A sensitive spectrophotometric method for determination of tris

The paper describes a sensitive spectrophotometric method for qualitative and quantitative determination of Tris, in the 0.1-1.0 μmole range. The procedure is almost identical with that used for histidine. The green-colored reaction product has two absorption peaks with maxima at 422 nm and 640 nm, in contrast to the single peak (540 nm) in the case of histidine. Absorbance and Tris concentration are mutually linear at both wavelengths, but reading conditions are more favorable at 640 nm.