Comprehensive evaluation of matrix effect in the detection of Zn, Cd, Ni, Cu, Cr and Pb by solution cathode glow discharge optical emission spectrometry

Abstract

Herein, the effect of different salt matrices on the signals of Zn, Cd, Ni, Cu, Cr, and Pb using solution cathode glow discharge optical emission spectrometry (SCGD-OES), was discussed at length. The cation interference test covered sodium, potassium, magnesium and calcium ions, while the anion interference test covered chloride and sulfate ions. Overall, the order of interference levels for the four cations was: Na+≈K+>Mg2+≈Ca2+. The emission of most elements was inhibited at Na+/K+/Mg2+/Ca2+ concentration exceeding 200 mg L-1. The impact of the two anions is not measurably different and almost no interference occurred when anion content reaching 200 mg L-1. The spectral interference caused by Na+ and K+ was also much greater than that of Mg2+ and Ca2+, which was reflected in the diminution of spectral bands of the two main molecules (OH and N2). The role of formic acid (HCOOH) has been reassessed at a salinity of 200 mg L-1 Na+. HCOOH was found to play a positive role on volatile species forming metals such as Pb, regardless of the presence of sodium salts. For elements (Cr) that are hard to evaporate and stimulate, HCOOH exhibited a strong inhibitory effect, possibly due to exacerbating the deterioration of the excitation state. For other transition metal elements in the fourth period, e.g., Zn, HCOOH demonstrated minor effects.