The AAGL analyzes the amino acid composition and the extent of amino acid racemization in a variety of fossils types (mollusks, ostracodes, foraminifera, bone, egg shells, and teeth), and in non-fossil materials. Samples are analyzed by either ion exchange (IE-LC) or reverse phase (PR-LC) liquid chromatography, depending on sample size and age-calibration strategy. IE-LC separates nine common amino acids, including isoleucine and alloisoleucine, which is used to measure the extent of epimerization (racemization). RP-LC separates D and L enantiomers of several amino acids including aspartic acid and glutamic acid, which are most commonly used for geochronology. Both procedures yield quantitative estimates of amino acid concentrations by comparison with internal spikes of non-protein amino acids. Samples are pretreated using conventional mechanical and chemical procedures. Following sample pretreatment, amino acids are analyzed either prior to sample hydrolysis to isolate the naturally free amino acid fraction, or following standard hydrolysis. Hydrolysis results in the conversion of any asparagine in fossil proteins to aspartic acid, and glutamine is transformed to glutamic acid.
