The document discusses various elution methods used in countercurrent chromatography, including elution-extrusion (EECCC), back-extrusion (BECCC), and intermittent countercurrent extraction (ICCE), highlighting their unique features and applications. It emphasizes the advantages of high-speed countercurrent chromatography, such as minimal sample preparation, high mass resolution, and reproducibility. The document also includes practical applications and examples of these methods in separating and purifying natural products.