Figure 2.

Effect of flow rate and column to detector tubing dimensions on LC separation of a 3-component test mixture. (A) Different flow rates tested on the same column (Luna) with the same mobile phase (35/65 v/v acetonitrile/water + 0.1% TFA) for standard sample mixture of 13.3 mM thiourea, 6.7 mM 2,5-dihydroxybenzoic acid, and 16.7 mM phenylacetic acid. (B) Effect of changing inner diameter of column to detector tubing. 10.2 cm length fused silica capillaries with varying of inner diameters were installed on the same column and tested with the mobile phase as in (A). The standard concentration (std conc.) samples indicated above were used for 25, 40, and 50 μm i.d. capillaries, and half concentrated standard samples (1/2 std conc.) were used for 75 and 100 μm i.d. capillaries. Flow rates for all assays were 70 μL/min except for the 25 μm i.d. capillary, which operated at 60 μL/min and a resulting back pressure of 4800 psi, which was just below the 5000 psi pressure limit of the column.