Study of the Masking Reagents Used in the Determination of Silicate in Seawater
Date Issued
2008
Date
2008
Author(s)
Chien, Yi-Fang
Abstract
Abstractilicate in natural water is usually determined colorimetrically by reacting with molybdate reagent. A further treatment using masking agent is necessary to eliminate the interference of phosphate. This study focuses on the mechanism of the masking reagents. Four reagents were chosen namely oxalic acid, tartaric acid, citric acid and EDTA, and their effects to the silicate determination were monitored by a thermostatic closed circulating device. It was found that different reagents could cause fading of silicomolybdic complex, and that citric acid provides the least fading rate and minimum required dose. In manual operation freshwater samples should be measured with in 40 s and 5.5 min after mixing with citric acid reagent, whereas for seawater sample the optimal measuring time is between 30 s and 2.5 min at room temperature. For flow injection analysis when a heating bath at 40 ℃ is applied the yellow color stream should be lead to a detecting device, within 15 s after meeting the reagent flow, for prompt measurement.
Subjects
the determination of silicate
masking agent
Type
thesis
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