Determination of thirteen common elements in food samples by inductively coupled plasma atomic emission spectrometry: comparison of five digestion methods

Five sample digestion procedures were evaluated for the determination of Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, P, S, Sr, and Zn in food samples by inductively coupled plasma atomic emission spectrometry. The 5 procedures include dry ashing at 500 degrees C, wet digestion with HNO3-HClO4, microwave digestion with HNO3, microwave digestion with HNO3-H2O2, and microwave digestion with HNO3-H2O2-HF. For microwave digestion with HNO3-H2O2-HF, silicon (IV) oxide was used to eliminate the excess HF, making it possible to determine total Al, B, and other common elements accurately and simultaneously. Seven National Institute of Standards and Technology standard reference materials (SRMs) were analyzed to compare the recovery of 13 elements with above digestion procedures. The results demonstrated that the microwave digestion procedure with HNO3-H2O2-HF yielded the best recoveries for all 13 elements in the selected SRMs. The determined concentrations of most elements were close for all 3 microwave digestion procedures with the exception of Al in oyster tissue, bovine liver, and spinach. Notably, the wet digestion with HNO3-HClO4 is the simplest and the most effective procedure for the selected elements except Al and B. Although there are several concerns with the dry ashing procedure, it might be a preferable procedure for those analyses where only nonvolatile elements are to be determined and the concentrations of the elements are low.