title: Spectrophotometric determination of tryptophan by reaction with nitrous acid.
abstract: The heterocyclic nucleus in tryptophan is oxidised by nitrous acid at elevated temperature to produce a phenolic intermediate which further reacts with nitrous acid to form a nitro compound that has a golden yellow colour in alkaline medium. The maximum absorbance is obtained at 400 nm with maximum molar absorptivity of 9.44 x 10(3) l.mole(-1). cm(-1). Derivatives of tryptophan such as indole-3-acetic acid, tryptamine and tryptophanamide, as well as indole, produce the same colour, but some others, e.g., 5-hydroxytryptamine and 5-hydroxyindole-3-acetic acid do not give the colour reaction. A plausible mechanism is proposed to explain this behaviour.
authors.affiliation: Department of Chemistry, Rani Durgavati University, Jabalpur 482001, India.
authors.forename: K K
authors.initials: KK
authors.lastname: Verma
authors.forename: A
authors.initials: A
authors.lastname: Jain
authors.forename: J
authors.initials: J
authors.lastname: Gasparic