The use of different sample introduction techniques in combination with the low power stabilized capacitive plasma (SCP) as a radiation source for atomic emission spectrometry

Abstract

The analytical figures of merit of atomic emission spectrometry with the stabilized capacitive plasma (SCP), operated at 27.12 MHz with a power of 150 W and a gas flow between 60 l/h and 120 l/h Ar in combination with hydride generation for As, as well as with electrothermal evaporation and pneumatic nebulization with subsequent desolvation for sample introduction are described. Two methods for the generation of the volatile AsH 3 were applied. The possibilities of a micro method using sample dispensing on a NaBH 4 pellet is compared to continuous hydride generation using a NaBH 4-solution. The detection limits for As have been found to be 0.5 μg/ml or 5 ng absolute, respectively for the micro method and 40 ng/ml for the continuous hydride generation. Electrothermal evaporation from a tungsten filament was combined with the SCP. Using 10 μl of sample solution and Ar, He or Ar H 2 as plasma gas, detection limits in the ng/ml range were obtained for Cu, Cd, Ca and Mg. The absolute detection limits are at the 100 pg level. The detection limit for Fe is 1 μg/ml when using Ar as plasma gas because of spectral interferences with the tungsten evaporated from the filament, but could be improved by a factor 10 when adding 0.5% (v:v) H 2 to the Ar. Because of the robustness of the SCP it is possible to use pneumatic nebulization with subsequent desolvation as sample introduction technique. With Ar as plasma gas detection limits in the 10–100 ng/ml range were obtained for Cu, Cd, Fe, Mn, Ca, Mg and Sr. The calibration curves are linear over three to four orders of magnitude from the detection limit on.