The L- and D-amino acid ratios are determined by gas and liquid chromatography..
The L-amino acids change to D-amino acids more or less steadily following death. As a result, remains of organisms that died long ago will have more D-amino acids than ones that died recently.
Aspartic acid (one of the 20 amino acids) is usually extracted from samples for this dating technique.
Dating is a technique used in archeology to ascertain the age of artifacts, fossils and other items considered to be valuable by archeologists.
There are many methods employed by these scientists, interested in the old, to get to know the age of items.
Before clay is fired and while lava is still in a molten state, the very weak magnetic fields of individual particles are randomly oriented. Later, its thermoremnant magnetism is measured with a magnetometer.