-associated backpressure. The method was validated following ICH and United States Pharmacopeia (USP) guidelines. In parallel, a laboratory waste treatment protocol was developed using coconut shell-derived activated carbon, applied at ambient temperature (25 °C). Results: The optimized HPLC method, utilizing a mobile phase of ethanol, water, and phosphoric acid (35:65:0.05, v/v/v), operated at a flow rate of 1.5 mL/min and a column temperature of 40 °C, effectively resolved CTP and CDS within 2.5 min, allowing for high-throughput analysis and reduced energy consumption. It demonstrated excellent linearity, accuracy, precision, sensitivity, specificity, and robustness. Its performance was comparable to the USP reference method, with the added benefits of improved greenness and practicality. Treatment of the laboratory waste liquid by shaking with activated carbon at a 1:10 g/mL ratio removed over 99% of CTP within 5 min. Conclusion: This is the first ethanol-based HPLC assay for CTP, offering a greener alternative to existing methods. The integrated waste management strategy effectively reduces risk of API dissemination into the environment, addressing both ecological and public health concerns. Utilizing agro-waste in both analysis and waste treatment promotes resource efficiency and supports circular economy principles. This model contributes to sustainable pharmaceutical quality control in line with the Sustainable Development Goals.