Strychnine Reagent Testing
Following Keeper Trout’s presentation on Strychnine at Garden States last weekend, one attendee queried if there any reagent tests for strychnine. Keeper has recently emailed the EGA team with some more detail around this question:
“A problem with many assays is lack of specificity. Dragendorff's for example says an alkaloid is present but that is not very meaningful if a person is looking for an adulterant of one alkaloid with another one. Even just iodine vapor is as useful for that application. With prior TLC separation and reference standards those actually CAN work* if using a TLC approach* but the need for a reference standard trips up many people.
A nitroprusside reagent is usually used to show a temporary orange chromophore for strychnine but I noticed that Kenneth Lohr produced what appears to be a bunch of false positives using it with a porcelain spot test approach (he was a Missouri pharmacist who taught himself how to do spot analysis that commonly do not agree with the results of actual analysts) so I did not want to suggest that when speaking. There does seem to be a way to modifying it though (using a tin compound) so hopefully analysts there can employ the modification in developing a simple colorimetric spot test approach. I'll have a paper to you asap on this but am having some computer challenges this AM. Hopefully updates will resolve that.
Karawya, et al. 1975 appears to be adaptable for spot testing. Ideally this is used with TLC for separation of mixtures but it would be worth testing on a known drug mixture containing added strychnine to evaluate the potential of cross reactivity and ability to give yes or no answers with drug mixtures in spot testing. The modification in this paper might help avoid whatever Lohr was having problems with. It does need some real world testing before recommending it for use. Strychnine is fairly easily obtained in gopher baits and in products intended to be given to fighting cocks. Dr. Blue is a common brand. The first would need extraction but the second are veterinary quality materials that might work fine as they are for reference standards.”
Karawya, M., Hifnawy, M. & Dahawi, H. (1975) Colorimetric Assay of Strychnine and Brucine in Nux Vomica. Journal - Association of Official Analytical Chemist, 68(1):85-7.
