Plasma
dryness
Two pooled plasma samples from TP2 were prepared from the six human subjects based on total radioactivity in the samples. A primary pool comprising approximately 95% of the total plasma radioactivity was created according to the area under the response‐time curve (AUC) concentration‐time proportional pooling method.The two plasma pools were subjected to protein precipitation cleanup in three serial steps of methanol/acetonitrile extraction and centrifugation. Resultant supernatants were combined and evaporated to near dryness under a stream of nitrogen. Remaining residues were reconstituted in methanol/water (1:4) at a concentration factor of 5. Radioactivity recovery and concentration following sample cleanup was determined by LSC prior to subsequent quantitative radio‐HPLC analysis.