A possible steady state kinetic model for the atomization and excitation processes during inductively coupled plasma atomic emission spectrometry: Application to interference effects of lithium on calcium

Abstract

A possible steady state kinetic model is presented for the atomization and excitation processes during inductively coupled plasma atomic emission spectrometry. The model takes into account the relative rates of (a) thermal dissociation of analyte salt, (b) recombination of counter atom and analyte atoms, (c) charge transfer between analyte and interferent species, (d) charge transfer between analyte and argon species, and (e) ion/electron collisional de-ionization. Number density ratio data, n(u)'/n(u), where n(u) denotes the excited state and the prime denotes the presence of an interferent element, are presented showing that the predictions of the model are consistent with the signal enhancement observed at low analyte concentrations when Ca is determined by ICP in the presence of excess Li.

Toward a Fuller Understanding of Analytical Atomic Spectrometry

“…Each such mechanism is assumed to be kinetically controlled but to be in steady state at any given location in the plasma. 21,[40][41][42] The former assumption is widely held as being valid and the second is apparent from the fact the emission from any given volume element of the plasma is stable. For each hypothesized mechanism, a steady-state equation is formulated.…”

“…[17][18][19] This difference is critical, because Te is probably involved in atomic excitation and ionization, whereas Tg is important in dictating the kinetics of sample atomization. [21][22][23] In this brief paper, methods for measuring these important plasma features will be described and recent results obtained with them offered. The methods will be shown to offer insights into the mechanisms of matrix interference, of analyte atom and ion excitation, and the effect of an ICP-MS sampling cone on the plasma upstream of the sampling process.…”

Plasma Diagnostics through Kinetic Modelling: Characterization of Matrix Effects during ICP and Flame Atomic Spectrometry in terms of Collisional Radiative Recombination Activation Energy?A Review

“…Zaranyika et al [54,56] proposed a simplified reaction rate model that focuses on only one particular electronic level for the effect of EIEs in the air-acetylene flame and the ICP. Along with the simplified model, they proposed a novel method for probing changes in the number density of the analyte ground state and excited state, n o and n u respectively, based on determining the analyte absorbance (A) and emission (I) signal ratios A'/A and I'/I respectively, where the prime denotes presence of interferent, and comparing to theoretical values, n o '/n o and n u '/n u , derived assuming a simplified rate model based on steady state kinetics in the plasma.…”

“…The use of reaction rate models to probe excitation and deexcitation reactions occurring in the plasma has been attempted by several workers [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56], two approaches are employed: the Classical Collisional-radiative Rate Model approach and the Simplified Collisional-radiative Rate Model approach. Both models assume steady state kinetics within the plasma.…”

“…Two approaches have been proposed: (a) correlation of analyte emission with localized concentration maps of the analyte in the absence and presence of interferent species (Hieftje et al [19,52,53]), and (b) theoretical simulation of the signal enhancement ratio in the analytical zone of the plasma in the presence of EIEs [56][57][58][59][60].…”