. Author manuscript; available in PMC: 2008 May 12.

Published in final edited form as: Anal Chem. 2002 Dec 15;74(24):6244–6251. doi: 10.1021/ac026061s

Table 3.

GC-C-IRMS Glutamate Data for the Three Derivatives Tested^a

		Expected ¹³C enrichment		Measured ¹³C enrichment
Sample	Derivative Type	E (ape)	E_l(ape)	δ¹³ C_PDB (per mil)	F (at %)	E (ape)	E_l(ape)
Natural	NAP	0.0000	0.0000	−33.54 ±0.52	1.0744 ±0.0006	0.0000	0.0000
Std 1	NAP	0.0364	0.2368	−1.31 ±0.09	1.1098 ±0.0001	0.0354	0.2303
Std 2	NAP	0.0800	0.5202	−40.45 ±0.19	1.1557 ±0.0002	0.0813	0.5284
Natural	“mixed”	0.0000	0.0000	−30.43 ±0.09	1.0778 ±0.0001	0.0000	0.0000
Std 1	“mixed”	0.0279	0.2368	−2.92 ±0.17	1.1080 ±0.0002	0.0302	0.2570
Std 2	“mixed”	0.0612	0.5202	29.10 ±0.19	1.1432 ±0.0002	0.0654	0.5560
Natural	tBDMS	0.0000	0.0000	−28.29 ±0.22	1.0801 ±0.0002	0.0000	0.0000
Std 1	tBDMS	0.0197	0.2368	−7.93 ±0.06	1.1025 ±0.0001	0.0224	0.2685
Std 2	tBDMS	0.0433	0.5201	16.19 ±0.38	1.1290 ±0.0004	0.0489	0.5866

E = ¹³C enrichment in the entire derivatized molecule; E_l = ¹³C enrichment in the two labeled carbons (C-1 and C-2) in the glutamate; F = the measured ¹³C in the derivatized molecule; NAP = N-acetyl n-propyl ester; TBDMS = t-butyldimethylsilyl ester; and mixed = N-acetyl t-butyldimethylsilyl ester.