Effect of sample matrix on the fundamental properties of the inductively coupled plasma

摘要

In the indutively coupled plasma (ICP),the emission intensities of atomic and ionic spectral lines are controlled by fundamental parameters such as electron temperature,electron number density,gas-kinetic temperature,analyte atom and ion number densities,and others.Accordingly,the effect of a sample matrix on the analyte emission intensity in an ICP might be attributable to changes in these fundamental parameters caused by the matrix elements.In the present study,a plasma imaging instrument that combines Thomson scattering,Rayleigh scattering,laser -indcued fluorescence and computed tomography has been employed to measure the above-mentioned parameters in the presence and absence of matrix elements.The data thus obtained were all collected on a spatially resolved basis and without the need for Abel inversion.Calcium,strontium and barium served as analytes,while lithium,commper and zinc were introduced as matrix elements.Comparing the data with and without the matrix elements allows us to determine the extent to which each fundamental parameter cahnges in the presence of a matrix element,and to better understand the nature of the matrix effects that occur in the ICP.As has been seen in previous stdies with different matrix elements,ion emission and ion number densities follow opposite trends when matrix interferents are introduced into the plasma:ion emission is enhanced by te presence of matrix interferents while ion concentrations are lowered.These changes are consistent with a shift from collisional deactivation to radiative decay of excited-state analyte species.