SU1476370A1 - Inversion-voltamperic method of analysing hydrovanadate ions in aqueous solutions - Google Patents

Abstract

This invention relates to the field of analytical chemistry, in particular, to inversion voltamperometric methods for determining anions in aqueous media. The purpose of the invention is to increase sensitivity, selectivity, as well as improve the hygienic conditions of def. The goal is achieved by concentrating gidrovanadate ions on the surface of a silver disc electrode in the potential range from 0.34 to 0.38 V against the background of perchlorate alkali metal solutions or sodium tetraborate buffer solution at pH 9-11.2. Then, a cathode voltammogram is recorded from 0.34 to -0.30 V at a voltage sweep rate of 20-60 tV / s. The concentration of hydrovanadate ions is determined by the peak height in the potential range from 0.13 to 0.20 V. 1 sludge.

Description

one

The invention relates to analytical chemistry, in particular, to inversion voltamperometric methods for determining anions in aqueous media, and can be used in determining the microconcentration of vanadium (V) present in solution in the form of a hydrovanadate ion.

The purpose of the invention is to increase the sensitivity, selectivity of the determination of gidrovanadate ions, as well as to improve the hygienic working conditions.

The drawing shows a voltamogram of the dissolution of silver hydrovanadate.

As a background electrolyte, a 0.1 M perchlorate alkali metal solution with a pH of 9-11 or a buffer solution of 0.05 M sodium tetraborate with a pH of 9-11 can be used. The reproducibility of the results strongly depends on the pH of the solution, therefore it is preferable to use buffer solutions. In this region, the pH of the vanadate ion is in the form of hydrovanadate. The potential range of electrolysis for tetraborate buffers (0.34–0.36 V) and for perchlorate solutions of alkali metals, in particular for 0.1 M NaClO with pH 9-11 (0.36–0.38 V), is due to that the dependence of the peak of dissolution of the precipitate on the potential passes through a maximum, and this maximum is in the indicated potential intervals.

The cathode linear potential sweep rate varied within 20–60 mV / s, where the recording quality of polarization curves is the best (for the PU-1 device). The cathode peak potential of sediment dissolution is in the range of 0.130-1.190 V for tetraborate buffer solutions and 0.14-0.20 V for 0.1 M perchlorate solutions relative to the saturated calomel electrode.

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Example 1. To 15 ml of a 0.05 M sodium tetraborate buffer solution with a pH of 9.18, add a few drops of the vanadate-ion-containing solution for the purpose of quantitative. aptly defined. The resulting solution is placed in a polarographic cell. A silver electrode with a well polished surface (using a moistened chromium oxide powder) and a thoroughly washed surface is immersed in the solution cell. The solution is purged with an inert gas (high purity argon) for 15 minutes to remove oxygen, followed by electrolysis at a potential of 36 V relative to a saturated calomel electrode. Duration of electrolysis min. After the time of electrolysis, a cathode peak is recorded at a linear potential sweep to the cathode region at a speed of k) 20 mV / s until the precipitate dissolves. The cathodic peak of the dissolution of the hydrovanadate ion is fixed on the chart tape. Measuring the height of the peak, the concentration of the hydravanadate ion was determined according to a calibration curve constructed from standard solutions.

Example 2. To a decimolar solution of sodium perchlorate was added a solution of 0.5 M KOH to a pH of 10-11. 15 ml of the prepared background solution is taken into the polarographic cell and a few drops of the solution containing van adat ions are added to determine its content. The silver electrode is immersed into the solution cell with the surface polished to a mirror shine and thoroughly washed bidistille. A hermetic electrochemical cell with a solution is purged for 15 minutes with an inert gas (high purity argon) to remove dissolved oxygen, followed by electrolysis at a constant potential of 36 V relative to a saturated calomel electrode. Duration of electrolysis min. After 5 minutes, a cathode peak is recorded at a linear potential sweep.

in the cathode region with a speed of mV / s. The cathode peak is recorded on a chart tape. By measuring the height of the peak, the concentration of the hydrovanadate ions is determined using a calibration curve or an additive method.

Curve 1 represents the background line; on curve 2, the polarization curve for the dissolution of the precipitate; 2, on curve 3, the polarization curve for the dissolution of the Snuo precipitate.

The determination of gidrovanadate ions does not interfere with a tenfold excess of chloride, bromide, fluoride, and acetate ions, and approximately equal amounts of iodide ions interfere with the determination.

The minimum detectable concentration of the hydrovanadate ions in the solution is 1-10-7M.

The standard error in determining the minimum concentration does not exceed 11%.

Claims (1)

Invention Formula An inversion voltamperometric method for determining gidrovanadat-ions in aqueous solutions by concentrating the detected ions on the electrode surface in the form of a poorly soluble precipitate followed by recording the volt-ampere-dissolving curves, in order to increase the sensitivity, selectivity of determination, as well as improve hygienic working conditions , the hydrovanadate ions are concentrated on the surface of the silver electrode in the potential range of 0.34–0.38 V against the background of perchlorate alkali solutions. or in buffer solutions of sodium tetraborate at pH 9.0–11.2, followed by recording cathode polarization curves in the potential range of 0.34–0.30 V with a linear sweep rate of polarizing voltage of 20–60 mV / s, and the concentration of gidrovanadate ions is determined by the height of the peak in the range of potentials of 0.13-0.20 V. # J4 0.-GA-0.06 -0.26 Ev