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Rapid Commun Mass Spectrom

Title:		Optimisation of derivatisation procedures for the determination of delta13C values of amino acids by gas chromatography/combustion/isotope ratio mass spectrometry
Author(s):		Corr LT; Berstan R; Evershed RP;
Address:		"Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK"
Journal Title:		Rapid Commun Mass Spectrom
Year:		2007
Volume:		21
Issue:		23
Page Number:		3759 - 3771
DOI:		10.1002/rcm.3252
ISSN/ISBN:		0951-4198 (Print) 0951-4198 (Linking)
Abstract:		"Compound-specific stable carbon isotope analysis of amino acids by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) is a highly selective and sensitive method for probing the biosynthetic/diagenetic pathways, pool size and turnover rates of proteins, previously intractable to bulk isotope analyses. However, amino acids are polyfunctional, non-volatile compounds which require derivatisation prior to GC analysis. While a wide range of derivatives exist for the GC analysis of amino acids only a handful have been utilised for their GC/C/IRMS analysis. Significantly, none of those derivatives currently employed appear completely satisfactory and a thorough assessment of their relative utility is lacking. Seven derivatives (three previously reported and four novel) for obtaining delta(13)C values of amino acids via GC/C/IRMS analysis were compared. More specifically, standard mixtures of 15 protein amino acids were converted into N-acetylmethyl (NACME) esters, N-acetyl n-propyl (NANP) esters, N-acetyl i-propyl (NAIP) esters, N-trifluoroacetyl-i-propyl (TFA-IP) esters, N-pivaloyl methyl (NPME) esters, N-pivaloyl n-propyl (NPNP) esters and N-pivaloyl i-propyl (NPIP) esters. Each derivative was assessed with respect to its applicability to carbon isotope determinations of all the common alpha-amino acids, reaction yield, chromatographic resolution, stability, analyte-to-derivative carbon ratio, kinetic isotope effects and errors associated with their carbon isotope determinations. The NACME derivative was concluded to be the preferred derivative mainly due to the highest analyte-to-derivative carbon ratio being achieved, resulting in the lowest analytical errors for amino acid delta(13)C value determinations, ranging from +/-0.6 per thousand for phenylalanine, leucine and isoleucine to +/-1.1 per thousand for serine and glycine"
Keywords:		"*Algorithms Amino Acids/*analysis/*chemistry Carbon Radioisotopes/*chemistry Chromatography, High Pressure Liquid/*methods Hot Temperature Quality Control Spectrometry, Mass, Electrospray Ionization/*methods;"
Notes:		"MedlineCorr, Lorna T Berstan, Robert Evershed, Richard P eng Wellcome Trust/United Kingdom Research Support, Non-U.S. Gov't England 2007/11/09 Rapid Commun Mass Spectrom. 2007; 21(23):3759-71. doi: 10.1002/rcm.3252"