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. Author manuscript; available in PMC: 2014 Apr 29.
Published in final edited form as: Biol Mass Spectrom. 1992 Oct;21(10):486–490. doi: 10.1002/bms.1200211004

Figure 2.

Figure 2

The relationship between the expected 13C enrichment (at.% excess) in the carboxyl leucine carbon and the observed 13C enrichment in N-acetyl n-propyl (NAP)–leucine (11 carbon atoms) measured by capillary GC/combustion IRMS. The equation for the line is Y = 0.0962X + 0.0001, r=0.998 (n = 21), and the 99th percentile confidence intervals are given by the dotted lines. The delta (δ) values versus PDB for NAP-leucine are shown in parentheses (mean ± SD) compared to a measured value of −27.71 ± 0.12 for natural NAP–leucine.