Some observations on the spectrophotometric determination of amino acids via interaction with p-benzoquinone

Abstract

Spectrophotometric quantitative determination of amines and sulfa drugs via interaction with p-benzoquinone was extended to determination of amino acids, whereby the colored products obtained display maximum absorption at λ = 490–500 nm, E1 cm1% in the range 160–480, and a concentration range of 1.5–34.0 μg/ml. The effects of time, concentration, temperature, and cooling on the nature of the reaction product were investigated. The reaction proved to be irreversible. A monosubstituent compound is more easily formed in the presence of excess p-benzoquinone. A linear relation between the formation constant (Kf) and pKα for the tested amino acids has been observed. Determination of adrenaline by this method is considered to offer an indirect means of determination of tyrosine.