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

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, CO 3 2– and SO 4 2– , 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.

Cesium Lead Bromide Perovskite Nanocrystals as a Simple and Portable Spectrochemical Probe for Rapid Detection of Chlorides

“…Hence, there is a need to monitor the concentration levels of chloride salts in water. Several techniques like titration, [3] spectrophotometry, [4,5] ion chromatography, [6] electrochemistry, [7] etc has been reported till date. Despite the high accuracy and precision of these techniques, they involve expensive instrumentation and is out of reach from on-site detection.…”

Distance-based detection of paracetamol in microfluidic paper-based analytical devices for forensic application

“…29,32 This technique has been particularly reported for the analysis of some target compounds such as iron, 29 copper, 29 aluminum, 33 nickel, 29 potassium, 34 calcium, 35 chloride, 36,37 ascorbic acid 38 and mercury, 39 where complexation reactions occur with their specific chromogen. Examples of classical acid-base, 40 argentometric, 37,41 and redox 42 titrations have been also reported using distance-based measurements on paper microfluidic devices.…”

“…Examples of classical acid-base, 40 argentometric, 37,41 and redox 42 titrations have been also reported using distance-based measurements on paper microuidic devices.…”

A Simple Distance Paper-Based Analytical Device for the Screening of Lead in Food Matrices

“…The measurement is simple, requiring only a readout of the color distance from the nearby ruler. Distance-based detection is one of the promising semi-quantitative analysis methods with superiority to the colorimetric detection-based method [ 13 , 14 , 15 , 16 , 17 , 18 ]. Several approaches have been proposed for improving the performance of the dPADs, such as using organic solvent to enforce the opening of wax valves, which facilitates reagent mixing and incubation in distance paper-based analytical devices [ 19 ].…”