Differential spectrophotometric determination of tyrosine and tryptophan in pharmaceutical amino acid solutions.

A method is proposed for the simultaneous determination of tyrosine and tryptophan in solutions by differential spectrophotometry. The concentrations are calculated from the measurement of the absorbance of the amino acid mixture in an alkaline medium and from the differential absorbance of the alkaline solution against the acid solution at 294.4 nm. A comparison with three other well-known methods is discussed.