HPLC Pump selection for RI Detector

[h.piatkowski@comalc.com]

Here is what I found.. it looks like more than 2% if I am looking at it correctly.. I will try to post the link..


Hope it works..

Thanks
- Hubert

[JesseG]

The scale on the Y axis needs to be changed to bar (instead of detector units). Does this show the RI baseline bumps you spoke of?

[h.piatkowski@comalc.com]

OK, here we go again.. I think this is what you are looking for,.....



To me it looks like we are less than 1 % if I am looking at this correctly.. that would be good.....

The red line is injection point and the driop in pressure before that is unknown to me.. looks kind of weird though.. I would think the pressure should stay the same no matter if sample is injected or not..

Thanks again for helping me out here..

- Hubert

[JesseG]

The pressure drop just before injection is what we get also. The large spike downward usually indicates that our system is clogged. I would change the Inlet frit, and the frit or whole active inlet valve as well as take apart and clean the pump head.

Because you are running acid you may have some built up rust. The stator face could also have a small clog. When was the machine last PMed? You may need to do this in either 3,6 or 12 month intervals.

It may also help to flush the entire system with a solvent that would clean out and residue from samples or contamination from mobile phase.

[h.piatkowski@comalc.com]

The large spike downward usually indicates that our system is clogged. I would change the Inlet frit, and the frit or whole active inlet valve as well as take apart and clean the pump head.

Because you are running acid you may have some built up rust. The stator face could also have a small clog. When was the machine last PMed? You may need to do this in either 3,6 or 12 month intervals.

It may also help to flush the entire system with a solvent that would clean out and residue from samples or contamination from mobile phase.

The machine is on a yearly PM from Agilent, with our last visit about 6 mnths ago or so.. I will check the frits and make sure all is good in there.

If I wanted to flush the system, what's a good solvent to use? I believe in the past we have used IPA but not too sure. Also, when I do this I disconnect before the column right..

Thanks for the help
- Hubert

[JesseG]

Its best to have the column disconnected for flushing.
As I said, we use chloroform, and we use a 10% nitric acid solution to flush our system. This seems to take care of any, rust, particulate and built-up sample residue (we run polymer GPC). For your system probably flush with water than the nitric than water again.

[h.piatkowski@comalc.com]

Hi Again,

So basically, just water flush for 10 min or so, flush with 10% nitric acid for 10 min and water again.. right? Or should I make the times longer ?

Does it make sense to flush the detector as well or can I damage it somehow?

Thanks
- Hubert

[JesseG]

Since your mobile phase is aqueous, I would flush with HPLC grade water for 15 to 30 minutes (you'll need to get out any residual acid). Flush with nitric for 1 to 2 hours then back to water for at least 2 hours. You'll want long flushes to get out any residual junk or acid.
You shoukld flush the detector also, you can get buid-up on the detector cell.

[h.piatkowski@comalc.com]

Thanks a million to everyone that helped me out. I'm sure I will have more questions in the future..

Thanks again everyone !!!

- Hubert Piatkowski