Determination of ammonia in water by the Indophenol blue method catalyzed by manganese sulfate
Date Issued
2007
Date
2007
Author(s)
Lin, Ying-Chun
DOI
zh-TW
Abstract
The feasibility of using MnSO4 as a catalyst for the determination of ammonia in natural water based on the Indophenol blue reaction is studied. The salt interference on pH and color formation rate, the temperature effect on the kinetics of the formation reaction are examined in details. It was found that, using the MnSO4 catalyst, the reaction rate and the final molar extinction coefficient of the Indophenol blue complex are not affected by temperature but by the final pH, which is in oppose to the traditional Indophenol blue method using nitroprusside as a catalyzing agent. The maximum extinction coefficient of the freshwater samples is about 8000 M-1cm-1 at final pH=9.89 but it of the seawater samples is about 6600 M-1cm-1 at final pH=9.74. Samples of different salinities which would result in different final pH and different molar extinction coefficients. It is suggested the samples of different salinities should be added the same reagents to make the operation of determining ammonia in water easier. An empirical equation is nominated to correct for such salt error: Abs(corr.)=（Abs（actuality）-blank）× (0.4704×pH2 -9.935×pH +53.442)
Although the molar extinction coefficient by the proposed procedure is comparatively low, to be 7600 cm-1M-1, it takes advantage that the reaction time is much shorter (can be completed within 7 minutes under room temperature) than that of the traditional Indophenol blue method. The precision was 1 % at a concentration level of 20 mM, and the detection range is 0.5∼100 mM.
The rapid reaction time also render this method to be readily adopted by auto-analysis, thus becomes a useful tool for the study of ammonia in estuarine and coastal environment.
Subjects
靛藍法
靛藍呈色
測氨的方法
硫酸錳催化反應
自動分析
Indophenol blue reaction
color formation of Indophenol blue
determination of ammonia
the MnSO4 catalyst
auto-analysis
Type
thesis
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