A microwave-induced plasma based on microstrip technology and its use for the atomic emission spectrometric determination of mercury with the aid of the cold-vapor technique

A new low-power, small-scale 2.45 GHz microwave plasma source at atmospheri c pressure for atomic emission spectrometry based on microstrip technology is described. The MicroStrip Plasma (MSP) source was produced in microstrip technology on a fused-silica wafer and designed as an element-selective de tector for miniaturized analytical applications. The electrodeless microwav e-induced plasma (MIP) operates at microwave input power of 10-40 W and gas flows of 50-1000 mL.min(-1) of Ar. Rotational (OH) and excitation (Fe) tem peratures were found to be 650 and 8000 K, respectively. Spatially resolved measurements of the Hg I 253.7-nm atomic emission line with an electronic slitless spectrograph (ESS) showed that a cylindrically symmetric plasma wi th a diameter of about 1 mm is obtained. With the MSP, Hg could be determin ed by applying the now injection cold vapor (FI-CV) technique with a detect ion limit of 50 pg.ml(-1). In terms of the relative standard deviation, a t ime stability of <1.4% for 45 replicates within 80 min can be realized at a concentration level of 10 ng.ml(-1) of Hg. Hg could be determined in the l eachate of a certified standard reference soil (STSD-4) obtained by treatme nt with aqua regia at the 930 +/- 76 ng.g(-1) level. Results obtained by ca libration with aqueous solutions of Hg and with standard addition were foun d to be in good agreement with those of cold-vapor atomic absorption spectr ometry.