Green gradient RP-HPLC with variable flow rate for simultaneous analysis of paracetamol and ascorbic acid in pharmaceuticals

Paracetamol and ascorbic acid are widely incorporated into combination pharmaceutical formulations for the symptomatic treatment of cold and influenza. The present study reports the development and validation of a green, stability-indicating RP-HPLC method for the simultaneous quantification of these active pharmaceutical ingredients in bulk drug materials, intravenous infusion preparations, and effervescent tablet formulations using a microscale sample preparation strategy. Method validation was conducted in accordance with the ICH Q2(R2) guideline. Separation was achieved on a C18 chromatographic column using gradient elution with 0.015 M potassium dihydrogen phosphate buffer (pH 3.0) and methanol as the mobile phase components. A variable flow program ranging from 1.0 to 1.2 mL/min was applied, and analytes were monitored at 245 nm using a diode array detector maintained at 25 ± 2 °C. The method showed excellent linearity within concentration ranges of 3.2–29.3 µg/mL for ascorbic acid and 5.5–48.5 µg/mL for paracetamol. Forced degradation studies demonstrated effective separation of both analytes from degradation products, confirming the stability-indicating nature of the method. Green analytical assessment using AES, AGREE, MoGAPI, BAGI, and RGB12 yielded scores of 78, 0.60, 74, 80, and 96.7%, respectively.