After centrifugation, the supernatant must be completely removed or the remaining bismuth nitrate will cause an increased background. Proteins can precipitate in the presence of Dragendorff reagent. It is recommended to remove the proteins from the samples before addition of the reagent.
Experiment 8: Pyrrolizidine Alkaloids (Methyl Orange Method)
Protonation of pyrrolizidine alkaloids in chloroform solution with acetic acid and their stoichiometric reaction with aqueous methyl orange lead to the formation of yellow complex that can be detected at 525 nm (Birecka et al., 1981).
Was this article helpful?