Isotope dilution analysis amino acids

Preston, T., Bury, S., McMeekin, B., and Slater, C. (1996a). Isotope dilution analysis of combined nitrogen in natural waters. II. Amino acids. Rapid Commun. Mass Spectrom. 10, 965—968. 

The isotope dilution technique has been employed for Ihe determination of about thirty elements in a variety of matrix materials, Isotopic dilution procedures have also been most widely used for the determination of compounds of interest in organic chemistry and biochemistry, Thus, methods have been developed for the determination of such diverse substances as vitamin D, vitamin B12, sucrose, insulin, penicillin, various amino acids, corticosterone, various alcohols, and thyroxine. Isotope dilution analysis has experienced less widespread application since the advent of activation methods. Continued use of the procedure can be expected, however, because of the relative simplicity of the equipment required. In addition, isotope dilution is often applicable where activation analysis is not. 

Preston et al. [698,699] have described novel approaches to 15N-isotope dilution determination of ammonium and of free amino acids in natural waters, incorporating chemical derivatization and conventional GC-MS analysis. 

Rittenberg, D., and Foster, G. L. (1940). A new procedure for quantitative analysis by isotope dilution, with application to the determination of amino acids and fatty acids. J. Biol. Chem. 133, 737. 

It is worth noting that the term isotope dilution has also been applied to apphcations where the concentration of a compound is determined isotopicaUy rather than by direct chemical determination. The most famihar appHcation is the determination of the magnitude of a blank (pre-existing in an analysis) by adding a known amount of to a sample and determining the decrease from the expected isotopic value of the tracer addition. This concept can also be used in field samples, such as for determining the concentrations of dissolved and combined amino acids. 

Stark T, Justus H, Hofinann T (2006) Quantitative analysis of N-phenylpropenoyl-L-amino acids in roasted coffee and cocoa powder by means of a stable isotope dilution assay. J Agric Food Chem 54 2859-2867... 

Matter B, Malejka-Giganti D, Csallany AS, TretyakovaN (2006) Quantitative analysis of the oxidative DNA lesion, 2,2-Diamino-43,5-di-0-aeetyl-2-deoxy-b-D-erthro-sepentofuranosyl) amino]-5-(2H)-oxazolone (oxazolone) in vitro and in vivo by isotope dilution-capillary HPLC-ESI-MS/MS. Nucleic Acids Res 34 5499-5460... 

For metabolomics studies using IM-MS, electrospray ionization (ESI) is commonly used and the quantitative analysis will be different than the Ni. With ESI, internal standards, standard addition, isotope dilution, or external calibration curves are common practices for relative quantitative analysis. An example of ESI-IM-MS quantitative analysis was demonstrated for 20 phenylthiohydantoin (PTH)-derivatized amino acids, the final products in the Edman sequencing process of peptides and proteins. Detection limits for these amino acid derivatives ranged from 1.04 to 3.52 ng (less than 17 pmol).<" ° Quantitative analysis has not yet been established with ESI-IM-MS for applications to metabolomics. 

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