Determination Of Tryptophan In Pharmaceutical Formulations And Beer By Enhancement Of Tryptophan-Fluorescence Response With Fluorescein And Potassium Hexacyanoferrate(Iii)

Tryptophan is an essential amino acid for humans with a significant role in cell metabolism. Depletion of tryptophan in the human body may contribute to diseases and development of disorders in humans. The native fluorescence of tryptophan alone was, however, not very sensitive enough in our studies resulting in a limitation of reliability and sustainability of tryptophan analysis. We found that fluorescein as fluorescent dye and potassium hexacyanoferrate(III) as oxidant successfully enhanced the tryptophan-fluorescence response signal to such an extent that a novel proposed enhancement tryptophan-fluorescence method with modification using these inexpensive reagents was successfully applied for the determination of tryptophan in pharmaceutical capsules and beer with very good recoveries and relative standard deviation. The recoveries agreed very well with the certified amount labeled for tryptophan in pharmaceutical formulations with very good recoveries between 99.9 and 102.8 % and a relative standard deviation of less than 0.5% (n = 5). The recoveries for the determination of tryptophan in beer were between 93.7 and 95.1 % with a relative standard deviation of less than 0.5% (n = 5).