Plugged autosampler valve

[soccerdad007]

Hi all
I am having high pressure problems with a HP1100 system.

I have tracked it down to a plugged injector valve. When I connect the
pump outlet capillary to port 1 of the injector and connect the column-compartment inlet capillary to port 6 of the valve (as normal), I get a huge pressure increase (quickly greater than the limit of 400) as soon as I turn on the pump (even when as long as 0.1ml/min). If I bypass the autosampler injector valve, the pressure is v.v. low

Are there obvious things I should be doing. This system has worked well for years and I am not certain I can lay my hands on the manual

Thanks
Kevin

[Bruce Hamilton]

The manuals should be available on the Agilent site, along with a comprehensive series of maintenance training videos/files. If you haven't already, you need to confirm that the problem is the valve, and not the needle/seat assembly or a capillary line..

It's quite likely that you are going to dismantle the valve, so read and watch carefully before starting. All the necessary tools will have come with the instrument - try to find them, they make the task easier. It takes about 30 minutes to either repair blockages in the needle/seat or valve - but ensure you have spares before you start.

Before embarking on the disassembly, it is usually worth while to try and dissolve up any precipitated salts that may be the cause of the pressure. I've found one solution is to disconnect the lines between pump and injector, and pump and column, and put a longer, wider ID line in the pump side and a short line to waste on the column side.

Put as much as possible of the long line in a beaker of hot water and try to pump a highly aqueous ( 90+% ) mobile phase at the fastest rate your pressure will allow. If you suspect the blockage is caused by a sample component, you can try suitable solvents in place of an aqueous mobile phase.

If the salts dissolve, you'll get a dramatic pressure drop, if they don't, identify where you problem is using the manuals test regime, and start disassembly.

Don't try to reverse-pressurise any components - Murphy's law will demonstrate that other seals will also fail.

Please keep having fun,

Bruce Hamilton

[HPLCCONSULT]

If you are sure the plug is in the Rheodyne injection valve and not the injection seat or capillary (#1 spot for a plug), then simply remove the valve's stator plate and check for a plug in one of the plates threaded ports. While you are in there, inspect/clean/replace the valve rotor seal and clean the stator plate. Everything should be nice and clean inside with no corrosion or discoloration. Often you will find ground up plastic or buffer crystals inside the valve which often indicate a lack of maintenance and/or not flushing the system down each day.
BTW: The stator plate comes off easily with a 9/64" hex driver.

[Consumer Products Guy]

We've had this happen several times, and injection quality is perfect then the 1100 or 1050 injector valve is plugged up. Like others said, remove the three screws with 9/64" hex driver (we use a long one with a tee handle, and don't remove the individual lines either). We clean out any junk particles with methanol from a squeeze bottle, and replace the rotor seal. Be aware of the order of removal of the parts, they do have holes and pins to try to help you align correctly. The two tiny channels in the rotor seal is where your flow actually runs, faces out towards you. The 1050 and 1100 rotor seals are different, 1050 has four holes and 1100 has three.

[lmh]

but listen to HPLCCONSULT, do check that injection seat.

[Anthony_Ng]

The flow path from pump to column-compartment like this:

From pump outlet -> into port 1 -> out from port 2 -> through metering device -> loop -> needle -> needle seat -> into port 5 -> out from port 6 -> column-compartment

Before dismantle the valve (which I think is difficlut to assemble it ), I would make sure all capillaries, loop, needle and needle seat are not plug.

Hope that will help.

[HPLCCONSULT]

"Anthony_Ng": The valve is very easy to take apart and maintain. Agilent (HP) even provides some nice diagrams and instructions inside the operator's manual for the A/S. Regular maintenance requires that you remove the stator plate to inspect the valve interior, stator plate, isolation disk and valve rotor on a regular basis anyway so it something that every chromatographer should be familar with.