Detection of nucleotide bases in ancient seeds using gas chromatography/mass spectrometry and gas chromatography/mass spectrometry/mass spectrometry

Abstract

Nucleic acid extracts from 1400‐year‐old radish seeds recovered from excavations at Qasr Ibrim, Upper Egypt, have been analysed by gas chromatography/mass spectrometry and gas chromatography/mass spectrometry/mass spectrometry. tert‐Butyldimethyisilyl derivatives of the purine and pyrimidine bases were prepared, after treatment of the nucleic acid extracts with concentrated formic acid. Under electron ionization these derivatives yield prominent [M–57]+ ions that were found to be of value for use in analyses employing selected‐ion monitoring and product‐ion studies. These two techniques were used in the sensitive and selective detection of nucieotide bases in crude extracts of ancient seeds. The results obtained were supported by complementary analyses of hydrolysates of ancient nucleic acids and authentic bases by means of retention time and spectral comparisons. This work demonstrates for the first time that mass spectrometry can be used in the direct chemical examination of nucleotide bases in ancient materials. This analytical approach is currently being used to address questions regarding the possible chemical (diagenetic) changes occurring in the nucleic acids of ancient biological material.