Spectrophotometric assay of aliphatic monohydroxamic acids and α-, β-, and γ-aminohydroxamic acids in aqueous medium

Chelating properties of hydroxamic acids with iron(III) were used for the quantitative determination of several monohydroxamic acids. Maximum absorption was obtained at a wavelength of ca. 500 nm for all iron(III)/monohydroxamic acid complexes tested. Determination of the molar extinction coefficient (ϵM) for each complex simplified the monohydroxamic acid assay since a mean ϵM value could be determined for each family of iron(III)/monohydroxamic acid complexes. These results confirmed the influence of the NH2 group in the coordination of α-, β-, and γ-aminohydroxamic acids with iron(III). Finally, this study showed the high sensitivity of the spectrophometric hydroxamic acid assay, with a minimum required concentration of 2.5 × 10−5 to 5.0 × 10−5 mol l−1 as a function of the monohydroxamic acid concerned. The method was validated under biological conditions for Spectrophotometric quantification of an enzyme-catalyzed acyl transfer reaction resulting in hydroxamic acid production.