海水矽酸鹽測定方法中遮蔽劑之機制研究

Study of the Masking Reagents Used in the Determination of Silicate in Seawater

簡怡芳(Yi-Fang Chien)

指導教授 ： 白書禎

國立臺灣大學/理學院/海洋研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.01299

摘要

中文摘要

水體中的矽酸鹽目前常以矽鉬分光光度法測定之，過程中需要添加遮蔽劑阻止磷酸鹽的干擾。本論文使用自製恆溫循環流動迴圈之監測呈色反應裝置，對於不同種類的遮蔽劑作全面性的比較，遮蔽劑分別為草酸、酒石酸、檸檬酸和乙二胺四乙酸，探討方向為遮蔽劑反應作用機制、去除磷鉬黃干擾的效果與反應時間以及對於矽鉬黃褪色速率之影響程度。綜合實驗結果，本文建議選用檸檬酸作為遮蔽劑。在20℃室溫下進行手動測定，淡水樣品在加入檸檬酸40秒後開始測定並於5.5分鐘前完成，海水樣品在30秒到2.5分鐘內測定完畢；使用自動分析測定，溫度控制在40℃，海淡水樣品皆在添加檸檬酸15秒後即可流入光槽測量。

關鍵字

矽酸鹽測定 ； 遮蔽劑

並列摘要

Abstract

Silicate 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.

並列關鍵字

the determination of silicate ； masking agent

參考文獻

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