[Alexanderke]

Hey,

i'm analysing an article where they analyse ranitidine HCl (RHCl) using redox reactions. I understand the article and how they work but i don't realise what the exact reaction mechanism is. It involves two stages oxidation ( said in article but not 100% sure what this means, i guess 2 redox reactions following each other) of Ranitidine HCl with excess N-bromosuccinimide (NBS) and estimation of excess oxidant using a known excess of dye ( amaranth dye). The remaining dye will be measured colorimetrically at suitable λ_max.

To a 10 ml flask containing the drug they will add HCl , NBS and a little bit of KBr. Later they will add the dye.

So i was thinking RHCl would have a redox reaction with NBS using the acid for pH.The s-oxide of ranitidine will be formed but what will hapen to the NBS? And i can't find a use for the KBr :/
It should accelerate the reaction. 1 mol RHCL needs 6 mol NBS and the remaining NBS will reduce the intensity of the dye color.
In another article they use KBr and BrO₃^- to form Br₂ which will react with RHCl. But then the NBS from my article won't be used as oxidans.

Thanks in advance for people who can help me with this.

PS: Article i'm analysing : A.S. Amin et Al. / Spectrochemica Acta Part A 59 (2003) 695-703: Utility of oxidation-reduction reaction for the determination of ranitidine hydrochloride....