Measurement of nano molar ammonium with a cyclic olefin copolymer microchip and low-power LED
Measurement of nano molar ammonium with a cyclic olefin copolymer microchip and low-power LED
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DOI：
10.1016/j.sbsr.2023.100611
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发表时间：
2023-12-05
影响因子：
5.3
通讯作者：
Mowlem，Matthew C.
中科院分区：
文献类型：
--
作者：
Bey，Samer K. Abi Kaed;Mowlem，Matthew C.
在贫营养区，铵（NH 4+）浓度可能低于50 nM，然而，很少有现有的仪器可以测量低于这个水平的高置信度。这项工作，邻苯二甲醛（OPA）荧光分析的基础上，适用于测量纳摩尔NH 4+在一种新的光流体环烯烃共聚物（COC）微芯片使用低功率（20 mW）发光二极管（LED）作为激发源。首先使用光线跟踪软件对光学布置进行建模，以确定初始检测体积尺寸。用5 nM至1000 nM的人工海水制备的铵标准品一式三份运行。当考虑校准曲线上各测定浓度的y轴截距和垂直变化时，所得检测限（LOD）为1.5 nM（空白的3 x σ）或LOD为15 nM（y轴截距+3. Sy/x）。5 nM和1000 nM的精密度分别为3.3%和0.5%。还使用五种不同的标准浓度将光流体系统与现成的荧光计（Jasco FP 2020）和现有的高分辨率船载分析仪进行了比较。Jasco FP 2020、船载分析仪和当前微系统的LOD和铵浓度不确定度分别为217 nM、39 nM和15 nM以及± 232 nM、± 48 nM和± 16 nM。还使用来自大西洋的真实的样本验证了光学设置。这种光学设计，没有光纤，使系统简单，适合与其他荧光检测时，紧凑，坚固，低成本，低功耗仪器是必需的。
In oligotrophic regions, ammonium (NH4+) concentrations can be below 50 nM, however, few existing instruments can measure below this level with high confidence. This work, based on the o-pthaldialdehyde (OPA) fluorescence assay, is applied to measure nanomolar NH4+in a novel optofluidic Cyclic Olefin Copolymer (COC) microchip using a low-power (20 mW) Light Emitting Diode (LED) as the excitation source. The optical arrangement was first modeled using ray tracing software to determine the initial detection volume size. Ammonium standards made with artificial seawater of 5 nM to 1000 nM, were run in triplicates. The limit of detection (LOD) obtained was 1.5 nM (3 x σ of the blank) or a LOD of 15 nM when the y-intercept and the vertical variation of each measured concentration on the calibration curve were taken into consideration (y-intercept +3. Sy/x). Precision at 5 nM and 1000 nM was 3.3% and 0.5% respectively. The optofluidic system was also compared to an off-the-shelf fluorometer (Jasco FP2020) and an existing high-resolution shipboard analyser using five different standard concentrations. The LOD and the ammonium concentrations uncertainty for the Jasco FP2020, shipboard analyser, and current microsystem were 217 nM, 39 nM, and 15 nM and ± 232 nM, ± 48 nM, and ± 16 nM respectively. The optical setup was also validated using real samples from the Atlantic. This optical design, without optical fibres, makes the system simple and suitable for use with other fluorescent assays when compact, rugged, low-cost, and low-power consumption instrumentation is required.