DETERMINATION OF TRACE-METALS USING AN ELECTROTHERMAL ATOMIZER BY LASER-INDUCED PLASMA ATOMIC EMISSION-SPECTROMETRY

A new technique for ultratrace elemental analysis at micrograms/liter and/or milligrams/liter concentration levels is examined. With this method, liquid samples are deposited inside a graphite furnace, then dried, ashed, and atomized from the walls of the graphite furnace. At the onset of the atomization cycle of the graphite tube, a pulsed Nd:YAG laser is triggered at 10 Hz and the output of the laser is focused inside the graphite furnace. The laser-induced plasma is then formed in the gas phase above the dried sample. As the temperature of the furnace is increased (by resistive heating), the analytes are volatilized and introduced into the laser plasma. The emission from this plasma is collected orthogonal to the direction of the original laser beam through the furnace dosing hole. The preliminary results presented here indicated that electrothermal atomization with laser plasma excitation is a promising technique for simultaneous multielemental analysis at trace and ultratrace levels. The lowest analyte masses determined were 5 and 50 pg with a RSD of 5% for cobalt and cadmium, respectively. Laser plasmas provide one of the highest temperatures reported for laboratory plasmas, therefore, minimizing or eliminating matrix interferences. Another advantage in using this technique is that analyses can be performed under atmospheric pressure.