Production of Salkowski Reagent From NaOH, FeCl3, NH4ClO4, and HCl

Salkowski reagent is often used tool for quantifying the presence of indole-3-acetic acid (IAA) among other indoles. It is a mixture of perchloric (HClO₄) at 35% concentration and ferric chloride (FeCl₃) at a 0.5M concentration (Gang, Sharma and Saraf). Salkowski reagent turns pink in the presence of IAA due to a reaction that forms an IAA complex with Fe³⁺ and its subsequent reduction (Kamnev, Shchelochkov and Perfiliev). Although one can order perchloric acid from various sources, costs or restrictions may prevent the direct order of perchloric acid. We developed this protocol to produce Salkowski reagent using readily available lab chemicals.