My boss mentioned a few things about the 3200-series Ultimate Binary pump. These semi-prep pumps are not exactly known for running a smooth flow anywhere near their max (~50mL) and the piston seals need to be fresh (run full pressure test to confirm leak tight) for best results. The mobile phase, solvent compressibility needs to be properly set for each channel too. System properly primed and kept within the sweet spot above 100 bars for best performance. Reverse phase is what they are made for. NP, more likely to have gas issues, depending on solvent choice of course. Maintain backpressure on pump's outlet valve and on the inlet side, use solvent pickup frits with ~ 40 u pores, not the 10u type used with analytical systems (or you will create vacuum in the solvent lines resulting in unstable baseline/pressure).
Note: We rarely use degassers with true Prep pumps (too much trouble and expense most of the time), but a small semi-prep system like you have can be used with one (many inline versions are available for flow up to 50 mL/min, even Waters sells one). He said that degassing semi-prep and prep solutions is easiest with ultra high purity helium being sparged into the tanks (vented) at ~ 2 psi. That is what they do for their NP prep systems flowing up to 1 L/min. The size of the mobile phase reservoirs makes sonication impractical.
