waters E2695 normal backpressure without column

[thorn]

Hi, everyone

I am testing my HPLC machine's backpressure. Without any column under MeOH:H2O 30:70, flow rate: 1ml/min. The back pressure is about 1924 psi, delta pressure is 69psi. I think it's too high. I thought it is blogged. What's the normal backpressure it should be in the above conditions?

[Mritari]

Ours runs around 200 PSI. Perhaps your inline filter needs replacing? You could pull that and try cleaning it if you don't have a replacement(submerge in methanol and sonicate).

Are you using a union then plumbing through the detector, or is it going directly to waste where the column would be?

[mattmullaney]

Hi Thorn,

My experience is similar to Mritari's--also, are you using Waters 0.009 inch ID (0.23 mm ID) tubing? The backpressure will increase greatly as the tubing ID decreases.

The Delta P you note is probably also a bit...should be roughly less than 3 percent of the observed backpressure--and honestly most of the time more like less than 1 percent of the observed system backpressure...3% used to be Waters' recommendation as I recall.

Look for salt deposits at your plumbing connections throughout the system, I'd say, and best wishes that you get past the issue.

[thorn]

Mritari and mattmullaney,
Thank you for your replies.
I checked out the connections and filters in the whole system, and yes it turned out with salt deposits.I have replaced some parts and the system seems all right now.
The pressure downs to under 300 psi when flushing with Meoh at 3.0ml/min. 90 psi with MeOH at 1.0 ml/min
the delta pressure is stable blow 3% pressure too.