Novel Hg2+-Selective Signaling Probe Based on Resorufin Thionocarbonate and its μPAD Application

Abstract

In this study, a novel resorufin thionocarbonate-based Hg 2+ -selective signaling probe ( RT ) for microfluidic paper-based analytical device ( μ PAD) applications is reported. The designed probe, RT , was readily synthesized by the one-step reaction of resorufin with phenyl thionochloroformate. The RT probe displayed a prominent color change from yellow to pink and a marked turn-on fluorescence signaling behavior exclusively toward the Hg 2+ ion. The signaling of RT was due to Hg 2+ -induced hydrolysis of the phenyl thionocarbonate moiety to form the parent resorufin dye, which restored its spectroscopic properties. In addition, RT exhibited the Hg 2+ -selective signaling behavior without interference by coexisting environmentally relevant metal ions. The detection limit for Hg 2+ in simulated wastewater samples was estimated to be 5.8 × 10 −8 M. In particular, an RT -equipped μ PAD prepared using a wax printing technique enabled simple and convenient determination of Hg 2+ ions in simulated wastewater samples, with a detection limit of 5.9 × 10 −6 M.

Simple and Equipment-Free Paper-Based Device for Determination of Mercury in Contaminated Soil

“…3.1 to 3.3 in Table 4 show PADs/µPADs techniques that were developed without using nanoparticles. Instead, these techniques utilized a chemical reaction to form a colored compound for semi-quantitative [ 24 ] or quantitative analyses of mercury [ 25 , 31 ]. Although these techniques do not produce Hg 0 , the chemicals employed are not eco-friendly.…”

“…It is also observed from Table 4 that all PADs/µPADs techniques developed in the last decade [ 25 , 26 , 27 , 28 , 29 , 30 , 31 ] were tested only in water samples (all spiked with mercury), which are not as complicated as soil. There were no alternative methods to the cold vapor-AAS for assessing soil contamination particularly for use in countries with limited resources.…”

“…For producing µPADs, patterns are drawn on the paper substrate using various hydrophobic materials to act as barriers to control the fluid flow on the paper. For mercury, there are some interesting paper-based devices that have been presented for colorimetric detection of mercury (as Hg 2+ ) with photographic image analysis [ 24 , 25 , 26 , 27 , 28 ]. Patidar et al presented two synthesized rhodamine derivatives for colorimetric detection of Hg 2+ (and Cr 3+ ) on paper strips and cellulose acetate membrane [ 24 ].…”

“…Patidar et al presented two synthesized rhodamine derivatives for colorimetric detection of Hg 2+ (and Cr 3+ ) on paper strips and cellulose acetate membrane [ 24 ]. A resorufin thionocarbonate signaling probe for Hg 2+ was recently synthesized by the group of Chang [ 25 ]. Hg 2+ induces cleavage reaction of thionocarbonate moiety of the probe leading to a prominent color change from yellow to pink.…”

“…The length of the pink reaction band increases linearly with the concentration of Hg 2+ . Most of these PAD/µPAD methods were tested to analyze water samples spiked with mercury [ 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. To the best of our knowledge, there has been no PAD/µPAD previously presented for detection of mercury in soil.…”