Sensitive paper-based analytical device for fast colorimetric detection of nitrite with smartphone
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.
KeywordsPaper-based analytical device Nitrite Colorimetry Electrokinetic stacking Smartphone
Financial supports from the National Natural Science Foundation of China (21575019) and Educational Department of Liaoning Province (LZ2015036) are acknowledged.
Compliance with ethical standards
The saliva samples involved in this work were obtained from voluntary participants with informed consent. This study was carried out in accordance with the ethical principles for medical research involving human subjects as described by the World Medical Association.
Conflict of interest
The authors declare that they have no conflict of interest.
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