Results are presented of a comparison of the amino acid (AA) δ(13)C values 
obtained by gas chromatography-combustion-isotope ratio mass spectrometry 
(GC/C/IRMS) and liquid chromatography-isotope ratio mass spectrometry (LC/IRMS). 
Although the primary focus was the compound-specific stable carbon isotope 
analysis of bone collagen AAs, because of its growing application for 
palaeodietary and palaeoecological reconstruction, the results are relevant to 
any field where AA δ(13)C values are required. We compare LC/IRMS with the most 
up-to-date GC/C/IRMS method using N-acetyl methyl ester (NACME) AA derivatives. 
This comparison involves the analysis of standard AAs and hydrolysates of 
archaeological human bone collagen, which have been previously investigated as 
N-trifluoroacetyl isopropyl esters (TFA/IP). It was observed that, although 
GC/C/IRMS analyses required less sample, LC/IRMS permitted the analysis of a 
wider range of AAs, particularly those not amenable to GC analysis (e.g. 
arginine). Accordingly, reconstructed bulk δ(13)C values based on 
LC/IRMS-derived δ(13)C values were closer to the EA/IRMS-derived δ(13)C values 
than those based on GC/C/IRMS values. The analytical errors for LC/IRMS AA 
δ(13)C values were lower than GC/C/IRMS determinations. Inconsistencies in the 
δ(13)C values of the TFA/IP derivatives compared with the NACME- and 
LC/IRMS-derived δ(13)C values suggest inherent problems with the use of TFA/IP 
derivatives, resulting from: (i) inefficient sample combustion, and/or (ii) 
differences in the intra-molecular distribution of δ(13)C values between AAs, 
which are manifested by incomplete combustion. Close similarities between the 
NACME AA δ(13)C values and the LC/IRMS-derived δ(13)C values suggest that the 
TFA/IP derivatives should be abandoned for the natural abundance determinations 
of AA δ(13)C values.