The quantitative determination of metabolites of 6-mercaptopurine in biological materials. II. Advantages of a variable-wavelength HPLC spectrophotometric detector for the determination of 6-thiopurines.

The advantages of a variable-wavelength spectrophotometric detector for use in high-performance liquid chromatography are demonstrated with the detection of 6-mercaptopurine metabolites in cell extracts. 6-Methylthiopurines, unsubstituted 6-thiopurines and 6-thioguanines are most sensitively detected at 291, 322, and 342 NM, respectively. Compared with detection at 254 nm, the sensitivity at these wavelengths is about one to two orders of magnitude greater. Furthermore, in the 291-355-nm range, common purines, which are normally contained in cell extracts as free bases, nucleosides and nucleotides exhibit only minute absorbances and so do not interfere in quantitative determinations of 6-thiopurine compounds.