McCullagh's D.Phil. (Oxford) involved the development of a compound-specific radiocarbon dating method using preparative mixed-mode chromatography to separate individual amino acids derived from archaeological bone protein (mainly Type 1 collagen) which were then converted to carbon and then 14C content measured using accelerator mass spectrometry. This has become a gold-standard method for dating in archaeology as it provide collagen-specific dates with less interference from contamination associated that can be associated with other methods.
