Collagen proteins exchange O with demineralisation and gelatinisation reagents and also with atmospheric moisture.
Isabella C C von HolsteinMatthew von TerschAshley N CoutuKirsty E H PenkmanCheryl A MakarewiczMatthew J CollinsPublished in: Rapid communications in mass spectrometry : RCM (2018)
Studies of δ18 O values in collagen proteins should avoid extraction methods using acid solutions.