An atomic absorption spectrometer (Unicam 929 A) equipped with deuterium background correction and a Shimadzu
AA 6701 spectrometer equipped with a GFA-6500 graphite furnace atomiser were used for AAS measurements. A magnesium hollow-cathode lamp (Photron) was operated at 3 mA. The magnesium absorbance was measured at 285.2 nm with a 0.5 nm spectral bandwidth. Pyrolytically coated graphite cuvettes and argon gas were used in electrothermal AAS (ET-AAS) measurements. An air–acetylene flame was used for the flame AAS (FAAS) measurement