Multi-element Analysis of Food by Microwave Digestion and Inductively Coupled Plasma-Atomic Emission Spectrometry

A microwave digestion procedure for multi-elemental analysis of food was developed using one program to digest a variety of food matrices at the same time. A single program was enabled by an analytical portion mass based on the food's energy content calculated from macronutrient data (fat, protein and carbohydrate). The procedure allows a maximum mass to be analyzed for each food matrix without adjustment of the microwave digestion program to compensate for the variable reactivity of food matrices. Inductively coupled plasma-atomic emission spectrometry with ultrasonic nebulization was used to determine aluminum, arsenic, boron, barium, calcium, cadmium, cobalt, chromium, copper, iron, potassium, magnesium, manganese, molybdenum, sodium, nickel, phosphorus, lead, selenium, strontium, thallium, vanadium, and zinc. Method validation was performed on seven certified reference materials and 20 foods. Element fortification recovery of foods was acceptable (88–113%) and a majority of available comparisons to reference materials indicated agreement except for aluminum, chromium, and selenium.