Rapid automated ion-exchange analysis of plasma tyrosine and phenylalanine with data print-out

A rapid automated method with data print-out is described for quantitation of plasma phenylalanine and tyrosine from 0.100 ml of sample. The system uses the Rank-Hilger Chromaspek amino acid analyser linked to a Digico M16E computer. Amino acid concentration up to 3000 microM can be quantitated without repeat dilutions and assessment of precision at the 500 microM level, produced coefficients of variation of 2.2% for tyrosine and 2.5% for phenylalanine. Recovery determinations from a plasma pool gave a mean recovery of 99.4% for tyrosine and 99.7% for phenylalanine. Correlation with established fluorimetric techniques was excellent (r = 0.986 for tyrosine, r = 0.976 for phenylalanine). By using the same resin column for both the rapid separation of tyrosine and phenylalanine, and the standard physiological fluid separation, full analysis capability is retained with easy interchange between the two systems.