Objectives: To determine the origin of 15N-labeled phenylalanine in microbial metabolic flux analysis using 15N as a tracer, a method for measuring phenylalanine δ15N using HPLC coupled with elemental analysis-isotope ratio mass spectrometry (EA-IRMS) was developed.
Results: The original source of the 15N-labeled phenylalanine was determined using this new method that consists of three steps: optimization of the HPLC conditions, evaluation of the isotope fractionation effects, and evaluation of the effect of pre-processing on the phenylalanine nitrogen stable isotope. In addition, the use of a 15N-labeled inorganic nitrogen source, rather than 15N-labeled amino acids, was explored using this method.
Conclusions: The method described here can also be applied to the analysis of metabolic flux.
Keywords: Elemental analysis-isotope ratio mass spectrometry (EA-IRMS); High-performance liquid chromatography; Metabolic flux analysis; Phenylalanine; δ15N.