Determination of Lead, Cadmium, Arsenic and Nickel in Atmospheric Particulate Matter by Simultaneous Multi-Element Electrothermal Atomic Absorption Spectrometry

Abstract

A simple method for the determination of lead, cadmium, arsenic and nickel in atmospheric particulates by simultaneous multi-element Electrothermal Atomic Absorption Spectrometry has been developed. Due to the high concentrations of Pb and low concentrations of Cd, As and Ni found in particulate matter, lead was monitored at 261.4 nm and the other analytes at the usual wavelengths. Two approaches have been compared using aqueous standard solutions and acid extracts of particulate matter samples. First, a fast electrothermal programme, without chemical modifier, and a short pyrolysis step at 500°C for 10 s, has been developed. The omission of the pyrolysis step was not possible, because strong interference on arsenic was observed. The characteristic masses determined with this approach were 2.10 ng for Pb, 2.0 pg for Cd, 35.8 pg for As and 27.5 pg for Ni. The corresponding detection limits were 4.2 μg l−1 (Pb), 0.025 μg l−1 (Cd), 0.42 μg l−1 (As) and 1.5 μg l−1 (Ni), respectively. The second approach utilized the addition of Pd/Mg modifier (5 μg + 5 μg). The pyrolysis temperature (Tpyr) could be raised up to 650°C. The characteristic masses were 1.40 ng (Pb), 2.2 pg (Cd), 37.3 pg (As) and 27.9 pg (Ni). In the presence of Pd/Mg modifier the limits of detection were 4.3 μg l−1 (Pb), 0.020 μg l−1 (Cd), 0.26 μg l−1 (As) and 0.97 μg l−1 (Ni), respectively. These two approaches were applied in the determination of Pb, Cd, As and Ni in atmospheric particulates. Matrix matched calibration was used in order to achieve accurate and precise results. The calculated recoveries, in the absence of chemical modifiers, were 128% for Pb, 124% for Cd, 108% for As and 110% for Ni. The calculated recoveries were consistently better in the presence of the mixed Pd/Mg modifier: 101% (Pb), 99.7% (Cd), 103% (As) and 102% (Ni), respectively.