Chromatography Forum

Melarsomine, anamial drug treats dog heartwoom, is unstable (hydrolysis) in aq solution. Anybody has input of the LC method that can be used to determine melasrsomine? Thanks.

JL

Hard to believe that a something that isn't water stable could be a drug unless it is a prodrug. That being said, have you looked into normal phase options?

Also, are you sure this is water unstable? Based on the literature out there for making it, the final synthesis step can be performed in water and directly lyophilised to final product:

"step 4: the dry or wet melarsen oxide dihydrate is suspended in water and then brought into contact with cysteamine hydrochloride to give melarsomine dihydrochloride, which may thereafter be recovered in solid form by crystallisation at lowtemperature or the like, followed by drying. Advantageously, the sterile melarsomine dihydrochloride may be recovered by lyophilisation and packaged."

http://www.patentgenius.com/patent/5635499.html

Perhaps stability is pH dependent?

In the instructions for use it is stated that it should be reconstituted in water and holds its potency for 24 h if refrigerated.
This should be a perfect candidate for HILIC.
Here is a method for melamine and metformine that should be useful. pH in the note is 6.8 but any pH below 8 can be used for pH above 8 use the polymeric version of the column (ZIC-pHILIC)

http://www.merckmillipore.com/chemicals ... 113-XX-IMG
or click the SeQuant banner above.

http://www.sequant.com/files/documents/ ... nidine.pdf

Thank you all. It is kind of prodrug, which quickly reaches dissociaiton eq in aq medium by losing one cysteamine moiety. I have RP UPLC method that detected 2-3 peaks even I preppared sample in organic solvent and kept it cool. The solubility of the compound in most orgainc solvents is low. But, I might have to try normal phase without mouch option.

Have you obtained an NMR to verify sample purity?

You can do this in non-aqueous hydrogen-bonding mode on SHARC 1 columns, similar to compounds in the following brochure:
http://www.sielc.com/upload/file/pdf/SHARC_1.pdf

Contact me if you have questions.

Low resolution NMR results appeared OK.

Vlad,
Thanks for the information. We might want to try SHARC or HILIC kind columns. BTW, in the brochure the mobile phase has 95%MeCN, 5%MeOH with 0.5% Formic acid and 0.05% AmFm. Can you tell me what is "AmFm"?
Thanks.

AmFm - ammonium formate
AmAc - ammonium acetate