Chromatography Forum

Thanks to Wulff I got hold of the abstract of the article in "Desalination" which he cited above, regarding hydrolysis. The authors talk of base catalysis, of dihalocarbene intermediates, and of ~18kcal activation energy. Thus I would expect that you dissove your silica before the stainless steel. (In base you wouldn´t have any HCl. I havn´t seen Cl- do anything.)
Bruce, I think you should consider yourself extremely lucky to see pitting?

Lucky?, No. Waters spares were/are very expensive here.

The yellow-gold colour of the acidic ferric solution was immediately obvious, as the 6000A was primed each day by purging 10 mls of solvent into the supplied clear glass syringe.

I've no wish to turn this into some dramatic event that all users should worry about, but I thought reminding the original poster might be a good idea, given they were regularly switching between aqueous and methylene chloride, which may be an uninhibited grade.

The wet hydrolysis reaction is catalysed by iron and other metals, so
any wet dichloromethane sitting in metal crevices has the potential to induce corrosion.

Anyone who has worked industrial scale halogenated solvent degreasing will be aware that any rust and water in/on the solventvrapidly remove any acid acceptance tolerance of such solvents, and metal corrosion starts to appear almost immediately the inhibitors/buffers are depleted.

The corrosion potential of wet methylene chlride is probably due to the relatively high solubility of methylene chloride in water ( about 1.8% @ 20C - twice that of chloroform ), combined with the steep decrease of solubility in water with increasing temperature, the density, and the affinity of any separated material for metal surfaces.

I'm wondering whether the Digg mantra ( " provide photo, or it didn't happen" ) is becoming more pervasive.

Please keep having fun,

Bruce Hamilton

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

Below 2 links with piston seals solvent resistance specification:

http://www.optimizetech.com/opti-shop/i ... th=3_21_95


http://www.hplc-asi.com/products/replac ... _seals.htm


I wouldn't stress UHMW-PE piston seals with dichloromethane.

Bruce, I have no doubt that you saw what you mentioned, no need for pictures. I am just wondering why I havn´t seen anything even when using liters of dichloromethane with acetic acid in it, or without, H2O often in contact also.... Then there are these recommendations of many column manufacturers to use these solvents in cleaning steps. Also, there are others here that have not seen it, for instance Uwe, whose contact to chromatography has been much more intense than mine.

....Sure would like to find out, though, under what conditions and what Fe catalyze the hydrolysis.