RAPID SAMPLE PRECONCENTRATION BY SPRAY DEPOSITION FOR ELECTROTHERMAL VAPORIZATION INDUCTIVELY-COUPLED PLASMA SPECTROMETRY

The deposition of aqueous sample in an electrothermal vaporization unit (ETV) is implemented by spraying onto a graphite tube heated at 160 degrees C. The water is evaporated continuously and vented by a flow of argon, leaving the analytes on the inner walls of the graphite cuvet. The analytes are later atomized at high temperature and directly to an inductively coupled plasma for atomic emission spectrometry (ICP-AES). The effects of observation height, argon flow in the furnace unit at atomization, and plasma energy on the signal-to-noise ratio were studied. The combination of the advantages of ETV with a sample volume of 1 ml provides detection limits for Cd (0.06 ng/ml), Pb (0.3 ng/ml), Zn (0.02 ng/ml) and Cu (0.04 ng/ml) which are an improvement of two orders of magnitude when compared with conventional nebulization. Moreover, the ETV allows a more convenient interface to the plasma than similar direct sample insertion (DSI) experiments.