Comparison of matrix effects on atomic emission spectrometers with nitrogen microwave induced plasma

Abstract

The creation and implementation of new sources of sample excitation and spectrometers based on them into the practice of analytical laboratories raises many questions for researchers about the obtained analytical characteristics of new equipment and analysis methods. The most important characteristics of any method include detection limits, accuracy and reproducibility of the results obtained. Matrix elements can have a significant effect on these parameters. The paper shows a comparison of the change in the intensities of analytical lines of elements in the presence of matrix elements with ionization potentials of 5.13 - 10.48 eV (Na, Cu, Pb, Cd, Zn, In, Ga, Bi) in the concentration range of 0 - 1 wt %. on commercially available atomic emission spectrometers with microwave plasma Grand-MP ("VMK-Optoelektronika") and Agilent MP-AES 4100 (Agilent Technologies). It is shown that the magnitude of the matrix effect in these excitation sources depends on the ionization potential of the matrix element and the total energy of the analyte line. A significant effect of matrix elements with a concentration of up to 1% wt. on the intensity of spectral lines of atoms and ions of the sample. Elements with medium and high ionization energies practically do not affect the intensity of atomic spectral lines of impurity elements and lead to a decrease in the intensity of ionic lines. The influence of easily ionized elements is more pronounced - both depressing and amplifying effects are observed, probably caused by both a change in the concentration of electrons in the plasma, leading to a linear change in the equilibrium between atoms and ions, and a decrease in the plasma temperature. An increase in the power supplied to the plasma on the Grand-MP spectrometer leads to a decrease in the effect of easily ionized elements on the intensity of the spectral lines of the elements. It is shown that the plasma in the Grand-MP spectrometer has better resistance to matrix influences as compared to the Agilent MP-AES 4100, which is associated with a large plasma volume and a higher input power.