Physical Sciences Department, MacEwan University, 10700-104 Avenue, Edmonton, AB, T5J 4S2, Canada.
Department of Decision Sciences, MacEwan University, 10700-104 Ave, Edmonton, Canada.
Mikrochim Acta. 2022 Apr 30;189(5):206. doi: 10.1007/s00604-022-05307-4.
Concerns for agri-food safety and environmental management require development of simple to use and cost- and time-effective multiplex sensors for point-of-need (PON) chemical analytics by public end-user. Simultaneous detection of nitrates, phosphates, and pH is of importance in soil and water analysis, agriculture, and food quality assessment. This article demonstrates a suite of stainless steel microneedle electrochemical sensors for multiplexed measurement of pH, nitrate, and phosphate using faradaic capacitance derived from cyclic voltammetry as the mode of detection. The multi-target microneedle sensors were fabricated by layer-by-layer (LbL) assembly in a stainless steel hypodermic microneedle substrate. For nitrate sensing, the stainless steel was coated with carbon nanotube/cellulose nanocrystal (CNT)/CNC) decorated with silver nanoparticles (Ag). For pH measurement, the polyaniline (pANI) was coated onto the CNT/CNC@Ag film, while for phosphate detection, the CNT/CNC/Ag @pANI microneedle was further decorated with ammonium molybdenum tetrahydrate (AMT). The microelectrode platforms were characterized by FTIR, Raman, and microscopic techniques. The nitrate- and phosphate-based microneedle electrochemical sensors had excellent selectivity and sensitivity, with a determined limit of detection (LOD) of 0.008 mM and 0.007 mM, respectively. The pH microneedle sensor was responsive to pH in the linear range of 3-10. The three microneedle sensors yielded repeatable results, with a precision ranging from 4.0 to 7.5% RSD over the concentration ranges tested. The inexpensive (~ 1 $ CAD) microneedle sensors were successfully verified for use in quantification of nitrate, pH, and phosphate in brewed black coffee as a real sample. As such, the microneedle sensors are economical devices and show great promise as robust platforms for PON precision chemical analytics.
人们对农业食品安全和环境管理深感担忧，这就需要面向公众终端用户，开发出简单易用、成本低、耗时少的即时（PON）化学分析多路复用传感器。硝酸盐、磷酸盐和 pH 值的同步检测在土壤和水质分析、农业和食品质量评估中具有重要意义。本文展示了一系列不锈钢微针电化学传感器，用于通过循环伏安法衍生的法拉第电容作为检测模式，对 pH 值、硝酸盐和磷酸盐进行多路复用测量。多目标微针传感器通过层层（LbL）组装在不锈钢皮下微针基底上制造而成。对于硝酸盐传感，不锈钢涂有碳纳米管/纤维素纳米晶体（CNT）/CNC 修饰的银纳米颗粒（Ag）。对于 pH 值测量，将聚苯胺（pANI）涂覆到 CNT/CNC@Ag 薄膜上，而对于磷酸盐检测，将 CNT/CNC/Ag@pANI 微针进一步用四水合钼酸铵（AMT）修饰。通过傅里叶变换红外光谱（FTIR）、拉曼和显微镜技术对微电极平台进行了表征。基于硝酸盐和磷酸盐的微针电化学传感器具有出色的选择性和灵敏度，硝酸盐和磷酸盐的检测限（LOD）分别为 0.008 mM 和 0.007 mM。pH 微针传感器对 3-10 线性范围内的 pH 值有响应。三个微针传感器产生了可重复的结果，在测试浓度范围内的精度范围为 4.0-7.5%RSD。这些廉价（约 1 加元 CAD）的微针传感器已成功用于冲泡黑咖啡中硝酸盐、pH 值和磷酸盐的定量检测，可作为真实样本。因此，这些微针传感器是经济实惠的设备，作为 PON 精密化学分析的强大平台具有很大的应用潜力。
