Emission Line Enhancement in a dc Plasma

Abstract

Emission line enhancement in a dc plasma seeded with an easily ionizable matrix salt is discussed. Enhancement is shown to be inversely related to the ionization potential of the matrix element. The temperature of the plasma core is shown to decrease in the presence of an easily ionizable element, while the effective temperature experienced by the analyte is shown to increase under the same conditions. The emission of the plasma is spatially profiled with and without an easily ionizable matrix element at the 425.4 nm Cr line, the 340.5 nm Co line, and the 334.5 nm Zn line.

Spatially resolved laser-induced fluorescence studies on a three-electrode direct current plasma

“…The SpectraJet HI three electrode direct current plasma (DCP) has attracted more interest than previous DCP designs [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49]. This is mainly due to its success as an atomic emission source; detection limits have been reported [33,37] to be less than 1 ppm for many elements.…”

“…At higher positions in the plasma, the behaviour of the analyte becomes more complex as it approaches the steep thermal gradients at the centre of the plasma. These thermal gradients have been measured in spatially resolved experiments [33,46] and may be as high as several thousand K per millimeter. These gradients act as thermal barriers whose effects in the plasma can be seen This figure shows that the saddle shape, or twin peaks in the Y dimension, was probably caused by the creation of Ba + in the higher energy zones of the plasma.…”

Application of signal enhancement by easily ionized elements in hydride generation direct current plasma atomic emission spectrometric determination of arsenic, antimony, germanium, tin, and lead

“…Signal enhancement by easily ionized elements (EIE) in direct current plasma atomic emission spectroscopy (DCP-AES) has been encountered for over 2 decades (1)(2)(3)(4). In the presence of easily ionized elements, such as alkali elements and alkaline-earth elements, analytical signals of other elements are usually increased.…”

“…In the presence of easily ionized elements, such as alkali elements and alkaline-earth elements, analytical signals of other elements are usually increased. Although emission line to background ratios are often improved as well, this enhancement effect has been generally regarded as nuisance (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) due to its unpredictability. For DCP-AES determinations, variable EIE concentrations in different sample matrices make the accurate determination difficult.…”

“…Later research, however, showed that intensities of both atomic and ionic emission lines were enhanced and that the addition of EIE appeared to have little influence on electron densities measured in the analytical zone (16,20,21). With more detail study, a number of mechanistic models have suggested possible explanations of this complex phenomenon (3,8,22,23).…”