Development of a selective bulk optode membrane containing benzothiazole calix[4]arene for determination of silver ion

Abstract

The aim of this research was to fabricate the optode membranes for determination of silver ion in real sample. The optode membrane incorporating 10.94 mmol kg⁻¹ of 25,27 -di(benzothiazolyl)-26,28-dihydroxycalix[4]arene (CU1) as a silver-selective ionophore, 5.98 mmol kg⁻¹ of Chromoionophore l as a proton selective neutral chromoionophore and 7.47 mmol kg⁻¹ of potassium tetrakis (4-chlorophenyl borate) KTpCLPB) as an ion-exchanger plasticized in PVC membrane (29.5 mg) using 59.1 mg of bis(2-ethylhexyl) sebacate (DOS) as plasticizer were prepared. The fabricated optode membranes can be kept within 2 weeks before using with good reproducibility. It responded to silver ion by changing in the absorption of chromoionophore at pH 8.0-8.5 within the response time of 10 min. It also provided a calibration response over a wide concentration range of 10⁻⁵-10⁻² mol L⁻¹. The lower detection limit of 7.83x10⁻⁶ mol L⁻¹ and the upper detection limit of 1.58x10⁻² mol L⁻¹ were obtained. Moreover, the optode membrane could be reused immersing in 1 mol L⁻¹ HNO₃ solution for 5 min. The proposed optode membrane displayed a good selectivity toward silver ion over other cations in the order of silver ion > sodium ion > potassium ion > mercury ion > calcium ion. Finally, the fabricated optode membranes were successfully applied to determine silver ion in cleansing water with the percentage recovery of 92-93%. They also provided the percentage recovery in the range of 104-109% in the case of silver nanoparticles solution by spiked method.