Tang DGSantschi PHJournal of Chromatography A2010-02-152010-02-152000 Jun 2http://hdl.handle.net/1969.3/23456305-309A sensitive method involving solid-phase extraction and HPLC analysis of methylene blue has been developed to measure nanomolar levels of dissolved sulfide in oxic surface waters. The procedure included 1) a preconcentration step, in which methylene blue generated from sulfide reaction with n,n-dimethyl-p-phenylenediamine in acidic conditions in the presence of ferric ion was absorbed onto Waters tC(18) cartridge; and 2) a determination step, in which methylene blue was separated by HPLC in a gradient elution to minimize natural organic matter interference and detected by absorbance. The concentrations of the dissolved sulfide, quantified by standard addition, were about 2.1-4.7 nM in oxic surface waters from Galveston Bay, Texas. (C) 2000 Elsevier Science B.V. All rights reservedwater analysismethylene bluesulfideSEAWATERJournal