Determination of the Content of Sulfate Ions in Drinking and Mineral Waters and Oxalate Ions in Tea with Direct Potentiometry Method E.M. Rakhmanko†, Yu.V. Matveichuk*‡
	* Corresponding authors † Belarussian State University, Leningradskay, 14, 220030, Minsk, Belarus ‡ Mogilev State University of Food Technologies, Shmidta, 3, 2120127, Mogilev, Belarus E-mail: Yu_Matveychuk@mail.ru
	Methods Objects Chem. Anal., 2015, 10(2), p. 61-66 https://doi.org/10.17721/moca.2015.61-66
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Abstract

The analytical methods for determining oxalate and sulfate ions in tea, mineral and drinking waters, respectively, with direct potentiometry in a variant of the calibration curve using film oxalate and sulfateselective electrodes based on the higher of quaternary ammonium salts, which membrane plasticized with 1-bromonaphthalene, were developed. To increase the affinity of the hydrophilic SO₄^2- and C₂O₄^2- ions to the hydrophobic phase of the membrane and to increase of the electrode selectivity to basic ion (C₂O₄^2- and SO₄^2-) was injected into the neutral carrier membranes - heptyl ester n-trifluoroacetylbenzoic acid. The relative deviation Sr results of detection sulfate ions in drinking and mineral waters is 4-9%, the oxalate ions in tea is not more than 7% and is not more than 5% (as determined by the method of additives). Gravimetric determination of sulphate ions as the reference methods of analysis was used. Accuracy and reproducibility of results of С₂O₄^2- ions determination were tested with additive method with followed diluting.

Keywords: ion-selective electrode, direct potentiometry, oxalate ions, sulfate ions, quaternary ammonium
salts

Article language: Rus