Paper-based cation-selective optode sensor containing benzothiazole calix[4]arene for dual colorimetric Ag+ and Hg2+ detection.

A new paper-based analytical device based on bulk ion-selective optodes (ISOs) for dual Ag+ and Hg2+ detection has been developed. A plasticized PVC hydrophobic phase composed of 25,27-di(benzothiazolyl)-26,28-hydroxycalix[4]arene (CU1) as an ion-selective ionophore, potassium tetrakis(4-chlorophenyl)borate as an ion-exchanger and chromoionophore XIV as a lipophilic pH indicator was entrapped in the pores of cellulose paper. This paper strip showed higher selectivity for Ag+ and Hg2+ over common alkali, alkaline earth and some transition metal ions with a color change from blue to yellow. With the proposed sensor, Ag+ and Hg2+ can be measured with the range of 1.92 × 10-6 to 5.00 × 10-3 M for Ag+ and 5.74 × 10-7 to 5.00 × 10-5 M for Hg2+ with a limit of detection of 1.92 × 10-6 M for Ag+ and 5.74 × 10-7 M for Hg2+. The proposed sensor was successfully applied to determine the amount of mercury in various water sources and the amount of silver in cleaning product samples containing silver nanoparticles (AgNPs). The results were in good agreement with inductively couple plasma-optical emission spectrometric measurements (ICP-OES).