A Submersible Flow-through Analyzer for in situ Colorimetric Measurement down to 2000 m Depth in the Ocean

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Abstract
We developed a flow-through chemical analyzer usable in seawater up to a depth of 2000m. The analyzer, which can measure silicate and hydrogen sulfide dissolved in seawater, consists of the following four parts: (i) an acrylic oil-filled vessel containing the flow-through analyzer, (ii) a pressure housing containing electronic circuits (CPU, data logger and drivers to control the analyzer), (iii) a bundle of plastic bags keeping analytical reagents and waste solutions and (iv) batteries for powder supply. Si and H2S are determined colorimetrically using the Molybdenum Blue method and the Methylene Blue method, respectively. After the test operation up to a pressure of 2×107 Pa in a shore-based laboratory, the system was submerged in seawater down to 1200m depth to perform successful in situ Si measurements.