GF-AAS Determination of Lead in Preparations of Vitamin B₁₂

GF-AAS was applied to the determination of lead in preparations of vitamin B12 (e.g. healthcare food, feed and etc.). The sample was digested with conc. HNO3 and H2O2 in a pressure-vessel and heated in an electric oven with gradual temperature elevation from 60 ℃ to 160 ℃ for definite time-intervals. The solution obtained was evaporated to 0.5 mL and then diluted to 10 mL, which was used for determination of lead under the prescribed working condition of the instrument. Pyrolytic coated platform graphite tube was used and ashing was performed under the mode of gradient temperature elevations at 350 ℃ for 5 s and at 550 ℃ for 2 s. The atomization was carried out at the temperature of 1 700 ℃. Detection limit (3S/N) of the method was found to be 0.1 ng. Recovery and precision was tested at the concentration level of 20.0 μg·L-1 for 8 determinations, giving results of av. recovery of 100.2% and RSD of 0.39%.