Analytical Sciences

Determination of Dissolved Silica in Seawater by Ion-exclusion Chromatography with Post-column Derivatization/Silicomolybdenum Yellow Detection

Chikako CHEONG, Yoshiyasu YAMAUCHI, and Tsutomu MIURA

National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan

The determination of dissolved silica in seawater was investigated by an ion-exclusion chromatography with a post-column derivatization/silicomolybdenum yellow method. To determine dissolved silica in seawater accurately, the experimental conditions, such as the volume of a reaction coil, the eluent concentration and the sample dilution factor, were optimized. This is the first report that has examined the details of the experimental condition for the measurement of dissolved silica in seawater by ion-exclusion chromatography with silicomolybdenum-yellow detection. The developed method was compared with the widely used continuous flow analysis and an ion-exclusion chromatography isotope dilution inductively coupled plasma mass spectrometry, which is a primary method of measurement. The analytical results by the three methods were in good agreement, considering the expanded uncertainty with a coverage factor, 2. The validity of the three methods was confirmed with each other. The developed method can give a quantitative value with less than 1% of the expanded uncertainty, and can be used for the determination of dissolved silica in candidate reference materials having a seawater matrix.

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