Determination of hydrogen sulfide in seawater using flow injection analysis and flow analysis1

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Abstract
Flow injection analysis (FIA) and flow analysis (FA) were used to automate the colorimetric determination of hydrogen sulfide by the methylene blue method. A low‐sensitivity FIA manifold for concentrations up to 200 µM H2S had a detection limit of 1.2 µM. A high‐sensitivity FIA manifold for concentrations up to 75 µM H2S had a detection limit of 0.12 µM. The C.V. was 10 M. Sulfide standards were calibrated by colorimetric measurement of the excess triiodide ion remaining after reacting sulfide with iodine. The FIA method was tested onboard ship with samples from the Galapagos hydrothermal vents and compared with results obtained in situ using FA.