In liquid chromatography, the pump is responsible for maintaining a constant flow of the mobile phase… and when something goes wrong, the chromatogram shows it.
Whether it's a small noise in the baseline, a pressure that rises for no apparent reason, or a flow that becomes unstable, many times the origin is there: in the pump.
High pressure vs. low pressure: it's not all about strength
- High-pressure gradient system
It mixes the solvents after the pump. It is accurate and fast, although it may deliver a slightly lower flow than programmed due to solvent contraction. - Low-pressure gradient system
Mix the solvents before the pump. This is more flexible, but it introduces a delay in the arrival of the gradient to the column, something to consider in methods with rapid ramps.
What signs tell you that something is wrong?
- Repetitive noise on the baseline
- Pressure spikes with no apparent cause
- Poorly reproducible gradients
- Visible leaks or salt buildup near connections
- Loss of priming or difficulty starting the flow
Most of these symptoms point to problems with check valves, pistons, seals, or trapped air bubbles.
Maintenance that makes the difference
A well-maintained pump is an invisible pump. Replacing seals regularly, purging with deionized water at the end of the day (especially if you use phases with salts), and being attentive to the first signs of wear are what make the difference between a smooth routine and a day full of surprises.
