On the specificity of the folin and lowry reagents for amine derivatives.

Reactivities of several amine derivatives with the Folin and Lowry reagents were examined. Tertiary amines reacted with the Folin reagent to produce a blue color, and secondary amines having a 2-hydroxyethyl group reacted with the Folin reagent only in the presence of Cu²⁺, i.e., with the Lowry reagent. On the other hand, primary and quarternary amines and amine N-oxides produced no color with either reagent. Reactivities of tertiary amines were greatly influenced by the nature of the N-substituted groups, and the color yield of those forming stable chelate complexes with metals was strongly inhibited by the presence of Cu²⁺, indicating that the formation of a stable complex with Cu²⁺ reduces the reactivity of tertiary amino nitrogen. The requirement of Cu²⁺ for the color development with secondary amines having a 2-hydroxyethyl group may be due to the formation of weak chelate complex with Cu²⁺.