Assessment of the effect of mineral acids and aluminum on the intensity of spectral lines of rare earth elements in atomic emission spectroscopy of microwave-induced plasma

E.O. Chibirev*, E.K. Konkova**, A.R. Garifzyanov***

Kazan Federal University, Kazan, 420008 Russia

E-mail: *chibirevegor@mail.ru, **redatushared@gmail.com, ***agar@live.ru

Received January 11, 2023; Accepted February 15, 2023

 

ORIGINAL ARTICLE

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DOI: 10.26907/2542-064X.2023.1.68-82

For citation: Chibirev E.O., Konkova E.K., Garifzyanov A.R. Assessment of the effect of mineral acids and aluminum on the intensity of spectral lines of rare earth elements in atomic emission spectroscopy of microwave-induced plasma. Uchenye Zapiski Kazanskogo Universiteta. Seriya Estestvennye Nauki, 2023, vol. 165, no. 1, pp. 68–82. doi: 10.26907/2542-064X.2023.1.68-82. (In Russian)

Abstract

To obtain reliable results in the quantitative determination of rare earth elements (REE) by atomic emission spectroscopy, it is particularly important to take into account the matrix effects of the macrocomponents contained in the analyzed solutions. Analytes obtained by liquid-phase and autoclave opening of geological samples of REE ores and minerals contain significant amounts of strong mineral acids used as reagents and such macrocomponents of the samples as aluminum (aluminosilicates) and phosphorus (phosphates in apatites). Here, we studied the effects of hydrochloric, nitric, sulfuric, and orthophosphoric acids and aluminum on the relative intensity of the ion analytical lines of La, Ce, Nd, Sm, Gd, Tb, Er, and Yb in atomic emission spectroscopy of the microwave-induced plasma (AES MIP). With an increase in the acid concentration from 0 to 1 mol/L, the relative intensity of the spectral lines of all investigated REE decreased monotonically by 10–20%. The depressing effect of aluminum, which is due to a decrease in the degree of ionization of REE atoms, was much stronger and reached 70%. It was shown that the AES MIP method is not inferior to atomic emission spectroscopy of inductively coupled argon plasma in terms of the detection limits of lanthanum, cerium, gadolinium, and erbium.

Keywords: atomic emission spectroscopy, microwave-induced plasma, rare earth elements, matrix interference, mineral acids, aluminum

Acknowledgements. This study was supported by the Kazan Federal University Strategic Academic Leadership Program (PRIORITY-2030).

Figure Captions

Fig. 1. Effect of the aluminum concentration on the relative intensity of spectral lines of rare earth elements E(II).

Fig. 2. Effect of the phosphoric acid concentration on the relative intensity of spectral lines of rare earth elements E(II).

Fig. 3. Effect of the HNO3, HCl, and H2SO4 concentrations on the relative intensity of La(II) – 394.9 nm.

Fig. 4. Effect of the HNO3, HCl, and H2SO4 concentrations on the relative intensity of Ce(II) – 446.0 nm.

Fig. 5. Effect of the HNO3, HCl, and H2SO4 concentrations on the relative intensity of Nd(II) – 430.4 nm.

Fig. 6. Influence of aluminum on the intensity of atomic and ion lines of rare earth elements with c(Al3+) = 0.28 M. The concentration of the measured metal ions is 2.8·10-4 mol/L.

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