基于程控注射泵耦合镉-铜还原柱半自动测定海水硝酸盐的方法改进

Improvement of method for semi-automatic determination of nitrate in seawater basedon program-controlled injection pump coupled with cadmium-copper reduction column

镉-铜还原法是用于测定海水中硝酸盐含量最广泛的方法,也是我国海洋监测规范中推荐的传统标准方法,但该方法目前存在需要人工值守避免镉柱过空、流速控制较难等问题。本研究在镉-铜还原柱末端引入了程控注射泵,有效避免了过空镉柱的可能性,实现了5~20 mL/min的流速精确控制。将新装置与传统装置对标准溶液的测定结果进行了对比,改进后的装置具有更低的相对标准偏差(0.4%)和过柱时间(5.0 min),并具有更低的检出限(0.05μmol/L)。结果表明,改进后的装置具有更优的精密度、准确度以及更高的效率。此外,对青岛近海的海水样品进行改进前后的对比测定,结果表明两种装置的测定结果不存在显著性差异,且具有良好的一致性。因此,加装程控注射泵为镉-铜还原法带来了更加精密、便捷的操作体验,适合在海洋监测一线部门进行推广普及。

The cadmium-copper reduction method is widely utilized for determining the nitrate content in seawater,and it is also the recommended standard method in China’s marine monitoring specifications.However,this method currently requires manual monitoring to prevent over-emptying of the cadmium column,and have difficulties in flow rate control,while other issues also existing.In this study,we introduce a program-controlled syringe pump at the end of the cadmium-copper reduction column.This innovation effectively eliminates the possibility of over-emptying the cadmium column and enables precise flow rate control ranging from 5-20 mL/min.To evaluate the performance of the new device,we compared its results with the conventional device for determining standard solutions.The improved deviceexhibited lower relative standard deviation(0.4%),and the time to pass the column(5.0 min).Additionally,it demonstrated a lower detection limit of 0.05μmol/L.These indicate that the improveddevice has superior precision,accuracy,and higher efficiency.Furthermore,we conducted a comparisonbefore and after the improvement using seawater samples from the Qingdao coastal area.The resultsshowed no significant differences,demonstrating good consistency.Therefore,the incorporation of aprogrammed syringe pump brings about a more precise and convenient operation for the Cd-Cu reductionmethod,rendering it suitable for widespread use in front-line marine monitoring units.