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