Microdetermination of sulphate and organic sulphur: potentiometric back-titration using simple coated-wire electrodes

A method is describe for the determination of sulphate, based on precipitation with barium(II) chloride followed by potentometric back-titration of the excess of barium(II) salt sodium tetraphenylborate in the presence of polyethylene glycol. To monitor the titrations, simple ion-selective electrode...

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Bibliographic Details
Published in:Analytica chimica acta 1993-11, Vol.283 (1), p.645-649
Main Authors: Kalous, J., Brádova, D., Vytřas, K.
Format: Article
Language:English
Subjects:
Coated wire electrodes
Microdetermination
Potentiometry
Sulphur
Titrimetry
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Summary:A method is describe for the determination of sulphate, based on precipitation with barium(II) chloride followed by potentometric back-titration of the excess of barium(II) salt sodium tetraphenylborate in the presence of polyethylene glycol. To monitor the titrations, simple ion-selective electrodes of the coated-wire type were prepared using an ordinary aluminium conductor, coating the central wire with the membrane formed by plasticized poly(vinylchloride). The determination of organic sulphur consists in burning the sample in a flask filled with oxygen. The combustion products are absorbed in alkaline hydrogen peroxide and, in an aliquot. the sulphate formed is determined. The procedure was tested on eleven organic substances and applied to the determination of sulphur in samples of asphalt. Compared with visual detection of the direct titration of sulphate with barium(II) salt, the results are of the same precision and accuracy. The use of simple potentiometric sensors of the coated-wire type allows objective end-point evaluations and makes the procedure inexpensive.
ISSN:0003-2670
1873-4324
DOI:10.1016/0003-2670(93)85277-Q