Solid sampling determination of magnesium in lithium niobate crystals by graphite furnace atomic absorption spectrometry

The vaporization/atomization processes of Mg in high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS) were investigated by evaporating solid (powder) samples of lithium niobate (LiNbO₃) optical single crystals doped with various amounts of Mg in a transversally heated graphite atomizer (THGA). Optimal analytical conditions were attained by using the Mg I 215.4353 nm secondary spectral line. An optimal pyrolysis temperature of 1500 °C was found for Mg, while the compromise atomization temperature in THGAs (2400 °C) was applied for analyte vaporization. The calibration was performed against solid (powered) lithium niobate crystal standards. The standards were prepared with exactly known Mg content via solid state fusion of the oxide components of the matrix and analyte. The correlation coefficient (R value) of the linear calibration was not worse than 0.9992. The calibration curves were linear in the dopant concentration range of interest (0.74–7.25 mg/g Mg), when dosing 3–10 mg of the powder samples into the graphite sample insertion boats. The Mg content of the studied 19 samples was in the range of 1.69–4.13 mg/g. The precision of the method was better than 6.3%. The accuracy of the results was verified by means of flame atomic absorption spectrometry with solution sample introduction after digestion of several crystal samples. - Highlights: • SS-HR-CS-GFAAS methods were studied for determining Mg dopant in powered LiNbO_3. • Optimal conditions were attained using the Mg line at 215.4353 nm. • Optimal T_pyr of 1500 °C was found by recording the pyrolysis curve. • Compromise T_at of 2400 °C was found by recording the atomization curve. • Accuracy of the results was checked by FAAS using solutions of digested crystals.