Analytical Sciences

Hydroxy-Thioxanthones as Suitable Neutral Ionophores for the Preparation of PVC-Membrane Potentiometric Sensors for Al(III) Ion

Mojtaba SHAMSIPUR,*  Sohrab ERSHAD,* Absollah YARI,* Hashem SHARGHI,** and Ali Reza SALIMI**

*Department of Chemistry, Razi University, Kermanshah, Iran
**Department of Chemistry, Shiraz University, Shiraz, Iran

The complexation of five recently synthesized hydroxy-thioxanthone derivatives with Al³⁺ ion was studied in a methanol solution spectrophotometrically, and the stepwise formation constants of the resulting 1:1 and 2:1 (ligand-to-metal) complexes were evaluated. The suitability of the thioxanthone derivatives as neutral ionophores for the preparation of a new Al³⁺ ion-selective PVC-membrane electrode was investigated, and 1-hydroxy-3-methyl-thiocanthone was selected as the best compound for this purpose. The prepared electrode exhibits a Nernstian response for Al³⁺ ions over a wide concentration range (2.0 × 10^-2 to 2.0 × 10^-6 M), with a limit of detection of 1.0 × 10^-6 M. It has a very fast response time of about 5 s and can be used for at least 3 months without any considerable divergence in the potentials. The proposed membrane sensor revealed very good selectivities for Al³⁺ over a wide variety of other metal ions, and could be used at a working pH range of 3.4 - 5.0. It was used as an indicator electrode in potentiometric titration of aluminum ions with EDTA, and in the determination of Al³⁺ in different real samples.

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