A novel optical sensor is investigated for sensitive and selective colorimetric determination of chromium(III) depended on the immobilisation of 2-(2`-hydroxynaph-thylazo)benzothiazole (HNABT) on a triacetylcellulose (TAC) membrane. Cr(III) ions react with the immobilised reagent to cause an increase in the absorption of the optode at 578 nm in thiel buffer solution of pH 6.5. Total chromium was detected by reduction of Cr(VI) to Cr(III) with concentrated sulphuric acid and ethanol. The amount of Cr(VI) was evaluated by the concentration difference between the total Cr and Cr(III). The influences of reagent concentration, pH and response time on the immobilisation of HNABT were investigated. The optode exhibits a linear range of 3.0 × 10−9 to 5.0 × 10−5 mol L−1 of Cr(III) ion with detection and quantification limits of 8.5 × 10−10 and 2.9 × 10−9 mol L−1, respectively. The newly designed optode has a response time of about 3.0 min. The influence of various possible interfering species was established and it was represented that the optode has very excellent selectivity. From the obtained results, the proposed optode benefits from advantages such as high stability, low cost, relatively long lifetime, fast response time, reproducibility, low detection and quantification limits. An excellent selectivity for Cr(III) ion detection among a large number of cations and anions was emphasised. The performance properties of the proposed procedure are compared with those of some techniques previously reported. The optode can be regenerated readily with 0.025 mol L−1 HNO3 and its response is reproducible and reversible [RSD < 1.7]. The proposed optode was successfully used for the detection of Cr(III) in various biological and environmental samples |
