Solid Phase Extraction trap. The trap column enables the rapid injection of relatively large sample volume into a nanoflow column. The injection flow rate depends on the dimensions of the trap. However, the ID of the trapping column should be in balance with the column ID. Use of -relatively- large ID traps results in unwanted band broadening in the final separation. The cause is the  low linear velocity [column flow x (IDcolumn/ IDtrap)2] of the mobile phase through the trap when switched in line with the column. According to the Van Deemter equation (Van Deemter, et. al., Chem. Eng. Sci. 5 (1956) 271), low mobile phase velocities result in a severe decrease in separation efficiency of the trap and hence, analytes will arrive in broader bands onto the analytical column.

300umID trap
50 umID column
100umID trap
50 umID column
delay 16 min
Trap ID Column ID Lin. velocity in Lin. Velocity in
(um) (um) column (cm/min) trap (cm/min)
300 100 6 0.670
300 75 6 0.375
100 75 6 4
100 50 6 1.5

Recommended trap ID/ column ID combinations
Column ID Trap ID trap flow rate (uL)
(um) (um) at 125 bar
200 200 40
100 100 10
75 100 10
50 100 10
25 50 3