Converting A/I values (ion exchange) to D/L values (reverse phase) for amino acid geochronology

Abstract

Several analytical techniques have been used in amino acid geochronology to measure the relative abundances of D-and L-enantiomers. During the past two decades, reverse-phase (RP) liquid chromatography has become most common, whereas ion-exchange (IE) liquid chromatography was widely used prior to the mid-1990s. This study is based on intra-lab paired analyses of RP and IE liquid chromatography to mathematically convert A/I (alloisoleucine:isoleucine) values determined with IE to corresponding D/L values for comparison with new RP results. Pooled results of 340 paired IE and RP analyses show that A/I values can

Upper Pleistocene parabolic ridges (i.e. ‘chevrons’) from the Bahamas: Storm‐wave sediments or aeolian deposits? A quantitative approach

“…Finally, knowing that further procedures would use dilute HCl to remove 30% of the sample mass to reduce the possibility of contamination by cements and organic residues on grain surfaces, a minimum weight of powder of 50 g was chosen. Samples were sent to the Amino Acid Geochronology Laboratory of the Northern Arizona University where the amino-acid content was measured by reverse phase high-performance liquid chromatography (Kaufman & Manley, 1998;Whitacre et al, 2017). The D/Lglutamic-acid (Glu) ratios were found to be the most appropriate ratios (Rutter et al, 1979;Rutter, 1985;Hearty & Kaufman, 2009) to date oolitic sediments, and are the only ones used in this study.…”

“…The D/Lglutamic-acid (Glu) ratios were found to be the most appropriate ratios (Rutter et al, 1979;Rutter, 1985;Hearty & Kaufman, 2009) to date oolitic sediments, and are the only ones used in this study. The conversion method of Whitacre et al (2017) was applied to the present data to calculate the Alloisoleucine/Isoleucine (A/I) values in order to compare them with the database generated in the Bahamas (Hearty & Kaufman, 2000.…”

Amino acid racemization and its relation to geochronology and archaeometry

“…Before the mid‐1990s, IEC was widely used for the determination of d / l enantiomers . A recent paper reports converting the IEC values for allo‐isoleucine:isoleucine to corresponding HPLC d / l values for comparison, finding correlations for Asx, Glx, and others .…”

“…Detection was by fluorescence (230 nm excitation and 445 nm emission). Used with permission from reference [75] Before the mid-1990s, IEC was widely used for the determination of D/L enantiomers [81]. A recent paper reports converting the IEC values for allo-isoleucine:isoleucine to corresponding HPLC D/L values for comparison, finding correlations for Asx, Glx, and others [81].…”

“…Before the mid‐1990s, IEC was widely used for the determination of d / l enantiomers . A recent paper reports converting the IEC values for allo‐isoleucine:isoleucine to corresponding HPLC d / l values for comparison, finding correlations for Asx, Glx, and others . Regression equations were provided for conversion, enabling the large literature base of AAR results from IEC to be compared and integrated with AAR results from RP chromatography .…”