0.5uM stainless steel frit vanished!

[JDiaz]

Dear all,

Something quite strange has happened in my Dionex Ultimate 3000 HPLC.
The stainless steel filter frit that is placed in the outlet unit of the pump has vanished, only the plastic washer that holds it has remained!

My eluents are:

A: 10 mM KH2PO4 ph= 2.8
B: 500 mM KH2PO4 800 mM KCl ph= 2.8

Column: Whatman Partisil 10 SAX

Eluents are at ambient temperature

I guess it was a 0.5 uM frit (because of the colour of the washer), which is NOT the recommended one for eluents of pH<4, nor for my tipe of pump. (It should have been 10 uM)

I found tiny metallic fragmens in the outlet unit, also when opening the inlet fitting of the column.
The column had a void, but I don´t know whether it has been caused by the particulates. (Whatman technician told me that packing material may have been dissolved)

Dionex technician advised me to perform a special wash to remove all the fragments before installing a new column.
The wash is HNO3 3N, which is quite strong.

Anyone suffered a similar problem?
Do you think that the acid wash is adequate?
Column void can be caused by particulates entering the column?

Thank you very much for your time, any ideas will be very welcomed!!!

Best Regards

[rhaefe]

I can see that 0.8mol/L chloride at pH=2.8 will corrode stainless steel. I would replace all ss fritted surfaces with Ti frits.
Years ago I saw something similar in an old HP1090 that was purchased at an auction. While rebuilding most of the flow path and seals and valves I removed the static mixer which was a 4.6x150mm column filled with ss ball bearings (about 2mm in diameter if I remember correctly). The frits on that column were almost completely eaten away and crumbled to dust when I removed them.

[JDiaz]

Thank you very much for your answer, Robert.

The amazing thing is that the same application has been used for years in a Waters HPLC with same column and eluents, but the device is in a 15ºC room (colleague´s lab).
I have to check if Waters HPLC also has a stainless steel frit and if it is in right conditions. Maybe it has a Ti frit?

Right know I have discovered that the guard cartridges I have just received form Whatman also seem to have stainless steel frits. (I have never used them before). So probably I won´t be able to use them!

In addition, the filters that absorb the eluents in the reservoirs are also stainless steel, but maybe they are less sensitive than a 0.5 uM frit?

Thanks a lot!!

[HW Mueller]

The easiest thing might be to replace the Cl- so that one can not get any H+Cl-. One can imagine that slight changes of pH, temp., and SS can produce considerable difference in corrosion here.
It would border on a miracle if particulars caused a void. Besides the normal causes for voids (dissolution as mentioned already, or pressure fluctuations which may cause the formation of fines) it could be possible that the frits are partially eaten away so that stat. phase is lost.

[Bruce Hamilton]

Sinters can be of different Stainless steel alloys, some of which are more resistant to chloride attack than cheap grades.

The suggested use of the nitric acid may also be to try and passivate the system. The sinter will have a very large surface area, and is easily attacked because flow will continuously remove corrosion products.

If you can't remove the chloride from the mobile phase, I'd use different sinter materials, eg the mobile phase reservoir sinters can be glass.

[JDiaz]

Thanks for the answers!

I´ll try opening the outlet of the column, to see if the outlet frit is damaged and could have caused the stationary phase to flow away.

Dionex technician told me the HNO3 3N was a passivating wash, in fact. I will ask him if I can use glass or other material for the reservoir sinters.

I don´t think that replacing Cl would be easy...but if the void has been really caused by outlet frit damage, it might be the only solution.

Thanks again

Best regards

[JDiaz]

Hello everybody!

I´ve checked the outlet frit of the column and it was OK, so I would conclude that, as Whatman´s technician said, the stationary phase has been dissolved. Part of it was inside the outlet fitting.

For preventing this, he adviced me to use a solvent conditioning column, but they sell them as a pack, with an analytical column. I would like to buy a silica simple column to use as solvent conditioning.
Does anyone recommend me a simple, cheap one, maybe from Waters, Agilent, etc?

As no other frit is damaged in the system, it seems that the one that was "eaten away" was of poorer quality, so I´ll continue using my usual eluents, but wont use those frits

Thank you very much!!