An optical chemical sensor for thorium (IV) determination based on thorin

A selective method for the determination of thorium (IV) using an optical sensor is described. The sensing membrane is prepared by immobilization of thorin-methyltrioctylammonium ion pair on triacetylcellulose polymer. The sensor produced a linear response for thorium (IV) concentration in the range of 6.46 × 10−6 to 9.91 × 10−5 mol L−1 with detection limit of 1.85 × 10−6 mol L−1. The regeneration of optode was accomplished completely at a short time (less than 20 s) with 0.1 mol L−1 of oxalate ion solution. The relative standard deviation for ten replicate measurements of 2.15 × 10−5 and 8.62 × 10−5 mol L−1 of thorium was 2.71 and 1.65%, respectively. The optode membrane exhibits good selectivity for thorium (IV) over several other ionic species and are comparable to those obtained in case of spectrophotometric determination of thorium using thorin in solution. A good agreement with the ICP-MS and spiked method was achieved when the proposed optode was applied to the determination of thorium (IV) in dust and water samples.