Visual quantification of Hg on a microfluidic paper-based analytical device using distance-based detection technique

Maoxian Wang,Zhen Zhang,Chunxiu Xu,Yanling Fang,Yongshi Huang,Yuanhui Mo,Longfei Cai

doi:10.1063/1.4999784

Abstract

We presented a distance-based detection method for visual quantification of mercury ions on a microfluidic paper-based analytical device (μPAD). Dithizone in NaOH solution was used as chromogenic reagent and deposited onto paper channel delimited by hydrophobic wax barrier. Reactions happened between mercury ions and dithizone to form an insoluble colored complex, producing colored precipitate on the paper channel. The length of colored precipitate could be readily measured using the printed ruler along each device. The length of precipitate increase linearly with the mercury concentrations, mercury in sample solution could be quantified by measuring the length of the colored precipitate. Being free of any electronic instruments, this method has the advantages of portability, ease of use, low cost and disposability. This presented method was used to detect mercury ions in a synthetic sample, demonstrating its potential in on-site and real time analysis.

Highlights

Mercury ion, one of the most toxic heavy metals, has severe adverse effects on the human health and ecosystem
The ruler can be printed along the channel on each device to facilitate the length measurement. This method is free of any electronic instrument and timer and is independent of the lightening conditions, which are very attractive for on-site and real time assay of mercury ions by the untrained professionals especially in those resource-limited regions
As the solution wicked along the channel owing to the capillary action, mercury ions reacted with the colorimetric reagent deposited along channel to form an insoluble colored complex, which would precipitate onto channel to form a colored band (Figure 2C)

Summary

INTRODUCTION

One of the most toxic heavy metals, has severe adverse effects on the human health and ecosystem. In the presence of mercury ions, the paper channel embedded with Tb3+/BSA (bovine serum albumin)-AuNC undergo a distinct fluorescence colour change from red to green when illuminated by a UV lamp These methods are featured with high sensitivity, accuracy and selectivity, a confocal laser scanning microscopy or a UV lamp was required to excite the fluorescence, posing challenges for real time or on-site Hg assays by the untrained professionals. The ruler can be printed along the channel on each device to facilitate the length measurement This method is free of any electronic instrument and timer and is independent of the lightening conditions, which are very attractive for on-site and real time assay of mercury ions by the untrained professionals especially in those resource-limited regions

Chemicals and apparatus

Procedure for detection of Hg

Design and principle

Interference of foreign species

Sample analysis

Stability test

CONCLUSIONS