Fig. S3.
GC-IRMS chromatogram of 13C isotope measurements of d+l glyceric acid (peak 6) and 2-methylglyceric acid (peak 5) after initial purification from a Murchison extract by ion chromatography (both compounds analyzed as TMS derivatives). The β-alanine (peak 7) is an internal standard. Peaks 3 and 4 are pulses of CO2 reference gas.