Preliminary investigations of high-frequency atmospheric-pressure plasma jet for atomic emission spectrometry

The 27.12- and 13.56-MHz plasma-jet discharges are generated in argon at at mospheric pressure. The plasma originates inside the nozzle of the bored me tal power electrode and outflows against the counter-elect rode. The discha rge has a column shape with the diameter about 0.7-1.5 mill and the length 5-30 mm. The 27.12 MHz/100 W and 13.56 MHz/1 500 W generators are operated at a power of 100 and 200 W, respectively. Stable discharges are obtained w ithin the range from 0.3 to 0.9 dm(3) min(-1) Ar. The 27.12 MHz/100 W disch arge is capable of accepting dry aerosol while the wet aerosol extinguishes this plasma. Oil the contrary, wet aerosol can be introduced into the 13.5 6 MHz/200 W plasma. The vibrational temperature of 3 000 K has been determi ned based oil the intensity of the molecular band of the N-2 2nd positive s ystem (365-383 nm) in the 27.12 MHz discharge. Intensity vs concentration d ependences have been measured with Li 670.784, Na 588.995, Na 589.592, K 76 6.491 and Rb 780.023 nm lines. Limits of detection in the 27.12 MHz/100 W d ischarge coupled to an ultrasonic nebulizer with desolvation are 0.1 Li, 30 Na, 10 K and 3 ng cm(-3) Rb. Limits of detection in the 13.56 MHz/200 W di scharge connected to a pneumatic concentric Meinhard nebulizer is 8 ng cm(- 3) Li.