Lanthanum(III) PVC membrane electrodes based on 1,3,5-trithiacyclohexane

Novel plasticized polymeric membrane (PPME) and membrane-coated graphite (MCGE) electrodes based on 1,3,5-trithiacyclohexane for highly selective determination of La(3+) ion have been developed. The electrodes exhibit Nernstian responses over very wide concentration ranges (8.0x10(-6)-5.0x10(-2) M for PPME and 4.0x10(-8)-1.0x10(-2) M for MCGE). The limit of detections were 5.0x10(-6) and 2.0x10(-8) M for PPME and MCGE, respectively. The electrodes possess a fast response time of similar to10 s and can be used for at least 6 months without observing any deviation. The proposed electrodes revealed excellent selectivities for La(3+) 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 La(3+) ions with EDTA and in determination of F(-) in some mouthwash preparations.