A Convenient Strategy for the Voltammetric Direct Determination of Ce(III) in Environmental Waters Using a Multi-Walled Carbon Nanotubes Modified Screen-Printed Carbon Electrode

Abstract

A simple and fast stripping voltammetric procedure for trace determination of Ce(III) in environmental water samples has been developed. The procedure of cerium determination in the presence of Alizarin S and acetate buffer was employed as the initial method. The adsorption material, multi-walled carbon nanotubes, was used as a screen-printed electrode modifier ensuring efficient accumulation of the Ce(III)-Alizarin S complex. The calibration graph for Ce(III) for an accumulation time of 60 s was linear in the range from 1 × 10^-8 to 7 × 10^-7 mol L^-1 with the linear correlation coefficient r = 0.997. The detection limit was estimated from three times the standard deviation of low Ce(III) concentration and an accumulation time of 60 s was about 3.5 × 10^-9 mol L^-1. The proposed method was successfully applied to Ce(III) determination at trace levels in environmental water samples, such as river, lake and rain water with recoveries ranged from 93% to 98%.

Keywords: application; cerium; multiwalled carbon nanotubes; screen-printed electrode; stripping voltammetry method.

Figure 1

The effect of Alizarin S concentration on the cerium peak current. The pH of the acetate buffer was adjusted to 5.25 ± 0.05, Ce(III) concentration equal to 2 × 10⁻⁷ mol L⁻¹ in all examinations. Accumulation potential −0.3 V and accumulation time 60 s.

Figure 2

The effect of accumulation potential on the cerium peak current. The pH of the acetate buffer was adjusted to 5.25 ± 0.05, Ce(III) concentration equal to 2 × 10⁻⁷ mol L⁻¹, Alizarin S concentration equal to 5 × 10⁻⁵ mol L⁻¹ in all examinations. Accumulation time 60 s.

Figure 3

Cerium calibration curve and corresponding voltammograms. The Ce(III) concentrations: 1 × 10⁻⁸ (a), 3 × 10⁻⁸ (b), 5 × 10⁻⁸ (c), 1 × 10⁻⁷ (d), 3 × 10⁻⁷ (e), 4 × 10⁻⁷ (f), 5 × 10⁻⁷ (g) and 7 × 10⁻⁷ mol L⁻¹ (h).

Figure 4

The selectivity coefficients towards other metal ions. The metal ions were taken in a 100:1 ratio with respect to Ce(III).

Figure 5

The voltammograms obtained during cerium quantification in Czerniejówka river water diluted (1:10) containing 0.2 µmol L⁻¹ Ce(III) (a); as (a) + 2 × 10⁻⁷ mol L⁻¹ Ce(III) (b); as (a) + 4 × 10⁻⁷ mol L⁻¹ Ce(III) (c).

Figure 6

Schematic diagram showing the voltammetric measurement.