Use of a low power, high frequency stabilized capacitive plasma combined with graphite furnace vaporization for the atomic emission spectrometric analysis of serum samples

The analytical figures of merit of a stabilized capacitive plasma using Ar and He as plasma gases in combination with electrothermal evaporation in a modified Perkin-Elmer HGA 500 graphite furnace are given. The plasma is operated at 27.12 MHz, at a power of 150 W and with a gas flow between 301/h and 1001/h. With sample volumes of 10 μl and Ar as plasma gas, detection limits for Ca, Cd, Cu, Fe and Mg were in the μg/l range. The absolute detection limits are at the 10–100 pg level. When using He as plasma gas, the detection limits are higher by a factor of 10–50 than for Ar. Easily ionized elements (Li, Na, K, Rb and Cs) depending on the use of argon or helium for Cd and Cu can cause both depression or enhancement of the emission intensity. In human serum, Cu, Fe and Mg could be determined without sample digestion. For the determination of Mg, the serum was diluted 1:100 with water and for the determination of Cu and Fe no dilution was applied. The analysis results of a reference sample are in good agreement with certified values.