this might be useful

McCullagh, J.S.O., Tripp, J.A. & Hedges, R.E.M., (2005), Carbon isotope
analysis of bulk keratin and single amino acids from British and North
American hair, Rapid Communications in Mass Spectrometry, 19(22),3227-3231.

Julie Hamilton
Research Laboratory for Archaeology and the History of Art
Dyson Perrins Building
South Parks Rd
OXFORD OX1 3QY

email: [log in to unmask]
Tel: (01865 ) 285203