A method was developed to account for analytical losses of 14C-analyte when determining the concentration in biological samples using chromatographic separation and analysis by accelerator mass spectrometry. From the equations of J. Vogel and A.H. Love (in: A.L. Burlingame (Ed.), Methods in Enzymology, Academic Press, New York, 2005), new equations were derived to describe the isotopic dilution of a chromatographically isolated 14C-analyte. The analytical recovery for each sample was determined by the use of the UV response for nonlabeled analyte, as an internal standard against a standard curve. The slope of the curve was substituted into the equations to provide a method of accurately determining the analyte concentration. Â© 2008 Elsevier Inc. All rights reserved.