Determination of metals in foodstuffs by atomic absorption spectrophotometry after dry ashing: NMKL interlaboratory study of lead, cadmium, zinc, copper, iron, chromium, and nickel.

An interlaboratory study of a method for determination of lead, cadmium, zinc, copper, iron, chromium, and nickel in foodstuffs by atomic absorption spectrophotometry (AAS) after dry ashing at 450 degrees C was conducted in 16 laboratories. The study was preceded by a practice round of familiarization samples and another round in which solutions were distributed and the metals were determined directly by AAS. The study included 5 different foods (liver paste, apple sauce, minced fish, wheat bran, and milk powder) and 2 composite diets. A single analysis was carried out on each sample. Suitable sample combinations were used as split level combinations for determination of the repeatability standard deviation. The relative reproducibility standard deviation for each of the elements ranged as follows: lead, 74-18% at 0.025-0.28 mg/kg; cadmium, 80-11% (0.002-0.51 mg/kg); zinc, 12-7% (44-72 mg/kg); copper, 47-10% (0.48-41 mg/kg); iron, 35-9% (2-228 mg/kg); chromium, 48-21% (0.008-0.22 mg/kg); nickel, 64-39% (0.025-0.39 mg/kg).