Use of a power divider for thermostated electrodeless discharge lamps in atomic fluorescence spectrometry

Abstract

In recent years, electrodeless discharge lamps (EDLs) have been put forth as intense sources for atomic spectrometry. However, it has not been until recently that work involving temperature-controlled (thermostated) EDLs has resulted in stable, intense, reliable EDL sources for atomic spectrometry. It has previously been demonstrated that single-and multielement EDLs are very sensitive t o temperature changes when operated with a thermostated antenna ( I , 2). The insensitivity of spectral output of EDLs operated with the thermostated "A"-antenna to changes in microwave power has been discussed previously (1-3). Some of the reasons given for using thermostated EDLs have been: microwave generators are difficult t o stabilize adequately, whereas air temperatures can be regulated with good precision; and changes in the coupling efficiency between the microwave field and the EDL discharge can, in the absence of temperature control, lead to drastic changes in lamp spectral output. Until recently ( 4 ) , one microwave generator per antenna had been used when operating EDLs. This is readily understood when one considers the myriad of papers on EDLs and the art and skill needed to utilize EDLs for analytical studies. However. with the insensitivity of thermostated EDLs to changes in microwave power, it is readily conceivable that more than one thermostated EDL could be operated simultaneously from one microwave generator utilizing a microwave power divider and that such a system would be very advantageous for multielement analysis. Norris and West ( 4 ) have reported the use of a two-port power divider for two dual-element EDLs and mentioned that it was a n economical means of illuminating a flame cell with radiation from more than one EDL simultaneously.In this study. thermostated EDLs operated a t their optimal temperatures and powered by one microwave generator using a power divider are evaluated. Detection limits for atomic fluorescence spectrometric measurement of several elements with these EDLs were obtained and compared with other published results.

Inductively coupled plasmas as atomization cells for atomic fluorescence spectrometry

“…The effect of lamp dimension and the amount of an element (or compound) charged into the lamp has not been investigated for the thermostated EDL's thus far, but comparison of EDL length and width (see Table III) with optimum temperatures indicate that EDL dimensions should not cause the temperature variation for these particular lamps. Because the procedure for the addition of element (or compound) to the quartz tube is not quantitative (19,20), different EDL's of the same element may contain different amounts of a particular element.…”