Development of a green and rapid ethanol-based HPLC assay for aspirin tablets and feasibility evaluation of domestically produced bioethanol in Thailand as a sustainable mobile phase

Abstract Despite the growing trend of using ethanol as a greener alternative to hazardous solvents like methanol and acetonitrile in high-performance liquid chromatography (HPLC) analysis, no ethanol-based assay has been developed for aspirin tablets, nor has the potential of domestically produced bioethanol as a mobile phase been explored – until now. This study introduces a novel ethanol-based HPLC assay for aspirin and assesses the feasibility of using locally produced bioethanol. The optimized method, featuring a 40% (v/v) ethanol–water mobile phase adjusted to pH 3.6 with glacial acetic acid, with a 15-cm C18 column at 40°C and UV detection at 237 nm, successfully separated aspirin and its degradation product, salicylic acid, in 5 min. It demonstrated excellent linearity (0.1–0.6 mg·mL −1 , r ² = 0.9997), sensitivity (LOD = 0.01 mg·mL −1 , LOQ = 0.03 mg·mL −1 ), accuracy, and precision, with no interference from excipients. The method’s performance on commercial aspirin tablets aligned with official pharmacopoeial methods. In a case study using fuel-grade bioethanol (>99.5% purity) derived from sugarcane molasses or cassava from local manufacturers in Thailand, chromatographic and analytical results matched those obtained with imported ethanol, validating its effectiveness. This innovative approach not only reduces costs and dependence on imported solvents but also supports local bio-circular-green economies and promotes greener, more sustainable analytical practices.