Internal standardization in axially viewed inductively coupled plasma optical emission spectrometry (ICP OES) combined with pneumatic nebulization and aerosol desolvation

Abstract

Internal standardization using axially viewed inductively coupled plasma optical emission spectrometry (ICP OES) combined with pneumatic nebulization/aerosol desolvation was evaluated in the present study. The sample and internal standard (IS) solutions were mixed on-line. Spectral lines of In, Y, Ga and Ar were evaluated for internal standardization under robust plasma conditions to overcome matrix effects on Ba, Cd, Co, Cr, Zn, Pb, Sr, Mn, Cu, Ni and V quantification in digests of plant materials. In(II)230.606 nm was only effective for Cd and Pb whereas Y(II)371.029 nm or Ga(I)417.206 nm or Ga(I)294.364 nm were effective for the other investigated elements. Argon was not effective, suggesting that matrix effects were related to aerosol generation and its transport to the ICP. By using internal standardization accurate results were obtained for certified reference samples of plant materials and the relative standard deviation (RSD) was lower than 1% even for solutions with high acid concentration. The limits of quantification (LOQ) of Cr(I)357.869, Cr(II)267.716, Cu(I)327.393, Cu(II)224.700, Cd(I)228.802, Cd(II)214.440, Pb(I)217.000, Pb(II)220.353, Zn(I)213.857, Zn(II)206.200, Sr(II)407.771, Ba(II)233.527, V(II)292.464, Mn(II)257.610, Ni(II)232.003 and Co(II)228.616 nm were 0.070, 0.041, 0.065, 0.094, 0.033, 0.056, 1.33, 0.45, 0.065, 0.10, 0.005, 0.20, 0.12, 0.015, 0.10 and 0.047 μg g⁻¹, respectively. It was concluded that the method is feasible for routine applications.