Infrared Radiation Applied as a Heating Source in Milk Sample Preparation for the Determination of Trace Elements by Inductively Coupled Plasma-Optical Emission Spectroscopy

The use of infrared (IR) radiation as a heating source for milk sample preparation in trace element analysis by inductively coupled plasma optical emission spectroscopy (ICP-OES) was investigated. Three strategies were studied: 1) a system that combined IR and microwave radiation (IR-MW); 2) partial digestion using only IR radiation (IR); and 3) partial digestion using IR radiation and vanadium pentoxide as a catalyst (IR-V2O5). Accuracy varied according to the element determined. The procedure using only IR radiation presented 15.1 +/- 0.3 mg g(-1) for Ca, 0.76 +/- 0.03 mu g g(-1) for Cu, 217 +/- 2 mu g g(-1) for Fe, 14.8 +/- 0.7 mg g(-1) for K, 1.17 +/- 0.03 mg g(-1) for Mg, 4.41 +/- 0.08 mg g(-1) for Na, 16.2 +/- 0.1 mg g(-1) for P and 30.5 +/- 0.6 mu g g(-1) for Zn in non-fat milk. The use of IR radiation for sample preparation in trace element analysis is an easy to implement and a low-cost alternative for laboratories of food analysis that do not have a microwave available.