A cobalt(II) ion-selective membrane sensor has been fabricated from a poly vinyl chloride (PVC) matrix membrane containing a new oxime compound (oxime of 1-(2-oxocyclohexyl)-1,2-cyclohexanediol, OXCCD) as a neutral carrier, sodium tetraphenyl borate (NaTPB) as an anionic excluder and o-nitrophenyloctylether (o-NPOE) as a plasticizing solvent mediator. The membrane sensor exhibits a linear potential response in the concentration range of 1.0 x 10(-1) - 1.0 x 10(-6) M of Co2+. The electrode displays a Nernstian slope of 29.8 mV decade(-1) in the pH range of 3.5 - 8.0. The sensor also exhibits a fast response time of < 25 s. The detection limit of the proposed sensor is 9.0 x 10(-7) M (approximately 40 ng/ml), and it can be used over a period of two months. The selectivity of the sensor with respect to other cations (alkali, alkaline earth, transition and heavy metal ions) is excellent. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of Co2+ with EDTA and for the direct determination of Co(II) in wastewater of the electroplating industry.
A highly selective and sensitive membrane electrode based on vanadyl salen complex (VS), which responds to monohydrogenphosphate (MHP) ions is described. The response of the sensor is Nernstian over the wide concentration range (1.0 Â 10 À1 À 5.0 Â 10 À6 M) of MHP. The sensitivity of the electrode is high enough to permit the detection of as little as 0.6 mg/mL of MHP without any significant interference from high levels of other anions. The potentiometric selectivity coefficient data revealed negligible interference from 11 common anions. The electrode has a fast response time (< 25 s), good slope stability at pH 8.2 for a period of at least eight weeks. It was successfully applied for the direct determination of monohydrogenphosphate in fertilizer and, as indicator electrode, in potentiometric titration of HPO 4 2À ion with barium chloride.
A PVC-based membrane sensor was prepared for Cs + ions, which was based on 7,11,15,28-tetraiodo-1,21,23,25-tetramethyl-2,20:3,19-dimethano-1H,21H,23H,25H-bis[1,3]dioxocino [5,4-i:5¢,4¢i¢] benzo [1,2-d:5,4-d¢]-bis[1,3]benzodioxocin stereoisomer (cavitand). The proposed membrane electrode exhibits a linear dynamic range of 1.0´10 -1 -1.0 × 10 -5 M, with a Nernstian slope of 59.1 ± 0.3 mV per decade, and a detection limit of 5.0´10 -6 M. It has a very fast response time of <10 s and can be used for at least eight weeks without any considerable divergence in its potentials. The best sensor performance was obtained with a membrane containing 30% PVC, 62% dibutylphthalate (DBP), 6% cavitand, and 2% potassium tetrakis(p-chlorophenyl) borate (KTpClPB). The sensor could be used in a pH range of 4.3-9.5.
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