Figure 2: Chromatogram overlay showing the ion intensity of metabolites. [A] Total Ion Chromatogram for Jurkat cells rinsed with either 0.3% ammonium formate or 0.3% ammonium acetate. [B] Total Ion Chromatogram for 6-8 min. shows an increased peak intensity for the caffeine-d3 and tryptophan-d3 internal standards for cells rinsed with 0.3% ammonium formate. Retention time reproducibility for internal standards, caffeine-d3 and tryptophan-d3 was 0.3 seconds over the entire chromatographic run. Peak Area reproducibility for internal standards, caffeine-d3 and tryptophan-d3 was 3.6 %CV and 5.8 %CV.