Lanthanum(III) PVC Membrane Electrodes Based on 1,3,5-Trithiacyclohexane

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Abstract
Novel plasticized polymeric membrane (PPME) and membrane-coated graphite (MCGE) electrodes based on 1,3,5-trithiacyclohexane for highly selective determination of La3+ ion have been developed. The electrodes exhibit Nernstian responses over very wide concentration ranges (8.0 × 10-6−5.0 × 10-2 M for PPME and 4.0 × 10-8−1.0 × 10-2 M for MCGE). The limit of detections were 5.0 × 10-6 and 2.0 × 10-8 M for PPME and MCGE, respectively. The electrodes possess a fast response time of ∼10 s and can be used for at least 6 months without observing any deviation. The proposed electrodes revealed excellent selectivities for La3+ over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in a pH range of 5.0−8.0. The practical utility of the electrodes has been demonstrated by their use as indicator electrodes in the potentiometric titration of La3+ ions with EDTA and in determination of F- in some mouthwash preparations.