The following text discusses problems encountered during analysis for tributyltin (TBT). It is specific to analytical procedures that use extraction with an organic solvent (i.e., hexane, toluene, or methylene chloride), derivatization with a Grignard reagent, and gas chromatograph detection using either flame photometric or mass spectrometric detection (See Figure 1). Similar difficulties may be encountered using other procedures (i.e., hydride derivatization/graphite furnace), but these issues relate specifically to the procedure mentioned above, which is used on the U.S. EPA-required environmental monitoring program. Figure 1 presents a schematic of a typical analytical procedure.