Sequence of supercritical CO2 extraction and subcritical H2O extraction for the separation of tobacco waste into lipophilic and hydrophilic fractions

[Display omitted] •Two-stage extraction process (SC-CO2 extraction followed by SWE) was conducted.•Enhanced extraction efficiency was observed.•Two-stage extraction enables separation of both free base and charged nicotine.•Two-stage extraction process completely avoids utilization of organic solvents.•With two-stage extraction process, completely exhausted material can be achieved. A tobacco solid waste was extracted by a sequence of supercritical CO2 (SC-CO2) extraction and subcritical water extraction (SWE). The tobacco waste lipophilic compounds (targeted fatty acids, free base nicotine and VOCs) were extracted using the series of the main operation parameters for the SC-CO2 extraction (pressure: 100–300bar, temperature: 40–80°C). The obtained SC-CO2 extracts were rich in nicotine (0.362–1.585%), neophytadiene (0.082–0.256%) and 4,8,13-duvatriene-1,3-diol (0.144–0.590%). Other VOCs and targeted fatty acids (palmitic, stearic, oleic, linoleic and linolenic) were also determined. Optimized condition for the SC-CO2 extraction of tobacco waste was found at 300bar and 61.22°C. The residues (after SC-CO2 extraction) were re-extracted with SWE under the solvent/solid ratio: 28mL/g, temperature: 150°C, time: 23min. SWE extracts (hydrophilic fractions) were characterized by high concentrations of nicotine (1.61–4.67%), nicotinamide (0.198–0.428%), nicotinic acid (0.118–0.239%), phenolic compounds: chlorogenic acid (0.458–0.740%), 3,4-dihydroxybenzoic acid (0.236–0.403%), neochlorogenic acid (0.240–0.534%), and rutin (0–1.025%). They contained total phenols in the amount 8.03–10.11% and exhibited DPPH antiradical scavenging activity in the range 77.89 to 93.35%. As the results of applied higher temperature 5-HMF (0.076–0.11%), furfural (0.510–0.740%) and 5-MF (0.0292–0.0453%) were also detected in SWE extracts. In some experiments, the obtained values of detected compounds were considerable higher than those obtained from the raw scrap (without SC-CO2 extraction pretreatment) implying that two-stage extraction process (SC-CO2 extraction followed by SWE) can enhance the extraction efficiency due to the elimination of fats during SC-CO2 extraction which enables better dissolution of the other compounds in subcritical H2O.