Measurement of WR-2721, WR-1065, and WR-33278 in plasma

Alkaline phosphatase was used in developing two new assays for WR-2721; one involved simple spectrophotometric titration with Ellman's reagent and the other was based upon HPLC analysis of a monobromobimane derivative. Both methods gave acceptable results when applied to whole plasma. Assays for WR-1065 and disulfide forms of the drug were also developed but were found to give unreliable results with whole plasma owing to apparent rapid reaction of these drug forms with plasma constituents. The methods were applied to the analysis of blood samples in rat 0-70 min after i.v. injection of WR-2721.