海水中硝酸盐的无阀连续流动分析

建立了一种无阀连续流动分析方法和装置,仅用一台多通道蠕动泵传送试剂和样品,无需依靠注入阀、电磁阀和定量环进行试剂或样品的选择和定量输入.样品通过铜-镉还原柱,将硝酸盐还原为亚硝酸盐,然后用重氮-偶氮光度法进行测定.研究结果表明,硝酸盐的线性范围为5 ～ 180 μmol/L,方法检出限为0.27.μmol/L,对10和80 μmol/L硝酸盐溶液连续测定11次,相对标准偏差分别为1.4％和1.3％,不同盐度的实际水样加标回收率在99.4％ ～ 106.1％之间.测定结果与流动注射分析法相比,无显著性差异.与流动注射分析相比,无阀设计装置大大降低了成本,操作更加简便,有利于在普通实验室或现场连续监测中推广使用.本方法成功应用于厦门西港海水样品中硝酸盐的测定以及九龙江河口区的硝酸盐走航式监测.

Determination of Nitrate in Seawater with Valve-free Continuous Flow Analysis

A valve-free continuous flow method and instrument were established,with only a multi-channel pump for delivering the sample and reagent,and without any injection or solenoid valves and sample loop for selecting and adding the sample or reagent.Nitrate was reduced to nitrite with Cu-Cd reductant column,and then detected with spectrophotometric detector.The proposed method was suitable for determination of nitrate at normal level in most of estuary and coastal seawaters.With the optimum parameters,the linear range and detection limit were 5-180 μmol/L and 0.27 μmol/L,respectively.The samples of 10 and 80 μmol/L nitrate were continually measured for 11 times,and the relative standard deviations were 1.4％ and 1.3％,respectively.The recovery of real samples at different salinity ranged between 99.4％ and 106.1％.There was no significant difference in the analytical results between the proposed method and the flow injection analysis (FIA).In comparison with FIA,the method and instrument were less cost and easy to operate,and was suitable to be applied in general laboratories and field for continuous monitoring.The method was successfully used to measure the nitrate in seawater samples in Xiamen's Western Harbor and monitor nitrate in Jiulongjiang estuary.