pH and buffering capacity problems involved in the determination of ammonia in saline water using the indophenol blue spectrophotometric method

被引：184

作者：

Pai, SC ^{[1
]}

Tsau, YJ ^{[1
]}

Yang, TI ^{[1
]}

机构：

[1] Natl Taiwan Univ, Inst Oceanog, Taipei 10764, Taiwan

来源：

ANALYTICA CHIMICA ACTA | 2001年 / 434卷 / 02期

关键词：

ammonia; indophenol blue; pH; buffering capacity;

D O I：

10.1016/S0003-2670(01)00851-0

中图分类号：

O65 [分析化学];

学科分类号：

070302 ; 081704 ;

摘要：

Magnesium ions in brackish water or sea water complex with the citrate reagent (CIT) and thus interfere with the indophenol blue spectrophotometric method for ammonia measurement by altering the final pH of the color solution. The complex system, possibly Mg(CIT)(-) + OH- double left right arrow Mg(OH)(CIT)(2-), shows buffer characteristics and can be identified by acid-base titration. A maximum capacity of ca. 40 mu eq pH(-1) ml(-1) was found at pH 10.2 when [Mg2+] was 0.045 M. To compensate for this capacity. extra alkali reagent should be added to sea water samples for the optimal IPB color reaction. For samples with a wide salinity range, the results still need to be corrected empirically either for pH. [Mg2+] or salinity. (C) 2001 Elsevier Science B.V. All rights reserved.

引用

页码：209 / 216

页数：8

共 12 条

[1] Determination of ammonia in seawater by the indophenol-blue method: Evaluation of the ICES NUTS I/C 5 questionnaire [J].