Sensitive determination of dissolved sulfide in estuarine water by solid-phase extraction and high-performance liquid chromatography of methylene blue

A sensitive method involving solid-phase extraction and HPLC analysis of me thylene blue has been developed to measure nanomolar levels of dissolved su lfide in oxic surface waters. The procedure included 1) a preconcentration step, in which methylene blue generated from sulfide reaction with n,n-dime thyl-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 minimiz e natural organic matter interference and detected by absorbance. The conce ntrations of the dissolved sulfide, quantified by standard addition, were a bout 2.1-4.7 nM in oxic surface waters from Galveston Bay, Texas. (C) 2000 Elsevier Science B.V. All rights reserved.