Determination of Pb in road dust by high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

The ever-increasing vehicle traffic circulation around the world has also caused an increase of environmental pollution. In addition to the fuel combustion, wear of vehicle components and road surface are sources of particles released to the atmosphere. In this context, the determination of traffic-related elements (TREs), especially potentially toxic metals, in environmental samples such as road dust has become of growing concern in recent years mainly due to the toxicity and persistence of these elements in the environment [1,2]. In this work, we investigated the capabilities of direct solid sample analysis by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS SS-GF AAS) for the determination of Pb in road dust samples. Samples were collected in the megacity of Buenos Aires and then fractionated by particle size. The fraction between 37 and 50 µm was analyzed in this study. Due to the high Pb content in the samples, the main analytical line of Pb (217.001 nm) was not evaluated, thus alternative lines were investigated in order to reduce the sensitivity. The wavelength at 261.418 nm (2.1% relative sensitivity) was finally selected. For optimization of the GF AAS program, pyrolysis and atomization temperature curves were established with the road dust sample M-112C using 10 μL of a 0.1% Pd + 0.06% Mg + 0.05% Triton X-100 solution as chemical modifier. Calibration was achieved using aqueous standards. The figures of merit were: characteristic mass of 1.3 ng, and limit of detection and quantification of 0.85 and 2.8 mg kg−1, respectively, based on a sample mass of 0.8 mg. Relative standard deviation values were <10% (n=5), which can be considered acceptable for direct analysis. The accuracy of the method was verified using two certified reference materials, road dust (BCR-723) and soil (NIST SRM 2586). The results were statistically in agreement with the certified values at a 95% confidence level. The concentration of Pb in the samples varied between 195 and 305 mg kg-1.