Isolation of Underivatized Amino Acids for Radiocarbon Analysis Using a Porous Graphite Column.

We developed a method for isolation and purification of individual underivatized amino acids for compound-specific radiocarbon analysis. Our method employs a semipreparative porous graphitic carbon column that allows for separation and isolation of all proteinogenic amino acids in a single step. To minimize contamination, we utilized a mixed-mode ion-exchange column to further purify the isolated amino acid fractions. Radiocarbon measurements of standard amino acids processed with this method resulted in F14C values closely aligned with their original F14C values. From these measurements, we calculated the blank contribution to 1.0 ± 0.3 μg C with F14C = 0.6 ± 0.12, rendering this approach suitable for ultrasmall samples with enhanced measurement reliability.