Determination of mercury in size fractionated road dust samples by flow injection-cold vapor-atomic absorption spectrometry

An investigation was carried out to explore the effect of citric, hydrochloric, oxalic and tartaric acids on mercury vapor generation in a flow injection system in conjunction with atomic absorption spectrometry detection (CV-AAS) for its determination in road dust samples. Samples were collected in Buenos Aires (Argentina) during two months at 15 sites grouped in five zones with different urban characteristics and traffic profile. They were sieved in four fractions (with the following particle diameter (d): A: d < 37 mu m, B: 37 < d < 50 mu m, C: 50 < d < 75 mu m, and D: 75 < d < 100 mu m) before Hg determination. The operating conditions (chemical and physical parameters) and the type and concentration of the acids studied (citric, hydrochloric, oxalic and tartaric) were assessed for the efficient generation of Hg. The interfering effect of metals and metalloids, present as minor and major concentrations in road dust, on Hg signal were evaluated using the four acids. Hydrochloric acid resulted to be the most convenient reaction medium in terms of sensitivity but a suitable control of interferences was not reached. For a complex matrix such as road dust, the best control of interferences was achieved when oxalic acid was tested, even when lower Hg signal was obtained in comparison with HCl. The detection limit (3 sigma criterion) turned out to be 0.3 ng g(-1). For checking accuracy, two certified reference materials were analyzed and results were in good agreement with certified values. Mercury concentrations in road dust ranged between 0.1 mu g g(-1) and 4.6 mu g g(-1) and the mean concentration value resulted to be 1.09 mu g g(-1). In the four fractions, Hg concentrations (mu g g(-1)) varied as follows: Fraction A (<0.0003-3.51); Fraction B (0.49-4.63); Fraction C (0.20-1.36) and Fraction D (0.16-1.88). The procedure is simple, rapid and robust. (c) 2012 Elsevier B.V. All rights reserved.