By Anonymous on Thursday, August 21, 2003 - 12:30 pm:
Hello,
Our lab is working on getting a method going for the analysis of Diquat and Paraquat in soil or plant tissue. The only reference I've found comes from Chichila and Gilvydis, Journal of AOAC International, Vol. 76, No. 6, 1993. The LC mobile phase for this method requires dissolving 5 grams NaCl in 600mL water adjusted to pH 2.2 with 1M HCl, then adding 400mL ACN. I am concerned about stainless steel corrosion from the chloride. The authors claim that "the presence of chloride ions in the mobile phase appears to be necessary for the representative and reproducible chromatographic separation of paraquat and diquat in sample residues...."
Is anyone using this method? Have you had problems with using sodium chloride or have you found an alternative? Is there another method in the literature that I am missing? Much thanks.
By Anonymous on Thursday, August 21, 2003 - 03:44 pm:
You can get good peak shape for the quats on a modern high-purity silica column. Then you do not need to go to such an acidic pH as the authors suggested, and you don't need to dissolve your HPLC instrument in HCl.
By B.Buglio on Friday, August 22, 2003 - 05:28 pm:
There are many reference for this separation on
the Waters Web site. There is also an EPA method
available. Most of these are ion pairing methods.
By Russ on Sunday, August 24, 2003 - 10:59 am:
Haven't actually tried this but saw it not too long ago in a Supelco publication. It is not ion pair. If you try it, let me know how it works.
http://www.sigmaaldrich.com/Brands/Supelco_Home/TheReporter/Liquid_Chromatography/Reporter_20_9_new_appl.html
By Anonymous on Tuesday, August 26, 2003 - 11:51 am:
Thank you all for the suggestions and references. That column from Supelco is very interesting. Not sure if the boss will buy one, but I'll let you know how it works if I get to try it.
Regards.