caa a22 4500 605455147 CHVBK 20210128100210.0 cr unu---uuuuu 210128e20150201xx s 000 0 eng 10.1007/s10872-014-0260-6 doi (NATIONALLICENCE)springer-10.1007/s10872-014-0260-6 A highly sensitive and large concentration range colorimetric continuous flow analysis for ammonium concentration [Elektronische Daten] [Taketoshi Kodama, Tadafumi Ichikawa, Kiyotaka Hidaka, Ken Furuya] A continuous flow method for the determination of ammonium concentration in seawater from a nanomolar to a micromolar level is described. To prevent spurious peaks derived from salinity difference, a gas-permeable hydrophobic membrane filter was used to separate the manifold into an outgassing section and an indophenol blue reaction section. The indophenol blue reaction section was adopted for colorimetric analysis and is equipped with a 1-m path length liquid capillary cell and a fiber-optic spectrometer, which is able to record the absorbance at multiple wavelengths. The minimum detection limit at wavelength 630nm is 5.5±1.8nM, and the calibration curves are linear to at least 2,000nM. In addition, the minimum detection limit at wavelength 530nm was 13±5.3nM, and linear calibration curves were observed until at least 10,000nM. The slopes of the calibration curves were similar for standards prepared using filtered seawater and ultrapure water. The ammonium concentration of the ultrapure water was similar to those of ion-exchanged water and unfiltered low-nutrient seawater, but was significantly lower than those of filtered seawater and solutions that contained sodium hydroxide. Therefore, ultrapure water is optimal for both blank and standard preparations because of its stable quality and availability. Given its large concentration range and the use of readily available blanks, this method is suitable for the determination of ammonium concentration and helps our understanding of ammonium dynamics in the ocean. The Oceanographic Society of Japan and Springer Japan, 2014 Ammonia nationallicence Ammonium ion nationallicence Nanomolar level nationallicence Liquid waveguide capillary cell nationallicence Salt effect nationallicence Highly sensitive nationallicence Nitrogen dynamics nationallicence Autoanalyzer nationallicence Kodama Taketoshi National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, 236-8648, Yokohama, Kanagawa, Japan aut Ichikawa Tadafumi National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, 236-8648, Yokohama, Kanagawa, Japan aut Hidaka Kiyotaka National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, 236-8648, Yokohama, Kanagawa, Japan aut Furuya Ken Department of Aquatic Bioscience, The University of Tokyo, Yayoi, 113-8657, Bunkyo, Tokyo, Japan aut Journal of Oceanography Springer Japan 71/1(2015-02-01), 65-75 0916-8370 71:1<65 2015 71 10872 https://doi.org/10.1007/s10872-014-0260-6 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10872-014-0260-6 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kodama Taketoshi National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, 236-8648, Yokohama, Kanagawa, Japan aut NATIONALLICENCE 700 1- Ichikawa Tadafumi National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, 236-8648, Yokohama, Kanagawa, Japan aut NATIONALLICENCE 700 1- Hidaka Kiyotaka National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, 236-8648, Yokohama, Kanagawa, Japan aut NATIONALLICENCE 700 1- Furuya Ken Department of Aquatic Bioscience, The University of Tokyo, Yayoi, 113-8657, Bunkyo, Tokyo, Japan aut NATIONALLICENCE 773 0- Journal of Oceanography Springer Japan 71/1(2015-02-01), 65-75 0916-8370 71:1<65 2015 71 10872