Single vessel procedure for acid vapor partial digestion of bovine liver in a focused microwave: multielement determination by ICP-OES

An acid vapor partial digestion procedure for bovine liver is proposed using a focused microwave oven and a laboratory-made PTFE support. The support is equipped with three cups of approximately 4 ml volume each one and the cups were adapted to the glass reaction vessel of the microwave oven. A mixture containing HNO3 plus H2SO4 is heated to 120 °C to generate acid vapor. Bovine liver (50–90 mg) were directly weighed into the cups followed by addition of a mixture containing NaClO+H2O2. Samples were exposed to acid vapor during 15–25 min and then diluted with distilled and deionized water to final masses of 3.0 g. Recoveries of Al, Ca, Cu, Fe, Mg, Mn, and Zn were evaluated using an ICP-OES with axially-viewed configuration. The effects of both particle sizes and acid vapor exposure time were evaluated and recoveries of most elements were quantitative when using 25 min of heating and 50 mg of samples. Slightly better recoveries were reached using particles smaller than 44 μm, but this effect was mainly observed for hardly extracted elements such as Al and Fe.