Double resonance laser-induced fluorescence of Cadmium and Zinc in the inductively coupled plasma and electrothermal atomizer

Double resonance laser-induced fluorescence (LIF) spectrometry studies of Z n and Cd have been performed in the inductively coupled plasma (ICP) and el ectrothermal atomizer (ETA). Stepwise excitation of Zn is accomplished at 2 13.856 nm and 636.235 nm with fluorescence emissions observed near 334.5 nm . Excitation of Cd is accomplished at 228.802 nm and 643.847 nm with fluore scence emissions observed near 361.1 nm and 347.6 nm. Calibration studies d emonstrate that the double resonance LIF approaches provide high sensitivit y and linearity over several orders of magnitude in both atomizers. Limits of detection for Zn and Cd in the ICP are 1.7 ng/ml and 5 ng/ml, respective ly. Excellent sensitivity is observed in the ETA resulting in limits of det ection of 70 pg/ml (700 fg absolute mass) and 4 pg/ml (40 fg absolute mass) for Zn and Cd, respectively. The Zn content of a bovine serum standard ref erence material (NIST SRM 1598) has been determined by ETA-LIF and found to be 940 +/- 60 ng/g, which is in very good agreement with the certified val ue of 890 +/- 60 ng/g. Low-level ETA-LIF measurements of Zn in these studie s are strongly limited by the high background level observed for this eleme nt. (C) 1999 Elsevier Science B.V. All rights reserved.