Age estimation from aspartic acid racemization of root dentin by internal standard method

Area of Science:

• Biogeochemistry
• Analytical Chemistry
• Forensic Science

Background:

• Aspartic acid (Asp) racemization is a method for age estimation.
• Internal standards are crucial for validating analytical measurements.
• D-Methionine (D-Met) and D-norleucine (D-Nleu) were evaluated as potential internal standards.

Purpose of the Study:

• To investigate the application of the internal standard method for age determination using aspartic acid racemization.
• To validate derivatization and gas chromatographic measurements with internal standards.
• To assess the reliability of D-Met as an internal standard for D- and L-Asp quantification.

Main Methods:

• Calibration plots were constructed using standard amino acids and internal standards.
• Gas chromatography was employed for analyzing amino acid enantiomers.
• D-/L-Asp ratios were correlated with dentin age using peak areas and absolute concentrations.

Main Results:

• Calibration plots showed good linearity (R > 0.98).
• D-Met met the criteria for an effective internal standard.
• Correlation coefficients of 0.98 (peak areas) and 0.90 (concentrations) were observed between dentin age and D-/L-Asp ratios.

Conclusions:

• The internal standard method, particularly with D-Met, offers reproducible and precise measurements for age estimation.
• Employing internal standards enhances quality assurance in age determination based on aspartic acid racemization.
• This approach helps mitigate potential errors in sample preparation and analysis.