Investigação de Novas Estratégias de Preparo de Amostras Orgânicas Auxiliado por Radiação Infravermelha

Abstract

In this work it was investigated the use of infrared radiation as heating source in the preparation of organic samples aiming the determination of trace elements by ICP OES. The strategies were developed in order to solubilize and / or digest larger masses of samples. Thus, three strategies were studied: 1) IR-MW system which combines the use of infrared radiation and microwave through a previous digestion with infrared radiation and subsequent digestion in the oven microwave cavity; 2) partial digestion using only infrared radiation (IR); 3) partial digestion using infrared radiation and vanadium pentoxide (IR with V2O5) as auxiliary oxidizing reagent. Various procedures were studied and the efficiencies were evaluated by the determination of macro-and microelements (Al, Fe, Cu, Mn, Zn, Se, Cd, Ni, Pb, Ca, K, Mg, Na, and P) in milk samples by ICP OES. The IR-MW system allowed the digestion of sample masses of up to 1 g, to obtain good precision for most of the elements determined. For the IR-MW A procedure the accuracy was confirmed with certified material of whole milk powder NIST 8435. For the IR-MW B and C procedures were obtained recovery rates varied depending upon the element and the sample. Strategies IR and IR with V2O5 allowed the partial digestion of 2 g of sample. The precision and accuracy of these procedures varied according to the element and the sample. However, the determination of some elements was only possible using these strategies, for instance, the detection of Mn (0.30 ± 0.01 µg g-1 by IR; 0.35 ± 0.01 µg g-1 by IR with V2O5) in the goat whole milk powder sample of and Mn (1.63 ± 0.02 µg g-1 by IR; 1.78 ± 0.06 µg g-1 by IR with V2O5) in the non-fat milk powder not enriched sample. The use of V2O5 was essential in the quantification of some elements such as Fe (0.54 ± 0.13 µg g-1) in goat milk powder samples. In general, the determination of trace elements by ICP OES is only possible using larger amounts of sample, depending on the element and its content in the sample. The use of infrared radiation to accomplish the digestion of larger masses of samples is an alternative to using only laboratory microwave oven cavity.