Shorten the runtime of an isocratic run by increasing flow

[vivian.lwan968]

Did on an Agilent 1200 by doubling the flow rate (from 1 mL/min to 2 mL/min), the back pressure is around 300 bar (limit is 400 bar). The chromatogram looks fine.
My questions are:
How can I make sure there is no co-elution of my analyses after I "squeeze" my chromatogram?
Is it ok to push the back pressure to the upper limit? Any downside to the instrument?

[tom jupille]

With a reasonably "state of the art" column (3.5 micron or smaller particles), efficiency (the ratio of peak width to retention) does not change very much as flow is increased. If your peaks were well separated at 1 mL/min, they should be almost as well separated at 2 mL/min. I'm assuming small-molecule analytes here; for proteins, efficiency can drop significantly as flow increases.

On the downside, detector baseline noise usually gets worse at higher flow. The higher pressure *is* harder on seals and check valves, so you should probably do preventive maintenance more frequently. My biggest concern would be that column back pressure usually increases over time. If you are pushing the limit on a new column, that doesn't give you much slack.

[Consumer Products Guy]

Vivian - I assume that your motive is either to increase throughput (injections) per time, or to shorten the time when you would be able to report the results.

So if your analyte and any other stuff is well separated, try a shorter column with same packing and HPLC conditions, or bump up your organic percent a bit. If your organic is methanol, have you tried using ACN instead, delivers lower backpressure.