Separation and enrichment of nicotine from tobacco extract by emulsion liquid membrane

【Objective】 To optimize and construct a water-in-oil-in-water（W/O/W）type emulsion liquid membrane system for the effective separation and enrichment of high-concentration nicotine in tobacco extracts，providing reference for its development and utilization. 【Method】 Using nicotine as a template molecule，single-factor experiments were conducted to optimize the pH of the external aqueous phase，types and amounts of surfactants，types and amounts of membrane carriers，ratio of oil phase to internal aqueous phase，HCl concentration of internal aqueous phase，transfer time， and ratio of emulsion phase to external aqueous phase. Subsequently，a four-factor and five-level orthogonal test was performed on the pH of the external aqueous phase，the amount of membrane carrier D₂EHPA，the amount of surfactant T154，and HCl concentration of internal aqueous phase. The separation efficiency of the emulsion liquid membrane system for nicotine in tobacco extracts was evaluated using ultraviolet-visible spectroscopy and high-performance liquid chromatography（HPLC）to determine the optimal conditions of the emulsion liquid membrane system. 【Result】 In the orthogonal test，the influence of the 4 factors on the extraction rate of the emulsion liquid membrane system was ranked as follows：pH of external aqueous phase = amount of surfactant T154 > amount of membrane carrier D₂EHPA > HCl concentration of internal aqueous phase. By comparing the separation and enrichment efficiencies of the emulsion liquid membrane system optimized by single-factor and orthogonal tests，the optimal conditions obtained from the single-factor test were determined to be：3% T154 as surfactant，3% sec-octanol and 5% D₂EHPA as membrane carriers，0.5 mol/L HCl in the internal aqueous phase，pH 13 in the external aqueous phase，ratio of oil phase to internal aqueous phase of 10∶8，ratio of emulsion phase to external aqueous phase of 2∶25，and transfer time of 2.5 min. Under these conditions，the extraction rates for 0.05 mg/mL nicotine and nornicotine reached 85.07% and 91.42% respectively by emulsion liquid membrane system，and the separation and enrichment efficiency for nicotine components in tobacco extracts reached 74.80%，with the nicotine concentration in the separated sample being as 2.17 times as that of the original sample. 【Conclusion】 The optimized emulsion liquid membrane system can rapidly and effectively separate and enrich high-concentration nicotine from tobacco extracts，showing good potential for application.