The sensitive determination of Ag, Pb and Tl as well as reduction of spectral interferences in a hanging drop cathode atmospheric pressure glow discharge excitation microsource equipped with a Dove prism system

Abstract

The application of hanging drop cathode (HDC) atmospheric pressure glow discharge (APGD) coupled with a Dove prism (DP) as an efficient excitation microsource for optical emission spectrometry (OES) was evaluated in details. The design of experiment (DoE) approach was applied to optimize the operating conditions, i.e., the discharge current, the graphite tube diameter, and the HNO₃ concentration, of this excitation source. The effect of the addition of low molecular weight organic compounds (LMWOCs) on the intensity of the analytical lines of Ag, Ca, Cd, Hg, Mg, Mn, Pb and Tl was evaluated, and the most beneficial results were obtained for 8% (m/m) formic acid. Using a Dove prism, the 2-D spatial distribution profiles of the emission lines of the selected elements (Ag, Ca, Cd, Hg, Mg, Mn, Pb and Tl) and the background species (H, O I, O II, N₂, OH, and NO) were obtained. In the developed system, the enhancement of the Ag, Pb and Tl atomic emission lines was the most spectacular and resulted in the improved limits of detection (LODs) of these elements, being 0.54, 14 and 2.2 μg L⁻¹, respectively. For this reason, this method was used for the sensitive determination of these analytes. The trueness and the precision of the developed method were verified by the analysis of a certified reference material (CRM) of tea leaves (INCT-TL-1).