Application Note

Fast Digestion Analysis of Lead and Cadmium in Rice Using Graphite Furnace Atomic Absorption


Lead (Pb) and cadmium (Cd) are common pollutants in grains and are extremely toxic. Pb is harmful to human organs even at trace levels, and once it accumulates in the body, it causes inhibition of hemoglobin formation and neurological disorders. Cd is even classified as human carcinogen [Group 1 - according to International Agency for Research on Cancer]. It is reported that Cd leads to severe kidney problems which can be fatal and is also associated with brittle bones and liver problems. Rice, as the most widely consumed cereal grain in Asia/China, can quickly pick up Pb and Cd from toxins, pesticides and fertilizers in the soil, thereby endangering the health of millions of people through their diet. Therefore, it is extremely important to develop a simple, reliable method to monitor the levels of Pb and Cd in rice. According to Chinese national standard GB 2715-2016 Hygienic Standard for Grain, the maximum concentrations of Pb or Cd in grains must be below 0.2 mg/kg; the allowable level in the European Union is the same [EC 1881/2006]. The official technique for the determination of heavy metals in both cases is graphite furnace atomic absorption spectroscopy (GFAAS, GB/T 5009. 12-2017, GB/T 5009-2017. 15 and EN 14083:2003). Samples can be pretreated using various methods, including microwave digestion, hot block digestion, dry ashing, and hot plate digestion. It is found that these conventional digestion procedures are always complicated and time-consuming (two-four hours or even longer). Plus, conventional sample preparation techniques require large quantities of corrosive and oxidizing reagents, increasing the chance for contamination which could lead to inaccurate results. Special PTFE vessels are needed for microwave digestion; however, reusable utensils might also cause cross contamination.