ULTRA-TRACE DETERMINATION OF CADMIUM BY VAPOR GENERATION ATOMIC FLUORESCENCE SPECTROMETRY

The vapour generation of cadmium by reaction in aqueous solution with sodium tetraethylborate was performed using a conventional continuous flow reactor. This vapour generation system was successfully interfaced with atomic absorption and fluorescence instrumentation. A detection limit, with fluorescence detection, of 20 ng dm-3 (3sigma(n-1)) was obtained after optimization of the chemistry using simplex routines. Interferences from transition metal ions (e.g., Ni(II), Cu(II)) were observed but were attenuated by the use of citrate as a masking agent. Vapour generation atomic fluorescence spectrometry was successfully applied to the determination of cadmium in potable waters, a National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1643c Trace Elements in H2O, and Community Bureau of Reference (BCR) Certified Reference Materials (CRMs) 144 Sewage Sludge-domestic and 145 Sewage Sludge-industrial. Full recovery of cadmium spikes was obtained from UK drinking waters. A value of 12.6 +/- 0.5 ng cm-3 of cadmium was obtained for NIST SRM 1643c (certificate value = 12.2 +/- 0.1 ng cm-3 of cadmium) whilst the cadmium content of BCR 144 and 145 (certificate value 3.41 +/- 0.25 and 18.0 +/- 1.2 mug g-1, respectively) was estimated at 3.34 +/- 0.15 mug g-1 (BCR 144) and 18.24 +/- 0.7 mug g-1 (BCR 145).