Chromatography Forum

Dear friends,

Could you help me to troubleshoot this?

After downloading the method, pump rated at 0.7 ml/min, I noticed the pressure doesn't rise (0 - 2 psi), which may indicate the existence of a leak. When powered on, the run LED is amber (it should be green), but it flashes green while equilibrating the column but when it is time to perform a run, the run LED turns amber and the autosampler state says 'waiting for pump'.
The main window (PDA detector) status bar says: waiting for trigger. And nothing happens then.

Question: Despite the existence of a leak, the run LED should be flashing green, right?
Question: Why can't the run LED be green (without flashing) at the start-up, meaning it is in the ready state?

The manual says if the run LED is ambar, there may be a few motives:
1 - The LC pump is not communicating with the data system PC;
2 - the pump’s motor is stopped;
3 - the pistons are homing, or
4 - the pump is stabilizing (except during a run).

Any help provided will be very much appreciated.

Thanks.

What software?

Or maybe the pump needs primed, meant to pump liquids, not air.

grzesiek asked:
What software?

It's ChromQuest 4.2

Consumer Products Guy said:
Or maybe the pump needs primed, meant to pump liquids, not air.

I purged all the solvent lines already.

If I measure the amount of liquid sent to the waste bottle in time, would it be possible to check the existence of small leaks? Or some of it is retained inside the system for posterior discharge?

Thanks

dear friends...

If the pump heads contains air, How do I get that air out of the heads? Is it by purging all the solvents lines or only one is fine?

Thanks

Marcio, is it a thermo P4000 or 2000 series pump?

If so, the purge the pump heads with pure methanol. to prevent air entry to the pump via the mixing valve make sure the unused lines are filled (with methanol, and sitting in a methanol reservoir.

A quick way of evacuating air is to run the pump and (while running) loosen the connection on the top of each pump head. If there is air in the head it will escape and you retighten the connection when liquid starts to run out. (don't do this if you are using a buffered mobile phase, it can get messy)

Marcio, is it a thermo P4000 or 2000 series pump?
I don't know what series this pump belongs to.
If so, the purge the pump heads with pure methanol. to prevent air entry to the pump via the mixing valve make sure the unused lines are filled (with methanol, and sitting in a methanol reservoir.
Nince hint, thank you.

A quick way of evacuating air is to run the pump and (while running) loosen the connection on the top of each pump head. If there is air in the head it will escape and you retighten the connection when liquid starts to run out. (don't do this if you are using a buffered mobile phase, it can get messy)
I will try this as soon as possible. The solvents are water, methanol and acetonitrile, and still have one empty bottle.
What would be the problem if I do this with water only?

Here's an uploaded pic: click it!

Thank you.

Assuming that you have a column on line, 0-2 psi means that the pumps are not primed, still contain a lot of air or you have not closed the purge valve. Was this pump functional before you started working with it or was it sitting around and you are trying to make it work?

Assuming that you have a column on line, 0-2 psi means that the pumps are not primed, still contain a lot of air or you have not closed the purge valve. Was this pump functional before you started working with it or was it sitting around and you are trying to make it work?

The pump was working perfectly, the problem is, I added a new solvent to the system (mobile phase), acetonitrile, and I did not do as the manual says:

If the solvent line is dry, attach a syringe to the drain line, open the drain valve, make sure that the pump power is on, and then draw the syringe barrel back pulling solvent into the line.

So, it's very likely that the problem is that the pump heads are full of air, but if they really contain air, wouldnt purging one of the solvent lines solve the problem? let's say 9.999 ml/min of water for 10 min?

Thanks

Marcio:

To prime your pump, I would probably use a viscous solvent that is miscible with most other mobile phases (e.g. isopropanol). I've found this solvent to be good for priming pumps in the past.

To do this effectively, I would follow JGK's advice - following the flow path, and with the pump 'pumping', open up each fitting in the solvent flow path for enough time to see solvent leaking out of the fitting. Then re-tighten that fitting and open up the next fitting in the flow path. Once you've rid yourself of the air, you can switch to your mobile phase (with an intermediate of water if you're using a buffer).

dear friends...

loosing the fittings is such a great idea, but as you can see below, which fittings?

pump fittings

is it the wash assembly fittings? I am afraid the other fittings are made of metal, and loosing them may cause bigger problems. What do you think?

Should I do this while the drain valve is open(purging) or closed?

Thank you very much.

Marcio

Based on the schematic, I think that if you undo the line from the solvent proportioning valve, I believe you should have gravity flow though that line. If you don't, I would make sure you purge that valve first. I would then start with the line from the solvent proportioning valve into the primary pump check valve - make sure you have gravity flow out of that line. Then, with the pump on (you could probably have the purge valve closed, with the line out going to waste instead of to your autosampler/column, I would then sequentially open the connections in the path (inlet check valve, connection at primary pump to crossover tube, connection to secondary pump outlet check valve, then the connection to the outlet tube). You should only have to undo the connections at the pump enough to allow solvent to leak out (1/8 - 1/4 turn), and you should have some paper towels handy to catch leaks before they get out of hand. Once you have flow out of the secondary pump head, you should have flow through your purge valve (open and close it just to be sure you have flow to waste and flow to column, though).

The only other thing I can think of is that is you aren't building pressure and don't have flow out of your pump after doing this purge procedure, you may have a bad pump seal/plunger somewhere, or you might have an issue with the purge valve not seating when closed. If it's the latter, then you should be seeing mobile phase going to waste when the valve is closed, instead of going into your column.

I just loosened the crossover and outlet tubes fittings, and methanol leaked out for 5 seconds. It seems it did not work out.

or you might have an issue with the purge valve not seating when closed. If it's the latter, then you should be seeing mobile phase going to waste when the valve is closed, instead of going into your column.

You went right to the core of the matter. Problem's been solved. Pump's working again.

Thank you all.

So, can we assume the purge valve was the issue?