Evaluation of the Platinum Group Metals as Modifiers for Determination of Cd, Pb and Ni in Syrian Cow Milk by Graphite Furnace Atomic Absorption Spectrometry

Abstract

Cadmium, lead and nickel contents in Syrian trade marks cow milk (goody, milk man, buon giorno, Rihana and Al-faiha) were determined, by using atomic absorption spectrometry with a transversely heated graphite atomizer (THGA) and a self-reversal (SR) background correction system, after microwave digestion. The electrothermal behaviour of aqueous solution containing 3 μg L^-1 Cd, 50 μg L^-1 Pb and 50 μg L^-1 Ni in 0.2 % HNO₃ during pyrolysis and atomization steps was studied, without modifier and in modifier presence of 10 μg Pt, Ru, Ir, Rh and Pd. Palladium was selected as the optimum modifier with concentration range 1-5 μg for Cd and 1-10 μg for Pb and Ni. The pyrolysis and atomization temperatures in presence of Pd as modifier were fixed at 850 ºC and 1600 ºC for Cd, at 950 ºC and 2000 ºC for Pb and at 1550 ºC and 2300 ºC for Ni respectively. The characteristic masses (m₀) were 1.19 pg Cd, 27.75 pg Pb and 34.46 pg Ni. Limits of detection (LOD, 3s) were 0.037 μg L^-1 Cd, 1.06 μg L^-1 Pb and 2.04 μg L^-1 Ni. Analytical linear ranges were 0.25-5 μg L^-1 for Cd, 5-80 μg L^-1 for Pb and 25-100 μg L^-1 for Ni with the Pd modifier.