Screening Method for Determination of High Levels of Cadmium, Lead, and Copper in Foods by Polarized Zeeman Atomic Absorption Spectrometry Using Discrete Nebulization Technique

Abstract

A screening method for determination of cadmium, lead, and copper in foods was developed. The sample (1-3 g) is digested with HNO3-H2SO4-HClO4 in a centrifuge tube attached to a straight glass tube that prevents loss of HNO3 by volatilization. After digestion, potassium iodide, H2SO4, and MIBK (4-methyl 2-pentanone) are added, and the metals are extracted with MIBK as metal iodides. The MIBK solution is injected and the metals are determined by flame polarized Zeeman atomic absorption spectrometry using a discrete nebulization technique. Recoveries of metals from fortified milk powder, unpolished rice, fish, beef, peanut butter, apple, and cabbage were satisfactory. The analytical results for NBS Oyster Tissue and NIES Pepperbush, Chlorella, and Mussel agreed with certified or reference values except lead in Pepperbush. The limits of quantitation for cadmium, lead, and copper were 0.01, 0.09, and 0.02 ppm, respectively. This method is simple and safe for routine analysis of high levels of cadmium, lead, and copper in foods.