Chromatography Forum

To all,

This question is sort of a "next step" to a problem we were seeing in our voa department on three 5973s and internal standard loss with increased analyte concentration. It was discovered that the analyzer and chamber walls are COVERED in diffusion pump oil. I can only theorize the reason was rough pump maintenance without prior chamber venting. We have a couple options, replace analyzer and electronics at a cost estimated at 10,000 each, or taking apart the analyzer and hand rinsing everything with petroleum ether, recommended by a pro. He said a task like this would be a major undertaking, and would require a couple gallons of pet ether to do a proper cleaning.

My question is, has anyone ever done this, and are there documents available that show the best procedure for dismantling a 5973 to its bones and properly put it back together?

Yes, i did it (disassemble > washing with n-hexane, acetone > drying under room temp > reassemble > pumping down > 3-4 day > testing/tuning). It's not so difficult or tricky, but you must be very careful and keep all parts clean and dust free (i used compressed air) at reassemble step. Also don't forget lubricate gaskets and replace diffusion pump oil. I'm not used any manuals/guides.

Dichloromethane cleans Santovac 5 diff pump fluid off of surfaces very well indeed.
You will need proper safety equipment, i.e., heavy nitrile gloves and respirator and be extra careful not to get DCM on your skin.

More likely cause of diff pump contamination is failure or reduced flow of your diff pump cooling water. Check your chilled water supply and any inline filters.

'Crabs

If you could find a solvent that was safe for the entire analyzer, a do-it-yourself version of vapor degreasing might be an option.

Isopropyl alcohol is the safest solvent for most of the analyzer. Forget about your electron multiplier - that is gonna have to be replaced (around 1200$ ea last I checked). When it comes to the quadrapole and HED, be really gentle and take your time - full submersion with gentle agitation is the way to go. Its gonna take several rinses to get it all off. The source can be cleaned in the usual manner, with the exterior parts being wiped down with lint free wipes soaked in IPA. The inside of the chamber can just be wiped down with lint free wipes soaked in IPA, and the electronics can be cleaned with a q-tip. Don't use DCM (or any chlorinated solvent) on any parts that have plastic or coatings such as wires, the PCB, etc. Make sure you give the whole thing a very thorough blasting with a can of duster, particularly the HED and quad. Compressed air can work too, but be aware that air compressors can sometimes have a lot of moisture in them, which will put you back to square one if it gets on the HED or Quad. Let everything dry for a full day, when you pump down, don't turn on your source or quad heaters for at least a day, and pray that you don't get all types of weird noise on your tune.

I agree with mdevay - chlorinated solvents are very bad choice. In my case, i had only chamber and quad radiator (a little) contaminated by diffusion pump oil (i used n-hexane then acetone then n-hexane again, both solvents - hplc grade). I used cotton swabs and lint-free wipes wetted with appropriate solvent for cleaning quad radiator. You can use n-hexane and IPA.

The cleaning steps above are the way to go, especially hexane/IPA. Is the inside completely covered or just droplets on the fins at the bottom and a little on the radiator?

As for the original problem with the internal standards, that is one that is very common when using purge and traps and there are as many theories as there are answers. I have posted on here some experiments I have done on this and what I found concerning internal standard responses versus standard concentrations, it should be easy to find if you search for my posts.

As for the diff pump cooling, the Agilent ones use air cooling instead of water cooling so you have to watch that the fan on the front doesn't get clogged with dust, and keep the fins on the outside of the pump clean also. There will always be some oil on the fins at the bottom of the analyzer chamber but it shouldn't be anywhere else unless you have a bad problem somewhere, and venting at the rough pump instead of the vent valve on the analyzer will certainly do it.