GAS-PHASE RE-DISTRIBUTION OF ANALYTE SPECIES IN THE INTEGRATED CONTACT CUVETTE FURNACE ATOMIZATION PLASMA EMISSION-SPECTROMETRY SOURCE

Interactions of molecular and atomic analyte species released from the primary site of deposition of the sample into a heated integrated contact furnace have been studied with furnace atomization plasma emission spectrometry. With a 30 W forward power plasma, double peaks are observed in atomic emission during atomization of Cd, Pb, Ag, Mn, Cu, Fe and Co, reflecting early release of analyte from both the wall (primary site of deposition) and, subsequently, the radiationally-heated centre electrode (secondary release). With increased r.f. power, there is a corresponding early shift in all emission transients, reflecting plasma induced heating of both the tube wall and the centre electrode. At higher r.f. power, the centre electrode temperature is sufficient to prevent condensation of molecular species of Cd and Pb with the result that the second (late) peak for these elements is eliminated. Similarly, when the primary site for analyte deposition is the centre electrode, and the r.f. power is 50 W or more, transfer of analyte occurs and secondary release from the tube wall is observed. A directed internal convective flow of plasma gas in the char stage has a significant effect on this process.