Dowling, Geraldine and Regan, L (2011) A new mixed mode solid phase extraction strategy for opioids, cocaines, amphetamines and adulterants in human blood with hybrid liquid chromatography tandem mass spectrometry detection. Journal of Pharmaceutical and Biomedical Analysis, 54, (5), pp. 1136-1145. https://doi.org/10.1016/j.jpba.2010.11.043.