Determination of Cd, Pb and Ni in Syrian Cow Milk by Graphite Furnace Atomic Absorption Spectrometry

Abstract

Graphite furnace atomic absorption spectrometry method was elaborated and applied for determining Cd, Pb and Ni in Syrian cow milk samples using the transversally heated graphite atomizer with integrated graphite platforms. The effects of several chemical modifiers, such as NH₄H₂PO₄, Mg(NO₃)₂, Zr, W, ascorbic acid and mixture of NH₄H₂PO₄ and Zr were studied to obtain optimal pyrolysis and atomization conditions for the studied analytes. The most efficient modifier was proved to be the mixture of NH₄H₂PO₄ and Zr, which gave the optimal pyrolysis and atomization temperatures: 900 and 1800 ºC, 1000 and 1900 ºC, 1500 and 2500 ºC respectively for Cd, Pb and Ni. The characteristic masses (m₀) were 1.29 pg Cd, 25.20 pg Pb and 33.13 pg Ni. Limits of detection (LOD, 3s) were 0.044 μg L^-1 Cd, 0.94 μg L^-1 Pb and 1.32 μg L^-1 Ni. Limits of quantification (LOQ, 10s) were 0.146 μg L^-1 Cd, 3.133 μg L^-1 Pb and 4.4 μg L^-1 Ni. The cow milk mean contents were to be 3.78 μg kg^-1 for Cd, 17.59 μg kg^-1 for Pb and 0.45 mg kg^-1 for Ni.