Sodium Perchlorate Mobile Phase

[Chris]

I have a method that uses a 1%w/v sodium perchlorate in 40:60:1 water/acetonitrile/acetic acid mobile phase. I have heard some bad stories about the use of sodium perchlorate in mobile phase (explosions etc). Has anyone got any experience of using sodium perchlorate and what special precautions should be taken.

Thanks

[Mark Tracy]

I have used perchlorate a little, and one of my colleagues here uses it often. The biggest problem is that it is an environmental hazard, and is expensive to dispose of. In the context of HPLC, sodium perchlorate is safe, probably less hazard than the flammable solvents. The main precaution is to not let perchloric acid solutions go to dryness.

Where perchlorate explosions are a risk is in the use of hot perchloric acid for sample digestion. There, concentrated vapors in contact with metal fume hoods can form explosive salts; special hoods are required. I used to digest tissue with a boiling nitric/perchloric/sulfuric mix and never had an explosion. (Milkfat didn't exactly explode, but the shooting flames were quite colorful.)

The best person to talk to is your company's Environmental Health and Safety officer. There may be local rules that need to be followed.

[rhaefe]

Agree with Mark:

I have done some work with sodium perchlorate in the past (ion exchange chromatography, 100% aqueous, up to 1mol/L sodium perchlorate) and never encountered any problems. Sodium perchlorate is much more stable than sodium chlorate or ammonium perchlorate.
That said I would definitely avoid any salt build-up due to leaks and subsequent evaporation. Other than that I don't see a problem. Your overall concentration of perchlorate is low and you have 40% water present.

[rhaefe]

Oh and I forgot: to get more info on perchloric acid and perchlorates contact GFS Chemicals (www.gfschemicals.com)

[Bruce Hamilton]

I used sodium perchlorate in mobile phase recently, as the USP method for Ramipril related substances specifies 0.2%. As others note above, it's a good idea to not allow perchlorate-containing solutions to dry, and also ensure there are no leaks/crystals at screw thread connections.

I just rinse the system with 90:10 water/acetonitrile after the runs. Sodium ( and most alkali metal and alkaline earth ) perchlorates are much less sensitive to shock/explosion than the heavy metal perchlorates, and disposal is usually simply dilution with water to less that 0.002% perchorate, and down the drain ( if lcoal regulations allow ).

Bruce Hamilton

[Chris]

Thanks, sounds ok then. We have a automated 95%water flush after all HPLC runs that contain buffers anyway so the risk of buffer preciptation should be minimal.

[Wen Jiang]

One extra comment.
In a previous study by Lindner et. al., they use one eluent containing 70% acetonitrile, 0.015 M TEAP and 0.68 M sodium perchlorate for gradient elution. Details can be found in J. Chromatogr. A 743(1996) 137-144.