铵氮不同分析方法的对比

A contrast on various determination methods of ammonium

铵氮（NH4-N）一直是海洋观测项目中的重要指标。目前海水中NH4-N的测定方法主要有次溴酸钠氧化法、靛酚蓝法以及荧光法。论文完善了荧光法的实验条件，最佳反应温度为25℃，反应时间在0．5～72h内，样品与试剂的体积比可以灵活选择。探讨了三种方法的基体效应，结果表明靛酚蓝法与荧光法存在基体效应，需要标准加入法进行校正。对比了海水样品的保存方法，HgCl2会造成荧光猝灭，CHCl3不适宜用于保存海水样品，冷冻法均适用于三种NH4-N测定方法。用三种方法同时测定黄、东海海水中NH4-N含量，靛酚蓝法与荧光法的测量结果较接近，次溴酸钠氧化法测定结果比靛酚蓝法和荧光法的测定结果平均高出27％，而在NH4-N浓度小于1μmol／L时则会高出60％，这是因为次溴酸钠氧化法的测定结果中包含一定浓度的氨基酸。

Ammonium has been an important parameter in marine investigations. The main determination methods of ammonium in sea water were sodium hypobromite oxidation, indophenol blue and fluorimetric methods. This study further improved the measurement conditions of fluorimetric method, optimum temperature was 25℃, reaction time was in 0.5 - 72 h, volume ratio of water and reagent could change freely. Matrix effects of these three methods were discussed,indophenol blue and fluorimetric method had matrix effect, so standard addition method was used for calibration. Preservation methods of sea water were also discussed, HgCl2 could cause fluorescence quenching, CHCl3 was not appropriate for preservation of seawater, frozen method was optimum. Ammonium in seawater sampies of the East China Sea and the Yellow Sea were determined with these three methods, the results showed that indophenols blue method and fluofimetric method gave similar values, while the results of sodium hypobromite oxidation method were averagely 27% higher than the other two methods,but when the ammonium concentration was less than 1 μmol/L, they would 60% higher, because the results of sodium hypobromite oxidation method contained some of amino acids.