背景:现场同时测定阴离子亚硝酸盐(NO2-)和硝酸盐(NO3-),和阳离子铵(NH4+),在工业和自然水域,提出了一个重大的分析挑战。为此,本文设计并优化了具有集成加热器芯片的3D打印微反应器,用于使用改进的Berthelot反应对NH4+进行柱后比色检测。该系统集成在便携式和现场可部署的离子色谱仪(Aquamonitrix)中,旨在分离和检测NO2-和NO3-,但是这里启用了双LED吸光度检测器,目的是提供第一个能够同时测定工业和天然水中阴离子和NH4的系统。
结果:结合了0.750mmI.D.3D打印的蛇纹石型微通道,用于样品-试剂混合和加热,所得微反应器的总反应器通道长度为1.26m,基于0.27mLmin-1的总流速,在40mm2的印刷面积内提供1.42min的反应时间。比色反应在微反应器内进行,然后将其耦合到专用的基于660nmLED的吸光度检测器。通过在短短40秒内快速提供70°C的反应器温度,达到了改善反应动力学的最佳条件,为NH4+提供0.1mgL-1的检测限,基于仅10μL的注射体积。在0-50mgL-1的范围内观察到NH4的线性,n=3,R2=0.9987。当作为Aquamonitrix分析仪中的柱后反应器时,发现该反应器具有出色的重现性,峰高的总体相对标准偏差低于1.2%,峰停留时间低于0.3%,基于6次重复注射。
结论:已将印刷的柱后反应器组件集成到为分离和检测NO2-和NO3-而开发的商业便携式离子色谱仪中,从而提供了一个完全自动化的系统,用于远程和同时分析NO2-,NO3-,以及天然和工业用水中的NH4+。全自动系统在温室设施的外部部署,以证明这种能力。
BACKGROUND: The on-site and simultaneous determination of anionic nitrite (NO2-) and nitrate (NO3-), and cationic ammonium (NH4+), in industrial and natural waters, presents a significant analytical challenge. Toward this end, herein a 3D-printed micro-reactor with an integrated heater chip was designed and optimised for the post-column colorimetric detection of NH4+ using a modified Berthelot reaction. The system was integrated within a portable and field deployable ion chromatograph (Aquamonitrix) designed to separate and detect NO2- and NO3-, but here enabled with dual LED-based absorbance detectors, with the aim to provide the first system capable of simultaneous determination of both anions and NH4+ in industrial and natural waters.
RESULTS: Incorporating a 0.750 mm I.D. 3D-printed serpentine-based microchannel for sample-reagent mixing and heating, the resultant micro-reactor had a total reactor channel length of 1.26 m, which provided for a reaction time of 1.42 min based upon a total flow rate of 0.27 mL min-1, within a 40 mm2 printed area. The colorimetric reaction was performed within the micro-reactor, which was then coupled to a dedicated 660 nm LED-based absorbance detector. By rapidly delivering a reactor temperature of 70 °C in just 40 s, the optimal conditions to improve reaction kinetics were achieved to provide for limits of detection of 0.1 mg L-1 for NH4+, based upon an injection volume of just 10 μL. Linearity for NH4+ was observed over the range 0-50 mg L-1, n = 3, R2 = 0.9987. The reactor was found to deliver excellent reproducibility when included as a post-column reactor within the Aquamonitrix analyser, with an overall relative standard deviation below 1.2 % for peak height and 0.3 % for peak residence time, based upon 6 repeat injections.
CONCLUSIONS: The printed post-column reactor assembly was integrated into a commercial portable ion chromatograph developed for the separation and detection of NO2- and NO3-, thus providing a fully automated system for the remote and simultaneous analysis of NO2-, NO3-, and NH4+ in natural and industrial waters. The fully automated system was deployed externally within a greenhouse facility to demonstrate this capability.