How much corrosion of the HPLC from dichloromethan?

[acerin]

We use dichloromethan for flushing RP columns. The whole system is in dichloromethan just for approx. 20 minutes? Is this somehow dangerous for HPLC system (corrosion)?

And sometimes we continue with hexan. Could be hexane somehow dangerous (do any harm) for columns?

Thanks!

[Jackus]

Do you use really dichlormethane and hexane for washing of reverse phase columns? Is it done routinelly or occasionally when column is clogged?

[acerin]

Just occasionally when column is clogged with fatty matrix.

[Uwe Neue]

Dichloromethane is an organic solvent and not corrosive. It does not attack steel. However, if you have PEEK tubing in your system, you should not use methylene chloride, since it swells and weakens the tubing.

[Bruce Hamilton]

Just one note of caution, given that you are using dichloromethane in systems with reverse phase solvents.

Ensure that you thoroughly flush the system with miscible solvent, as any residual methylene chloride can slowly hydrolyse when water is present, forming HCl, which is corrosive to most stainless alloys.

The hydrolysis is usually fairly slow ( half life of 1 - 2 years in glass at ambient and in the dark ), but can be catalysed by some metals, hence most vapour degreasing grades of methylene chloride are buffered to neutralise any acid that's formed.

If dichloromethane is being used with other normal phase solvents, there usually is no hydrolysis problem,

Please keep having fun,

Bruce Hamilton

[acerin]

Thanks you very much for your valuable opinions. This is my first question to this forum and I am delighted with quick and expert response.

[dblux_]

Dichloromethane is an organic solvent and not corrosive. It does not attack steel. However, if you have PEEK tubing in your system, you should not use methylene chloride, since it swells and weakens the tubing.

Apart from PEEK tubing, piston seals may not resist dichloromethan. For Dionex Summit it is clearly stated in User's manual that material of RP piston seals is not resistant to dichloromethan.

[wulffniedner]

Yes, as most other HPLC vendors we have special piston seals for dealing with normal phase LC.
I also agree with Bruce: We have evidence that dichloromethane and trichloromethane attack stainless steel because of HCl formed by hydrolysis.

Cheers,
Wulff

[HW Mueller]

It certainly would be very informative to see some data on this HCl from CH2Cl2 and CHCl3. Chloroform in a bottle is protected against oxidation which is known to generate phosgene and, I think HCl. But hydrolysis?

[wulffniedner]

E.g.,

Kinetics of hydrolysis of chloroform and bromoform in aqueous solutions

El Din A.M.S.; Arain R.A.; Hammoud A.A.

Desalination, Volume 120, Number 1, 15 December 1998 , pp. 41-51(11)

[HW Mueller]

Finding this one may be difficult, is it possible for you to list a few conditions?

[acerin]

We have evidence that dichloromethane and trichloromethane attack stainless steel because of HCl formed by hydrolysis.

OK. Hydrolysis. But how much corrosion can happen in just 20-30 minutes of exposure to dichloromethan in your experiences? Please note, that we use it just for column cleaning.

[Uwe Neue]

Gee, let us not panick about steel and methylene chloride. Once upon a time in the dark ages, I did plenty of normal phase chromatography, mostly with methylene chloride. My HPLC instruments did not dissolve...

Note that Wulf Nieders citation refers to methylene chloride in water, probably even seawater, since it was published in a journal on desalination. This appears to be just a little bit different than the case of methylene chloride in normal phase chromatography.

[Bruce Hamilton]

Folks,

I only raised the issue of hydrolysis of methylene chloride because of the potential for residual traces in the presence of water in the OP's situation. I also suggested that normal phase operation is very unlikely to encounter the problem. I don't recall shouting "Fire".

The acid corrosion products from hydrolysis of methylene chloride are known issues is some industrial situations, hence the requirement for degreasing grades to be pH buffered, otherwise cleaned metal items can seriously corrode, as will some types of Stainless Steel.

I've seen a seriously-corroded draw-off valve from a Waters 6000A solvent delivery system that was caused by inadequate miscible solvent flushing of the halogenated normal phase before switching to reverse phase, and then not using the system for a few weeks. The pitting was along the surface in contact with the phase interface.

Please keep having fun,

Bruce Hamilton

[Koen Hollebekkers]

From my opinion, most HPLC systems can resist Dichloromethane or Chloroform. There are maybe a few exceptions.

From my experience the problem starts when you want to recycle these solvents (as happens often in GPC). Than corrosion effects will accelerate