Liquid path switching: easily realize the conversion of collected liquid and waste liquid, improve method efficiency. Channel quantity: four channels, each channel can be used independently without affecting each other. Column disk universal: can use 1, 3, 6mL extraction columns and 47mm, 90mm extraction membranes. Flow control: Using a flow fine-tuning valve to accurately control the pumping flow rate of each channel improves the controllability and reproducibility of solid-phase extraction operations. Note: Anti corrosion materials: PTFE, stainless steel and other anti-corrosion materials are used in contact with solvents, which can withstand organic solvents such as dichloromethane