Indicator-Free Argentometric Titration for Distance-Based Detection of Chloride Using Microfluidic Paper-Based Analytical Devices.

Longfei Cai,Jiahong Song,Liye Yang,Zhuang Ouyang

doi:10.1021/acsomega.0c02143

Longfei Cai, Jiahong Song + Show 2 more

Open Access

https://doi.org/10.1021/acsomega.0c02143

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Journal: ACS omega	Publication Date: Jul 22, 2020
Citations: 18	License type: cc-by

Affiliation: Hanshan Normal University, Chaozhou Central Hospital

Abstract

We described an indicator-free argentometric titration strategy using a microfluidic paper-based analytical device. This strategy was based on the formation of insoluble silver salts by reactions occurring between analytes and titrant (Ag+) on a paper channel. After the insoluble silver salts were formed and precipitated on the channel, the paper substrate modified with the surplus titrant on the channel turned reddish-brown by exposure of the devices to a simple and cheap UV light source for 5 min, generating a colored band on the channel. Distance-based detection of chloride was achieved by measuring the length of the colored band with a detection limit of 1.7 mg L–1 Cl–. This method was used to detect chlorides in tap water, with an analytical result (10.1 ± 1.2 mg L–1) agreeing well with that obtained by a classical conventional precipitation titration (9.8 mg L–1), which was based on the measurement of the consumed volume of titrant. This paper-based precipitation titration method is free of skilled personnel and has advantages of low reagent/sample consumption, disposability, portability, and simple operation over the conventional precipitation titration. More importantly, being free of any indicator, this method may be used to detect more species than the conventional precipitation titrations, which are limited by the indicator, for example, CO32– and SO42–, which could form insoluble silver salts in aqueous liquids. Additionally, comparing with most of those paper-based titrimetry reported previously, this presented precipitation titration is free of any indicator or ion selective electrode to detect the end point of titration.

Highlights

The past decade has witnessed the fast development of a microfluidic paper-based analytical device since this concept was introduced by the Whitesides group.[1]
Its advantages of simple fabrication, easy operation, low cost, and disposability are very promising and attractive for point-ofcare analytical applications in clinical diagnostics,[2,3] environmental testing[4,5] and food safety monitoring.[6−8] Various detection techniques have been coupled to paper-based devices to obtain instrumental signals for quantitative analysis, including fluorimetry,[3,9] electrochemistry[10,11] and chemiluminescence assay.[12]
These abovementioned issues may be addressed by titrimetry on paper-based devices because titrimetry is free of any instrumental signals

Summary

■ INTRODUCTION

The past decade has witnessed the fast development of a microfluidic paper-based analytical device (μPAD) since this concept was introduced by the Whitesides group.[1]. Rahbar et al developed argentometric back-titration of chlorides via distance-based μPADs.[22] The principle of this method is very similar to the argentometric titration with a thread-based device reported previously.[23] this method is free of any electronic instrument (digital camera or scanner) and image processing software, an indicator solution was required to be deposited onto the channel besides the titrant and sample solution to generate a colored band. The precipitation titration on μPADs was based on the formation of insoluble silver chlorides produced by the reaction occurring between silver ions and chlorides on the paper channel: Ag+ + Cl− = AgCl. the paper channel was first modified with the titrant (silver nitrate solution) by adding titrant solution onto the channel with a micropipette (Figure 1B).

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES