METHOD FOR DETERMINING PB IN FOOD SAMPLES OF VEGETAL ORIGIN BY FREEZE-DRYING, ULTRASONICALLY-ASSISTED EXTRACTION AND GRAPHITE FURNACE ATOMIC ABSORPTION ()

摘要

The invention relates to a method for determining Pb in food samples of plant origin. According to the invention, the method consists in drying an amount of 100 ... 200 mg of plant mixture sample by lyophilization at -40° C and 25 psi, for 6 h, subjecting it to ultrasound-assisted extraction in HCl solution, 0.5 mole/l, for 15 ... 20 min, at 60 ... 70° C, at a frequency of 35 kHz and a power of 400 W, after which the mixture is cooled, centrifuged at 4400 ... 4500 rpm for 10 min and the supernatant is separated for the Pb content determination analysis, using a graphite furnace atomic absorption spectrometer, the method having a detection limit of less than 0.05 μ g/Kg wet weight and a certified degree of recovery upon analysis of the reference material of 97%.