Chromatography Forum

Does anybody know of a manufacturer who makes inert syringe needles?

Made out of nickel, or with a surface treatment. I have a problem with heavy corrosion on steel needles due to H2S which is entrapped within a liquid sample.

It should be easy to get rid of H2S prior to chromatography. But what does H2S do to stainless? Your HPLC is not stainless?
(Do you know of the chap at the School of Mines, Golden, CO, who went to the eternal hunting grounds by mishandling H2S?)

Well I'm actually doing gas chromatography, but I thought (maybe mistakenly) that I would have better luck inquiring about needles in the HPLC forum.

Can't get rid of the H2S prior to injection because that's part of what we're analyzing for.

The H2S (along with some sulfuric acid) is forming iron sulfide in the form of a black powder.

It turns out we can get the needles silcosteel lined which should stop the corrosion. When I made the post I wasn't sure that would be possible! I'm surprised that there doesn't seem to be a supplier of syringes that makes the needles out of different materials (nickel alloy for example).

Have you tried Hamilton ?, I'm pretty sure that I have seen them offering platinum needles. Depending on what kind of syringe you have you can jury rig a completely inert needle out of a piece of uncoated fused silica.

Peter

Just out of curiosity: How does H2S oxidize Fe°? Is Cl- involved?

I think the mechanism is complex and isn't well understood. From a quick google search:

Hydrogen sulfide is a weak acid when dissolved in water, and can act as a catalyst in the absorption of atomic hydrogen in steel, promoting sulfide stress cracking (SSC) in high strength steels. Polysulfides and sulfanes (free acid forms of polysulfides) may be formed when hydrogen sulfide reacts with elemental sulfur. These sulfanes are produced along with other gaseous constituents. As pressure decreases up the production tubing, the sulfanes dissociate and elemental sulfur precipitates, which can cause plugging.

Iron sulfides are often formed from corrosion reactions, and can be important in corrosion control, especially at lower temperatures and low H2S partial pressures, where a protective film often forms.

Corrosion products include black or blue-black iron sulfides, pyrite, greigite, mackinwaite, kansite, iron oxide (Fe3O4), magnetite, sulfur (S), and sulfur dioxide (SO2).

http://octane.nmt.edu/waterquality/corrosion/H2S.htm

Is it absolutely certain that your canula didn´t get in contact with HCl?