Ultra-trace determination of cadmium by vapour generation atomic fluorescence spectrometry

Abstract

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(3σ_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 µg g^–1, respectively) was estimated at 3.34 ± 0.15 µg g^–1(BCR 144) and 18.24 ± 0.7 µg g^–1(BCR 145).