Evaluation of a Ferrozine Based Autonomous in Situ Lab-on-Chip Analyzer for Dissolved Iron Species in Coastal Waters
Evaluation of a Ferrozine Based Autonomous in Situ Lab-on-Chip Analyzer for Dissolved Iron Species in Coastal Waters
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DOI：
10.3389/fmars.2017.00322
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发表时间：
2017-01-01
影响因子：
3.7
通讯作者：
Connelly, Douglas P.
中科院分区：
文献类型：
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作者：
Geissler, Felix;Achterberg, Eric P.;Connelly, Douglas P.
微量金属铁（Fe）是浮游植物生长和限制或共同限制世界大部分海洋表层初级生产的必需微量营养素。铁是一种氧化还原敏感元素，Fe（II）和Fe（III）共存于天然沃茨中。虽然Fe（II）是最可溶的形式，但它也是短暂的，在含氧海水中具有快速氧化速率。因此，Fe（II）的测量优选在原位进行。为此目的，自主湿化学分析仪的芯片上的实验室技术的基础上，开发的溶解（< 0.45 μ m）的Fe物种（Fe（II）和不稳定的Fe）的浓度适合在广泛的水生环境中部署的原位测定。分光光度法利用缓冲亚铁锌溶液和亚铁锌/抗坏血酸混合物的Fe（II）和不稳定的Fe（III）的分析，分别。扩散混合、显色和分光光度检测在三个不同长度的单独流动池中进行，使得分析仪可以根据所需的应用测量从低nM到几nM的Fe的宽浓度范围。作为SenseOCEAN欧盟项目的一部分，该微流控分析仪与其他传感器一起在德国基尔峡湾的沃茨中进行了为期9天的原位测试。使用根据GEOTRACES方案收集和处理的离散样品[酸化至pH < 2并通过电感耦合等离子体质谱法（ICP-MS）分析]评估分析仪在自然条件下的性能。分析仪在9天内的机械性能良好（Fe（II）和Fe（III）标准品的一致高精度，标准偏差分别为2.7%（n = 214）和1.9%（n = 217），并且成功完成每个编程数据点）。然而，与ICP-MS数据相比，总溶解铁始终较低。回收率在16%和75%之间，这表明该分析仪不能测量沿海海水中天然溶解的Fe物质的显著部分。建议酸化步骤是必要的，以确保分析仪得出的总溶解铁浓度是可重现的，并与离散值一致。
The trace metal iron (Fe) is an essential micronutrient for phytoplankton growth and limits, or co-limits primary production across much of the world's surface ocean. Iron is a redox sensitive element, with Fe(II) and Fe(III) co-existing in natural waters. Whilst Fe(II) is the most soluble form, it is also transient with rapid oxidation rates in oxic seawater. Measurements of Fe(II) are therefore preferably undertaken in situ. For this purpose an autonomous wet chemical analyzer based on lab-on-chip technology was developed for the in situ determination of the concentration of dissolved (< 0.45 mu m) Fe species (Fe(II) and labile Fe) suitable for deployments in a wide range of aquatic environments. The spectrophotometric approach utilizes a buffered ferrozine solution and a ferrozine/ascorbic acid mixture for Fe(II) and labile Fe(III) analyses, respectively. Diffusive mixing, color development and spectrophotometric detection take place in three separate flow cells with different lengths such that the analyzer can measure a broad concentration range from low nM to several it M of Fe, depending on the desired application. A detection limit of 1.9 nM Fe was found. The microfluidic analyzer was tested in situ for nine days in shallow waters in the Kiel Fjord (Germany) along with other sensors as a part of the SenseOCEAN EU-project. The analyzer's performance under natural conditions was assessed with discrete samples collected and processed according to GEOTRACES protocol [acidified to pH < 2 and analyzed via inductively coupled plasma mass spectrometry (ICP-MS)]. The mechanical performance of the analyzer over the nine day period was good (consistent high precision of Fe(II) and Fe(III) standards with a standard deviation of 2.7% (n = 214) and 1.9% (n = 217), respectively, and successful completion of every programmed data point). However, total dissolved Fe was consistently low compared to ICP-MS data. Recoveries between 16 and 75% were observed, indicating that the analyzer does not measure a significant fraction of natural dissolved Fe species in coastal seawater. It is suggested that an acidification step would be necessary in order to ensure that the analyzer derived total dissolved Fe concentration is reproducible and consistent with discrete values.