Sulfate-Selective Electrode of Poly(vinyl chloride) Membrane Impregnated with Barium Chloranilate

Abstract

A solid-state heterogeneous membrane electrode that is selective to sulfate ions was prepared from a poly(vinyl chloride) membrane impregnated with barium chloranilate. Although the electrode response was under Nernstian (16 mV/pSO42-) it was applicable to a sulfate concentration range of 10-1.5 to 10-4 mol dm-3. The preferable pH range was 6 -11 and the response time was about 30 s. Sulfate ions in organic compounds and polymers can be assayed with this electrode without serious errors at low concentrations of various interfering anions. The electrode remained active for at least 300 measurements, or 3 months. KeywordsIon-selective electrode, sulfate-sensitive membrane electrode , barium chloranilate, poly(vinyl chloride)Various organic sulfur compounds are widely used in such industries as agrochemicals and drugs. However, there are few satisfactory methods for the determination of sulfate ions in such compounds. One method is to decompose organic sulfur compounds in a combustion flask followed by sulfur determination by gravimetryl or ion chromatography.2,3 A photometric method for the determination of sulfate ions in natural water or rain was also proposed which uses barium chromate or barium chloranilate.4,5Recently, chloranilic acid has been used in precipitation titrations with biamperometric end-point detection for the indirect determination of sulfate and phosphate ions.6' Ion-selective electrodes are useful for ionactivity measurements in many fields; anion-selective membrane electrodes have been described by Pungor.8 Highly selective electrodes for iodide, chloride and bromide were developed using a precipitate-impregnated membrane electrode.9-11 Attempts have also been made to construct electrodes that are selective to sulfate or phosphate ions.12 The usefulness of the sulfate-and phosphate-sensitive membranes proposed by Pungor was examined by Rechnitz.13 Strivastava and Jamn have discussed a solid-state heterogeneous sulfate membrane of polystyrene in which hydrous thorium oxide powder was dispersed.14 The construction and application of a chloranilate liquid-membrane electrode were reported by Veltsistas and Karayannins.15 We have also studied the determination of sulfate ions in seawater or of sulfur as sulfate ions in organic compounds using a sulfateselective electrode. 16 In this paper we describe the electrochemical performance of a polyvinyl chloride) membrane electrode impregnated with barium chloranilate, which can be used for the determination of sulfate ions in organic compounds, polymers and seawater. This electrode exhibits high selectivity to sulfate ions and suffers only little due to interference from other ions at lower concentrations. ExperimentalReagents and apparatus All of the reagents were of analytical grade. Barium chloranilate (CLB, Dojindo Co.) and poly(vinyl chloride) (PVC, Wako Pure Chemical Co.) were used as received. A standard sulfate solution (1.0X10-1 M; M= mol dm 3) was prepared by dissolving 17.426 g of potassium sulfate (Nacalai Tesque Co.) in 1000 cm3 of deioniz...

Stacking of metal chelating rings with π-systems in mononuclear complexes of copper(ii) with 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone (chloranilic acid) and 2,2′-bipyridine ligands

“…[13][14][15][16][17][18][19][20][21] Substituents on the quinoid ring influence its electronic structure: electron-withdrawing ones, such as -CN, -NO 2 or halogens, raise the oxidation potential, while electron-donating ones, such as -OH, -OCH 3 , -CH 3 or -NH 2 lower it. Due to their oxido-reduction properties, quinones exist in biological systems, mainly in bioenergetical processes, such as respiration and photosynthesis, 22 but they also have a wide application in electrochemistry 23 and analytical chemistry. 24 The coordination compounds of 2,5-dihydroxybenzoquinone were examined thoroughly, including low-nuclear to polymeric species.…”