The ratio of the D and L enantiomers of aspartic acid can be used to estimate the age of human remains. The teeth show a relatively low metabolic turnover during life and tend to be well preserved after death. Collagen extracted from dentin can be used as a source of amino acids that can be analyzed by chromatography.



(1) Primary dentin is chipped from the dentino-enamel junction using a diamond disk cooled with water. The pieces are powdered using a vibratory mill.

(2) The dentin is then demineralized with 0.5 M sodium EDTA adjusted to pH 7.4.

(3) The dentin is hydrolyzed with 6 M hydrochloric acid at 100°C for 6 hours.

(4) Amino acids are derivatized into isopropyl esthers using isopropanol and acetyl chloride. This is then derivatized with trifluoroacetic acid anhydride.

(5) The sample is then injected into a GC or HPLC. The signal is reported in mV and the elapsed time in minutes.


ratio of D-asparatic acid to L-aspartic acid =

= (area of peak for D-aspartic acid) / (area of peak for L-aspartic acid)


coefficient of racemization = KR =

= LN ((1 + (ratio of the enantiomers)) / (1 - (ratio of the enantiomers)))


Regression equation 1 (page 1230) for 71 persons between the ages of 15 and 95 (R = 0.93):


age of the patient in years =

= ((coefficient of racemization) – 0.0352) / 0.0006 =

= 1666.67 * ((coefficient of racemization) – 0.0352)


Regression equation 2 (page 1230) for 46 persons between the ages of 15 and 60 (R = 0.96):


age of the patient in years =

= ((coefficient of racemization) – 0.02269) / 0.0009 =

= 1111.11 * ((coefficient of racemization) – 0.02269)



• The estimate is considered reliable provided the preparation and analysis are conducted precisely. Inaccuracies at any step in the process can affect the result.


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