Study and reduction of matrix effects in flowing liquid anode - Atmospheric pressure glow discharge - Optical...

The effect of different interfering elements, i.e., Na, K, Mg, Ca, Al, Cu, Fe, Mn, Ni, and Zn, on the analytical performance of flowing liquid anode atmospheric pressure glow discharge optical emission spectrometry (FLA-APGD OES) was extensively studied. In the presence of interfering ions, the emission from analytes was suppressed by ∼10% in the case of Hg and Tl, ∼20% for Cd and Ag, and up to ∼80% for Zn and Pb. This study revealed that interfering elements did not affect the atomization/excitation conditions, and the reason for the observed decrease in analytical response was the impaired efficiency of analytes transport from liquid to plasma phase. To reduce matrix effects, the use of different masking agents capable of complexing the interfering ions, e.g., organic acids, crown ethers, chelating agents, and other compounds, was investigated. FLA-APGD appeared to be quite susceptible to the presence of masking agents and only their small amounts could be added (limiting the effectiveness of this approach). Despite this, it was possible to significantly reduce the matrix effects originating from transition metals and alkali/alkaline earth metals. Based on the results presented herein, different sample treatment procedures, aimed at the minimization of matrix effects in microplasma excitation sources, can be developed. As an example, a method for the determination of trace amounts of Zn and Pb in the Fe-rich matrix has been shown. By the use of the selected masking agents, the recovery of Zn and Pb was improved 5.6-fold (from 10.4 to 57.8%) and 2.8-fold (from 13.6 to 38.0%), respectively. Despite the presence of Fe-rich matrix, the detection limits of Zn and Pb were quite low (0.1 and 0.8 μg L^-1, respectively) and they were apparently lower than offered by ICP OES.