Abstract：The spectroscopic detection of ammonium (NH+4) has great significance. With the development of microfluidics, microfluidic spectroscopic analysis aiming at rapid, portable and multi-component detection has realized tremendous achievements. However, the excessive consumption of the indicating material which exists all the time has not been settled yet. Zinc porphyrin, being a natural chromophore, can reversibly detect NH+4 and settle the problem. But it suffers from the lack of selectivity. In allusion to these issues, a coupled microfluidic chip which consists of a reaction chip, a gas-diffusion chip and a detection chip is fabricated in our experiments. The reaction chip made of polydimethylsiloxane can convert NH+4 into NH3. The gas-diffusion chip which is made of two glass chips and a piece of polydimethylsiloxane gas-diffusion membrane allows NH3 diffuses into the detection solution. The detection chip immobilizes the indicating material tightly through the multi-layer structure. The indicating material fabricated by dying zinc porphyrin on the surface of the cation exchange resin permanently will turn from green to purple when it meets NH3 and will turn reversely into green when pure water is around. Using the coupled chip as the analytical platform, we set up a miniaturized spectroscopic detection system. With a portable spectrometer being the analytical instrument, we detect NH+4 by the transmission spectrum intensity change at the wavelength of 450 nm and study three factors that could affect the detection performance: the thickness of the gas-diffusion membrane, the flow rate and the dosage of the indicating material. First, we confirm the reversibility of the indicating process and settle the issue of indicating material consumption by the spectrum change intensity. The time responses show the rapidity of the indicating process. Then through the comparison to the contrast experiment, the high selectivity of the indicating process is demonstrated because the interference has no influence and the spectrum change is attributed merely to NH3. The relationship between the membrane thickness and the spectrum intensity change is obtained by changing the thickness of the gas-diffusion membrane in the gas-diffusion chip. Results show that the increase of the membrane thickness leads to a worse detection performance, but the outcome remains stable when the thickness is less than 10 μm. So 10 μm is selected as the optimal thickness in consideration of the mechanical strength. The impact of the flow rate is investigated afterwards. The results exhibit that the increase of the flow rate will decrease the spectrum intensity change, but the performance becomes unchanged when flow rate is less than 5 μL·min-1. Last, how the dosage of the indicating material impacts the results is studied. It is demonstrated that both excessive and inadequate indicating material will deteriorate the performance. So 5 mg is selected as the optimal amount. The spectroscopic detection system which uses the coupled chip as the analytical platform has the advantages of small volume, high economy, rapid response and realizes highly selective and reversible NH+4 detection.
周 昊，杨 正. 基于耦合微流控芯片的可逆式铵检测及其影响因素研究[J]. 光谱学与光谱分析, 2019, 39(12): 3749-3754.
ZHOU Hao, YANG Zheng. The Reversible Ammonium Detection Based on the Coupled Microfluidic Chipand the Investigation of the Impact Factors. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(12): 3749-3754.
[1] Muzio L, Bogseth S, Himes R, et al. Fuel, 2017, 206: 180.
[2] HJ 535—2009, Water Quality—Determination of Ammonia Nitrogen—Nessler’s Reagent Spectrophotometry(水质氨氮的测定纳氏试剂分光光度法).
[3] HJ 536—2009, Water Quality—Determination of Ammonia Nitrogen—Salicylic Acid Spectrophotometry(水质氨氮的测定水杨酸分光光度法).
[4] GU Wen-wen(顾雯雯). Optics and Precision Engineering(光学精密工程), 2014, 22(8): 2159.
[5] ZHANG Hao, GONG Li, XIE Fang-yan, et al(张 浩，龚 力，谢方艳，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2017, 37(2): 350.
[6] YANG Xing-hua, YUAN Ting-ting, ZHAO Qi-kai, et al(杨兴华，苑婷婷，赵其锴，等). Journal of Applied Sciences(应用科学学报), 2017, 35(4): 503.
[7] LIU Jun-shan, XIAO Qing-long, GE Dan, et al(刘军山，肖庆龙，葛 丹，等). Chinese Journal of Analytical Chemistry(分析化学), 2015, 43(7): 977.
[8] MU Li-li, RONG Li, HUANG You-rui, et al(穆莉莉，荣 莉，黄友锐，等). Micronanoelectronic Technology(微纳电子技术), 2016, 53(2): 108.
[9] ZHANG Ya-ting, ZHANG Yan, ZHANG Yi, et al(张雅婷，张 炎，张 毅，等). Chinese Journal of Analysis Laboratory(分析试验室), 2018, 37(1): 7.
[10] Xu H, Zhang M C, Ding H B, et al. MicrochimicaActa, 2013, 180: 85.
[11] HE Jie, LUO Wei-feng, SONG Xue-yan, et al(何 洁，罗伟丰，宋雪妍，等). Chemistry(化学通报), 2013, 76(2): 179.
[12] Peter C, Schmitt K, Apitz M, et al. Microsystem Technologies, 2012, 18: 925.
[13] Li X R, Wang B, Xu J J, et al. Electroanalysis, 2011, 23: 2955.
[14] ZHANG Lu, QUAN Hong-hua, YANG Kai, et al(张 路，全红花，杨 凯，等). Physical Testing and Chemical Analysis (Part B: Chem. Anal.)(理化检验-化学分册), 2018, 54(7): 831.
[15] Zilberman Y, Chen Y, Sonkusale S R. Sensors and Actuators B，2014, 202: 976.
[16] LAN Ying, XU Juan, BIAN Xiao-jun, et al(蓝 英，徐 娟，卞晓军，等). Journal of Instrumental Analysis(分析测试学报), 2016, 35(6): 635.
[17] Song Y L, Shi Y Z, Li X R, et al. Analytical Chemistry, 2016, 88: 8294.
