Microflow injection system based on a multicommutation technique for nitrite determination in wastewaters
Microflow injection system based on a multicommutation technique for nitrite determination in wastewaters
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DOI：
10.1039/b605043c
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发表时间：
2006-01-01
期刊：
影响因子：
4.2
通讯作者：
Alonso, Julian
中科院分区：
文献类型：
--
作者：
del Mar Baeza, Maria;Ibanez-Garcia, Nuria;Alonso, Julian
在这项工作中，将描述，评估和应用于实际样品的微流结构，适用于mu-FIA（微流注射分析）。微通道，检测器流池和输入/输出端口已经在硅中进行了微机械加工，并用阳极结合的耐热玻璃密封。这些通道是通过使用干反应离子蚀刻（RIE）工艺在硅中蚀刻大约200毫米深度来定义的。集成在芯片结构中的光学窗口允许进行简单的吸光度/透射测量。光学测量使用LED作为发射器（λ = 525 nm）和光电二极管作为检测器进行。开发了一个visual basic程序来控制自动滴管、三通电磁阀和数据采集系统。采用Griess-Ilosvay反应测定亚硝酸盐的mu-FIA方法对污水处理厂进行了在线监测。为了增强微系统内部的混合过程，应用了多重换相的概念。在不同的换向频率下，产生了试剂和样品的串联流并进行了评价。400/200 ms和150/450 ms两个最优频率是最合适的。第一个换相比产生了宽的线性工作范围（0 - 250 ppm），尽管高检测限（0.35 ppm）和低灵敏度（0.0041 +/- 0.0004 AU ppm(-1)）。使用第二种比例时，工作线性范围（0 ~ 50 ppm）较小，但检出限（0.17 ppm）和灵敏度（0.0091 +/- 0.0003 AU ppm(-1)）显著提高。最后，用所提出的mu-FIA系统分析了来自污水处理厂硝化过程动力学抑制研究的高亚硝酸盐浓度（0 - 1500ppm）的实际样品。所得结果较准确地证实了亚硝酸盐离子的抑制模型。
In this work a microflow structure, suitable for mu-FIA ( micro flow injection analysis), will be described, evaluated and applied to real samples. Microchannels, the detector flow cell and input/ output ports have been micromachined in silicon and sealed with anodically bonded Pyrex glass. The channels are defined by etching approximately 200 mm depth in silicon using a dry reactive ion etching (RIE) process. Optical windows integrated in the chip structure allow simple absorbance/transmission measurements to be made. The optical measurements were made using an LED as emitter (lambda = 525 nm) and a photodiode as a detector. A Visual-Basic program has been developed to control an automatic burette, three-way solenoid valves and the data acquisition system. The mu-FIA for nitrite determination using the Griess-Ilosvay reaction has been implemented for the on-line monitoring of wastewater treatment plants (WWTPs). The multicommutation concept has been applied in order to enhance the mixing process inside the microsystem. Tandem streams of reagent and sample were generated and evaluated at different commutation frequencies. Two optimal frequencies, 400/200 ms and 150/450 ms, were found to be the most suitable ones. The first commutation ratio gave rise to wide linear working range ( 0 - 250 ppm), in spite of a high detection limit (0.35 ppm) and a low sensitivity (0.0041 +/- 0.0004 AU ppm(-1)). With the second ratio, the working linear range was smaller ( 0 - 50 ppm) but the detection limit (0.17 ppm) and the sensitivity (0.0091 +/- 0.0003 AU ppm(-1)) improved remarkably. Finally, real samples with a high nitrite concentration ( 0 - 1500 ppm) coming from a study of kinetic inhibition in the nitrification process at a WWTP has been analysed with the proposed mu-FIA system. The obtained results have allowed the corroboration of the model of inhibition by the nitrite ion with great exactitude.