A CAPILLARY CARTRIDGE WITH AN ONLINE DESALTING DEVICE THAT ALLOW FASTSAMPLING FOR CAPILLARY ISOELECTRIC-FOCUSING

The capillary isoelectric focusing (CIEF) cartridge uses a 4 cm long, 75 mu m i.d., 150 mu m o.d. capillary. The two ends of the capillary a re connected to two pieces of 3 mm long, 150 mu m i.d., 170 mu m o.d. dialysis hollow fibers. These pieces are inserted into electrolyte res ervoirs attached to the two ends of the capillary. The fibers isolate the sample solution inside the capillary from the electrolytes in the reservoirs but allow small ions to pass freely, so that the isoelectri c focusing process can take place normally inside the capillary. With this cartridge, samples can be injected conveniently and quickly from one end of the capillary. After the sample injection, the separation v oltage is turned on and the focusing process begins, When the cartridg e is combined with a real-time, on-line absorption imaging detector, t he analysis time of the instrument for a sample is only 4 min, includi ng sample injection. The analysis time can be further reduced to about 30 s by using a 1 cm long capillary as the separation column. To pres erve the fast speed of this CIEF instrument, a fast, on-line desalting and carrier ampholyte mixing device using a dialysis hollow fiber was also designed. Protein samples 1-10 mu L, in volume can be desalted a nd mixed with carrier ampholytes and injected into the separation colu mn in an on-line fashion in 2 min, The new CIEF-desalting device was a lso developed with multiple capillaries, which increases the sample th roughput of the CIEF method. A three capillary cartridge was construct ed and tested. Total analysis time for three samples in the three capi llaries is only 5 min.