M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)
Dating - CSAPÓ János, KÖLTŐ László , PAP Ildikó: Archaeological age determination based on the racemization and epimerization of amino acids
to the factors affecting the racemization (heavy metal ions, the presence orlackofCa 24 and Mg 2+ ions, pH, ionic strength ). The protein fraction seems to be better for this purpose. During the hydrolysis of the protein fraction special attention has to be paid to avoiding all those side effects which may change the amino acids during the process of hydrolysis (oxidation, reduction, racemization, epimerization). To check the changes occurring during the preparational stages analysis of a contemporary pig bone should be performed,and the changes occurring here must be taken into account (racemization, epimerization during the hydrolysis) when determining the age of the sample. The determination of isoleucine and D-alloisoleucine as described under section 4. are conducted on a routine basis. The reliability of age determination is ±3% for isoleucine and ±5 r ' for D-alloisoleucine.. The disadvantage of the method is that isoleucine belongs to the group of amino acids with a long epimerizational half-time, therefore an exact result can be excepted only for those samples whose age is over 50 000 years. Between 20 000 and 50 000 years the analytical error of the method for D-alloisoleucine increases. It may even reach the 15-20% margin. For samples younger than 20000 years, the traces of D-alloisoleucine cannot be (exactly) determined, therefore the method cannot be applied in this range. Amino acids with fast racemization belonging to the first group can favourably be used for the range 5000 to 20000 years, as the D and L version can be determined by a chiral silica gel following ion-exchange column-chromatographic separation. As the evaluation is conducted with a densitometer, the error of analytical determination reaches 15-20% in this range. This error can, however be reduced to 1—3%, if we succeed in the simultaneous separation of D- and L-amino acids and their determination by high pressure liquid chromatography. At the present stage of our work it is anticipated that this problem will have been solved in some months. To summarize it can be stated that we are able to determine the ages of samples over 50000 years with D-alloisoleucine and with isoleucine, with amino acids having a fast racemization time the ages between 5000 and 50 000 can be determined,or estimated with the stated accuracy. Even amino acids with fast racemizational time are "slow enough" to be utilized to determine ages between 500 and 2000 years. Therefore the question arises concerning which of the amino acids or some other components could be used in this range, or how could a solution be found for this range. An obvious possibility is the application of amino acids containing sulphur, which are sensitive to oxidation, i. e. the methionine and the cystine. Cystine and cysteine are changed to cystein-sulphin acid by oxidation, and intocysteicacid by further oxidation, while methionine is transformed into methionine-sulphoxide and later into methionine-sulphon. For both amino acids the different forms of oxidation can easily be measured by ion-exchange column-chromatography, therefore there is no problem is checking the process of oxidation. It can be assumed that for samples originating from similar conditions a correlation can be established between the age and the different forms of oxidational states. For samples of the same age we have tried to determine the fatty acid, and to establish some correlation between the age and their amount. We plan to deal with the gas-chromatographic fatty acid determination and its evaluation in a future article.
