Estimation of ages from racemization of an amino acid in teeth--assessment of errors under various experimental conditions.

In order to estimate ages of corpses more accurately from racemization of an amino acid (aspartic acid) in the dentine of teeth, errors resulting from various experimental conditions were assessed. The factors included for evaluation were: the sample weight, time and temperature of hydrolysis, concentration of hydrochloric acid, and the volume of the hydrochloric acid solution, each of which might have effect on resulting errors. This study revealed that alteration of the sample weight did not change the D/L ratio and that the estimated age remained constant as long as the sample weight was within the range of 3 mg and 50 mg. However, with the remaining factors, the D/L ratio changed with the alteration of conditions. The correlation can be represented by a straight line in a graph, which is a sign of the first order reaction. The coefficients of correlation were between 0.972 and 0.999, indicating their extremely high correlation with the D/L ratio. The errors expressed in estimated age values per unit of variables were: 0.02 years/min. for a time (min.) of hydrolysis; 1.5 years/degrees C for temperature of hydrolysis; 0.5 years/0.1 N (normal) for concentration of hydrochloric acid; and 0.6 years/ml for the volume of hydrochloric acid solution. Consequently, the temperature of hydrolysis was found the most influential. Alteration of values of the other four factors did not largely affect the estimation.