Diazotised 4-Nitroaniline as a Chromogenic Reagent for the Determination of Indole Derivatives in Certain Pharmaceutical Preparations

Abstract

A sensitive colorimetric method has been devised for microdetermination of six indole derivatives; ergotamine tartrate, methylergometrine maleate, dihydroergocornine methanesulphonate, dihydroergocristine methanesulphonate, dihydroergocryptine methanesulphonate and pindolol, both in pure form and in pharmaceutical preparations. The method is based on the reaction of indole moiety with diazotised 4-nitroaniline in buffer solution of pH 6 to produce a stable yellow monoazo dye. Beer's law is obeyed over final concentration ranges 8–32 μgm1^?1 for ergotamine tartrate, 4–48 μgml^?1 for methylergometrine maleate, 8–56 μgml^?1 for dihydro-ergot alkaloids and 1–10 μgml^?1 for Pindolol with apparent molar absorptivity range (7.62 × 10³?2.61 × 10⁴) 1.mole^?1.cm^?1. A study has been made to determine the optimum conditions of the colour reaction.