Waters 2695 LC pump-lost prime

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

6 posts Page 1 of 1
Recently our Waters 2695 LC pump works irregularly:

When chemist edited a sequence, and prepared enough mobile phase, needle wash & seal wash solvents, he/she hoped to take the processed report in second morning(run code: run and report), but he/she found the sequence was stopped on some time and " lost prime" displayed on screen as alarming when returning the lab. We are very angry, because it cost our time to re-run the sequence. What causes this? :cry:

Any suggestions? Thank in advance!
The God had ever have three apples. Adam was tricked eating up one of them in Eden, and the second dropped from the tree and hit Issac Newton on his head, then what happened on the third one?Interestingly it was bit by Steve Jobs!

This is probably caused by your check valves (probably the right one).
Take a look at your mainenance procedures about how to change these.
Sonicating in hot water and afterwards acetone will help most of the times


First, these low volume degassers will typically have some issues with wide gradients, especially with methanol which is hard to degas. I had nightmares running wide methanol gradients in early method development on the 1100's. If possible, pre-mix as much as you can as outgassing can occur dropping an organic into aqueous even with passing through the degasser. The 2695's have a lot of issues with outgassing if they're allowed to stand very long, in my experience. Plus, the default prime flow rate is 7.5 mL/min x 3 min, I drop it to 5 x 5 for routine application to give it more residence time in the degasser. One way to ensure you don't have an air bubble at the start of the run is to pull with the dry prime function, close the valves, and (with the column disconnected) force some MP through the pumps. Often, you can disconnect the SUS-pipes (do they still call them that? - the tubing running into the check valves) and verify you have flow when running at 0.2 mL/min. It's a good way to rid yourself of stubborn bubbles. On the older Waters systems, if I took over from someone who let the system run dry I'd tranistion water to IPA and be done with it (methanol works too, it's easier to clean but not as effective). Could be a seal issue too, though I'd hold judgment on that until you're sure it's not just a stubborn bubble.


Lost prime is often due to check valves. This problem occurs with Methanol and the prime is very important before starting a sequence.

I think that zirconium balls stick into check valves with methanol. To fix it, you could perform Slammy1 procedure. Unscrew checkvalves and put it in isopropanol and sonicate it. Checkvlaves are Ok after that.


I was always thinking that acetonitrile was causing the checkvalves to fail.
Or buffer precipitation.

I am experiencing UNIQUE issue in Waters Alliance 2695 ver 2.04 . It works fine but during the injection the Needle Wash Pump do not asprirates or noting comes out from Yellow waste line. It happens in PURGE mode too. The valve opens and waste come out from CLEAR waste line but Needle Wash Pump doesnt activates. Not the Needle Wash Valve Green Tubing consumes washing bottle solution. We have checked both Needle Wash Pump and Needle Wash Valve in Waters 717 Autosampler both operates and functions well.
Plz input with guideline
6 posts Page 1 of 1

Who is online

In total there are 27 users online :: 0 registered, 0 hidden and 27 guests (based on users active over the past 5 minutes)
Most users ever online was 599 on Tue Sep 18, 2018 9:27 am

Users browsing this forum: No registered users and 27 guests

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry