Determination of chromium, molybdenum and vanadium dopants in bismuth tellurite optical crystals by multi-element graphite furnace atomic absorption spectrometry

Abstract

The graphite furnace atomic absorption spectrometry (GFAAS) method were developed for the determination of chromium, molybdenum and vanadium dopants in a bismuth tellurite (Bi 2TeO 5) matrix, using a transversely heated graphite atomizer with longitudinal Zeeman background correction system. The bismuth tellurite matrix dissolved in HCl and modified by the addition of triammonium citrate (TAC) was found to be significantly more volatile than the analytes considered in the present analysis. Therefore, the matrix constituents could be removed by a selective vaporization during the pyrolysis step. By applying multiple sample dispension (5×20 μl) and pre-vaporization of the matrix, the calibration could be performed using simple, matrix-free standard solutions. Under mini-flow conditions (50 cm 3 min −1), the simultaneous GFAAS determinations of Cr, Mo and V in Bi 2TeO 5 crystals (single injection) are characterized by the limit of detection (LOD) values of 0.83, 3.9 and 4.7 μg l −1, respectively, whereas in the presence of the matrix, 1.14, 4.9 and 6.7 μg l −1 are found, respectively. The latter LOD data correspond to 0.18, 0.78 and 1.1 μg g −1 Cr, Mo and V, respectively, in the solid samples. The calibration curves of Cr, Mo and V are linear up to 40, 100 and 400 μg l −1, respectively. The characteristic masses are 7.5 pg Cr, 20 pg Mo and 58 pg V. For the multiple dosing and matrix pre-vaporization method, the LOD data of Cr, Mo and V are 0.16, 0.74 and 0.9 μg l −1, respectively, which correspond to 0.026, 0.12 and 0.14 μg g −1 Cr, Mo and V, respectively, in the solid samples.