Improved method for continuous UV monitoring in high-speed counter-current chromatography

Continuous UV monitoring of the effluent in high-speed counter-current chromatography often encounters difficulty mainly due to the thermolabile nature of the mobile phase which tends to develop turbidity in the flow cell under a slight shift of the ambient temperature. This problem was effectively solved by inserting a fine PTFE tube (3 m x 0.46 mm I.D.) between the column outlet and the UV monitor and immersing a large portion of the tube into a waterbath heated at 30 degrees C. A similar tube was applied at the outlet of the UV monitor to create back pressure which suppressed gas bubble generation from the mobile phase. By the combined use of these devices, noiseless UV tracing was successfully demonstrated in two model experiments using thermolabile two-phase solvent systems: separation of flavonoids from the sea buckthorn ethanol extract with chloroform-methanol-water (4:3:2, v/v/v) and separation of bacitracin components with chloroform-ethanol-water (5:4:3, v/v/v).