Heating and solvent evaporation are energy-intensive.
Mitigation: Heat integration (e.g., using condensate to pre-heat fresh solvent); switch to PLE/ASE which uses less solvent overall.
This is modern hot solid-liquid extraction under pressure. By heating the solvent above its normal boiling point (e.g., water at 200°C remains liquid under high pressure), ASE achieves rapid extraction.
Advantages: Extremely fast (15-30 minutes), low solvent use (10-50 mL), high automation. Mechanism: Elevated temperature increases solubility and diffusion, while pressure forces solvent into matrix pores. solid liquid extraction hot
While heat increases total extraction yield, it often reduces selectivity. More heat means more energy is available to overcome activation energies for undesired compounds (waxes, chlorophyll, tannins, lipids). Thus, hot extraction can produce a "dirtier" extract than cold maceration.
Heat can weaken the van der Waals forces, hydrogen bonds, and dipole-dipole interactions that bind solutes to the solid matrix (e.g., plant cellulose). This desorption step is often the rate-limiting factor; hot extraction helps liberate the solute more readily. Heating and solvent evaporation are energy-intensive
Typical ratios range from 1:5 to 1:20 (solid:solvent, w/v). More solvent increases yield but requires more energy for evaporation.
Hot extraction is not universally optimal. Major challenges include: By heating the solvent above its normal boiling point (e
The ideal solvent should have high affinity for the target solute, low toxicity, high volatility (for easy removal), and an appropriate boiling point. Common solvents: