A five-parameter in situ seawater nutrients analyzer was developed based on wet chemical reaction principle, combined the spectrophotometric method with flow injection analysis technology. A loop flow was controlled by peristaltic pump and three-way valve in this analyzer, which has the advantages of small size, high-stability, lowreagent consumption and high automation. The linear range, detection limit, accuracy and precision of the instrument were verified through the experiment. The detection linear ranges for nitrite, nitrate, ammonium, phosphate and silicate were 5~250, 10~500, 10~500, 10~300 and 10~1 000 μg/L, respectively. The minimum detection limits for nitrite, nitrate, ammonium, phosphate and silicate were 0.81, 3.01, 1.79, 2.54 and 3.02 μg/L, respectively. The relative standard deviations (RSD) for nitrite, ammonium and silicate were less than 3% and the relative standard deviations (RSD) for nitrate and phosphate were less than 5%. The on-site comparison tests between the developed nutrients analyzer and the national standard methods were finished, and the results were basically the same, which indicated that the analyzer was entirely feasible and could reflect the content and changes of the nutrients in the seawater. The nutrients analyzer can be loaded on vessel, stations, buoy platform, and also can be used in the laboratory.
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