ABSTRACT
A method for the simultaneous quantitative determination of tryptophan and tyrosine in synthetic peptides by second-order derivative diode-array spectroscopy is reported. The method does not require hydrolysis of the peptides or a derivatization reaction; the sample is dissolved in 0.1 N NaOH and directly scanned between 262 and 264 nm to detect tyrosine and between 304 and 306 nm to detect tryptophan. From these results the peptide content of the synthetic sample can be easily calculated in a very simple and fast way. The results obtained by the described method with several peptides are compared with those obtained by classical high-performance liquid chromatographic analysis of amino acids after peptide hydrolysis. A very good correlation was found both for the tryptophan/tyrosine molar ratio and the peptide content.
Subject(s)
Peptides/analysis , Tryptophan/analysis , Tyrosine/analysis , Amino Acid Sequence , Chromatography, High Pressure Liquid , Hydrolysis , Molecular Sequence Data , Spectrophotometry, UltravioletABSTRACT
A simple and rapid procedure for quantitation of Calcium Leucovorin and parabens simultaneously in lyophilized ampoules formulation by "zero crossing" first-order derivative spectroscopy was developed. The ampoules content was dissolved in a mixture water/ethanol (50/50) and first-derivative spectra were recorded. The absolute values of the derivative at 312 nm for the determination of Calcium Leucovorin and between 244 and 246 nm for the determination of parabens were measured. The method is linear, quantitative and reproducible.
