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

The graphite furnace atomic absorption spectrometry (GFAAS) method were dev eloped for the determination of chromium, molybdenum and vanadium dopants i n a bismuth tellurite (Bi2TeO5) matrix, using a transversely heated graphit e atomizer with longitudinal Zeeman background correction system. The bismu th tellurite matrix dissolved in HCl and modified by the addition of triamm onium citrate (TAC) was found to be significantly more volatile than the an alytes considered in the present analysis. Therefore, the matrix constituen ts could be removed by a selective vaporization during the pyrolysis step. By applying multiple sample dispension (5 x 20 mu l) and pre-vaporization o f the matrix, the calibration could be performed using simple, matrix-free standard solutions. Under mini-flow conditions (50 cm(3) min(-1)), the simu ltaneous GFAAS determinations of Cr, Mo and V in Bi2TeO5 crystals (single i njection) are characterized by the limit of detection (LOD) values of 0.83, 3.9 and 4.7 mu g l(-1), respectively, whereas in the presence of the matri x, 1.14, 4.9 and 6.7 mu g l(-1) are found, respectively. The latter LOD dat a correspond to 0.18, 0.78 and 1.1 mu g g(-1) Cr, Mo and V, respectively, i n the solid samples. The calibration curves of Cr, Mo and V are linear up t o 40, 100 and 400 mu g 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-vapo rization method, the LOD data of Cr, Mo and V an 0.16, 0.74 and 0.9 mu g l( -1) respectively, which correspond to 0.026, 0.12 and 0.14 mu g g(-1) Cr, M o and V, respectively, in the solid samples. (C) 2000 Elsevier Science B.V. All rights reserved.