A new sensor membrane based on immobilization of 4-hydroxy salophen on triacetyl cellulose has been developed for the determination of Cd(II) ions that displays excellent performance. The sensing membrane is capable of spectrophotometric determining of Cd(II) with an outstanding high selectivity over a dynamic range between 1.0 times 10<sup>-6</sup> and 5.0 times 10<sup>-2</sup> mol L<sup>-1</sup> with a limit of detection of 5.3 times 10<sup>-7</sup> mol L<sup>-1</sup> (0.06 mug mL<sup>-1)</sup>. The sensor shows a fast response time (< 5 min) and the membrane can be used for more than two months without observing any major deviation. The optode revealed very good selectivity with respect to many cations including alkali, alkaline earth, transition and heavy metal ions. The proposed sensor could be used to determine cadmium ions in water and waste water samples. Different experimental parameters such as variable affecting on sensor preparation and pH of the sample solution plus response time were studied. The optodes developed in the present work were found to be stable, cost effective, easy to prepare, and efficient for direct determination of Cd(II) in a variety of aqueous samples using spectrophotometry, with satisfactory results.
8 Figures and Tables
Fig. 1. Schematic diagram of the homemade cell.
Fig. 2. Structure of 4-hydroxy salophen.
Fig. 3. Possible schemes of reaction between 4-hydroxy salophen with the activated membrane.
Fig. 5. Influence of pH on immobilization of the ligand on triacetylcellulose membrane. Conditions: time of hydrolysis, 24 h; time of immobilization, 5 h; 4-Hydroxy-salophen, 0.020% (w/v); pH of immobilization, 6.2.
Fig. 6. Influence of pH of the sample solution on the sensitivity of sensor. Conditions: time of hydrolysis, 24 h; time of immobilization, 5 h; pH of immobilization, 6.2; Cd(II), 1.0 ; 4-Hydroxy-salophen, 0.020% (w/v).
Fig. 7. The relative standard deviation for: (a) 1.0 ; (b) 5.0 ; and (c) 5.0 Cd(II) solutions at the optimum conditions.
Fig. 8. Calibration curve for determination of Cd(II) using the optode. (a) Absorbance versus wavelength for (1) 5.0 , (2) 5.0 , (3) 5.0 , (4) 1.0 , and (5) 1.0 Cd(II). (b) Absorbance versus under the optimized conditions.
TABLE I DETERMINATION OF CD(II) IN REAL SAMPLES
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