Chloride (Cl^-) is an inorganic anion present in a broad range of samples (e.g. biological, environmental, food, water, etc.), the determination of which is of widespread significance. In this work, we translate the well-established traditional argentometric method (Mohr's precipitation titration) into a small, simple, portable, and low-cost paper-based microfluidic diagnostic device, which provides rapid and quantitative analysis. The developed device enables the determination of chloride sample volumes as small as 5 μL. A distance-based detection method is implemented providing fully instrument-free quantitation. The beneficial effects of channel geometry (variable widths with constant heights) on analytical parameters were investigated. Trapezoidal channels (channel width changes linearly with height) were used to create a gradient of paper surface (titrant) available for the reaction, compared to the typical uniform rectangular channels (constant channel width). The trapezoid with increasing width offered higher sensitivity and lower detection limits (i.e. 0.05 mM vs 0.1 mM from the rectangular channel) for chloride determination across the concentration range of 0.05-25 mM. In addition, the effect of concentration of the deposited reagent on the obtained distance signals was investigated using varying concentrations of titrant (AgNO₃), which allowed determination of chloride across a wider dynamic range (up to 200 mM). The utility of the paper devices was demonstrated by determination of chloride in a variety of matrices including body fluids (sweat, serum, and urine) and water samples (drinking, mineral, river water).

Item Type:	Refereed Article
Keywords:	microfluidic paper-based analytical device, argentometric determination, distance-based measurement, chloride determination, asymmetric trapezoidal microfluidic channels
Research Division:	Chemical Sciences
Research Group:	Analytical Chemistry
Research Field:	Sensor Technology (Chemical aspects)
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Chemical Sciences
UTAS Author:	Rahbar, M (Mr Mohammad Rahbar)
UTAS Author:	Paull, B (Professor Brett Paull)
UTAS Author:	Macka, M (Professor Mirek Macka)
ID Code:	134569
Year Published:	2019
Web of Science® Times Cited:	4
Deposited By:	Austn Centre for Research in Separation Science
Deposited On:	2019-08-20
Last Modified:	2019-12-05
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