Extraction and determination of papaverin in pericarpium papaveris using aqueous two-phase system of poly(ethylene glycol)-(NH4)2SO4 coupled with high-performance liquid chromatography

Based on aqueous two-phase system (ATPS) of poly(ethylene glycol) (PEG)–(NH₄)₂SO₄, a simple pretreatment approach was developed for the extraction and determination of papaverin in pericarpium papaveris. The influence factors on phase behavior of the ATPS and partition behavior of papaverin was investigated, and partition mechanism based on the hydrophobic interaction between PEG and analyte molecules was proposed. Under the optimal conditions, the extraction efficiencies for papaverin were 93–96%, and the recoveries of the added standard were 97–106% with relative standard deviations of 1.8–2.5%. Combined with a high-performance liquid chromatography (HPLC) method, this extraction technique has been successfully applied to the determination of papaverin in pericarpium papaveris with the detection limit of 2 ng mL⁻¹ and the linear range of 0.10–10 μg mL⁻¹. Compared with the conventional liquid–liquid extraction or solid-phase extraction, this method was more environmentally benign, more cost effective and much simpler due to the direct injection of the upper phase into HPLC system.