The reverse phase chromatograph is capable of highly reproducible (better than 5% precision for D/L ratios of most amino acids) stereoisomeric separations of amino acids with sub-picomole detection, sufficient for analysis of single microfossils (foraminifera and ostracodes). Analytical reproducibility for nine amino acid D/L ratios in fossils with a broad range of ages is typically better than 5%. Aspartic acid and glutamic acid D/L ratios are the most consistently well-resolved and reproduced, with analytical variations of <3%. Analytical drift and background are monitored by routine analysis of intra-laboratory standards. Compatibility of results is assessed by analysis and reporting of Inter-laboratory Calibration Standards (
ILC; Wehmiller, 1984). D/L ratios measured in the three
ILC standards overlap with D/L ratios measured previously by GC-based laboratories in 17 out of 18 cases, when considering the ±1 sd analytical errors (see Kaufman and Manley (1998) for more information).
References
Kaufman, D.S., and Manley, W.F., 1998, A new procedure for determining enantiomeric (D/L) amino acid ratios in fossils using reverse phase liquid chromatography: Quaternary Science Reviews 17, 987-1000.
Wehmiller, J.F., 1984, Interlaboratory comparison of amino acid enantiomeric ratios in fossil Pleistocene mollusks: Quaternary Research 22, 109-120.
