Chromatography Forum

I'm running on a Dionex ICS-2000. I recently needed to change out the guard column bc I was losing resolution. Once I did this the pressure was not as high as it should be (2000-2300psi). I know you can add backpressure restrictor coils to help with this but the ones that I currently have are not bringing pressure as high as I need. I've tried red and yellow gold coils. If anyone has any hints or ideas it would be great! thx...

Hi contestlabs,

Some questions:

• What was your pressure before and now after the guard change?
• What column set are you using?
• What is your flow rate?
• How many coils of red and/or yellow tubing do you have installed between the EG cartridge and the injection valve?
  • You can link them with a black coupler if needed to achieve higher pressures.

I'm using IonPac AG18 guard 4x50mm and Ion Pac AS18 column, @ 1.0mL/min using ECG KOH @ 32mM and suppressor at 80mA 4x250mm.
The pressure before I changed the guard was ~2100-2200 psi; however I was losing resolution on column and QCs failing; on inspection of the guard and column inlets i noticed the guard had lost headspace (column looked fine), then I replaced the guard.
Once I replaced the guard the pressure was around 1400psi with one red coil; I tried a gold coil but it was too high, trimmed gold coil a bit to see if it lowered, still not low enough...Currently I have 2 red coils together with a black coupler btwn the injection value and eluent out and the pressure is around 1700psi.
Perhaps I need to give the system more time?
Thx

There are two types of red coils and two types of yellow coils in the shipkit:

P/N 053764 is yellow tubing that gives 500 psi @ 0.5 mL/min
P/N 053765 is yellow tubing that gives 1000 psi @ 0.5 mL/min

P/N 053762 is red tubing that gives 500 psi @ 2.0 mL/min
P/N 053763 is red tubing that gives 1000 psi @ 2.0 mL/min

If you don't have the p/n, there should still be a label clipped to the tubing advising of the pressure @ x flow rate.

Based on your current pressure of 1400 psi, coupling the two red tubings together (053762 and 053763) should get you an additional ~750 psi @ 1 mL/min and bring your overall pressure to ~2150 psi.

Thanks John for your help!
I think I need to order another type of red coil and that should get the pressure where it needs to be...

Are you in Massachusetts? Perhaps we can collaborate. Also, I have loads of spare tubing and parts in my lab. I'd be happy to share what I can.