On-site rapid monitoring of nitrite as an assessment indicator of the environment, food, and physiological systems has drawn extensive attention. Here, electrokinetic stacking (ES) was combined with colorimetric reaction on a paper-based device (PAD) to achieve colorless nitrite detection with smartphone. In this paper, nitrite was stacked on the paper fluidic channel as a narrow band by electrokinetic stacking. Then, Griess reagent was introduced to visualize the stacking band. Under optimal conditions, the sensitivity of nitrite was 160-fold increased within 5 min. A linear response in the range of 0.075 to 1.0 μg mL⁻¹ (R² = 0.99) and a limit of detection (LOD) of 73 ng mL⁻¹ (0.86 μM) were obtained. The LOD was 10 times lower than the reported PAD, and close to that achieved by a desktop spectrophotometer. The applicability was demonstrated by nitrite detection from saliva and water with good selectivity, adding 100 times more concentrated co-ions. High recovery (91.0~108.7%) and reasonable intra-day and inter-day reproducibility (RSD < 9%) were obtained. This work shows that the sensitivity of colorless analyte detection-based colorimetric reaction can be effectively enhanced by integration of ES on a PAD.

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现场快速监测亚硝酸盐作为环境，食物和生理系统的评估指标已引起广泛关注。在此，将电动堆叠（ES）与比色反应结合在基于纸张的设备（PAD）上，以使用智能手机实现无色亚硝酸盐检测。在本文中，通过电动堆叠将亚硝酸盐以窄带的形式堆叠在纸的流体通道上。然后，引入格里斯试剂以可视化堆叠带。在最佳条件下，亚硝酸盐的敏感性在5分钟内增加了160倍。线性响应范围为0.075至1.0μgmL ^-1（R ²  = 0.99），检测限（LOD）为73 ng mL ^-1获得（0.86μM）。LOD比报告的PAD低10倍，与台式分光光度计接近。通过从唾液和水中进行亚硝酸盐检测（具有良好的选择性）证明了其适用性，并添加了100倍以上的浓缩共离子。获得高回收率（91.0〜108.7％）以及合理的日内和日间重现性（RSD <9％）。这项工作表明，通过在PAD上集成ES可以有效提高基于无色分析物检测的比色反应的灵敏度。

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