INFRARED GREEN SAMPLE PREPARATION FOR MULTIELEMENTAL ANALYSIS OF ANIMAL FEED BY MPAES

CORA JOFRE, F.; LARREGUI, D. N.; SOSA, A. P.; ROSSINI, A.; SAVIO M.

Caldas Novas

Congreso; 19° ENCONTRO NACIONAL DE QUÍMICA ANALÍTICA 7° CONGRESSO IBEROAMERICANO DE QUÍMICA ANALÍTICA; 2018

The employment of confined animals to increase production efficiency has grown the market for animal feed supplementation. Feeds for farm animals must contain suitable nutrients concentration,since its composition may affect animal health and its productivity. Thus, knowing essential and non-essential elements concentration in feed is of great importance. One of the main analytical chemistry challenges has been to overcome problems to bring samples into solutions, which should be compatible with the spectrochemical instrumental technique for inorganic trace analysis. Microwave induced plasma atomic emission spectrometry (MPAES) was selected in this work for multielemental determination, when comparing its rapid detection time along with the sample preparation, the latter is time consuming. So, sample preparation has become a bottleneck for the whole analytical procedure; it is a critical and essential step, especially forsamples with complex matrices. Sample decomposition methods using microwave radiation in closed systems have been commonly used; however, these methods are limited to small amounts of organic samples and the impossibility to digest samples with different characteristics in the same cycle. Therefore, a procedure for sample preparation of pigs animal feed using commercially available infrared (IR) radiation lamps was evaluated in this work as it could be extensively usedbased on its ability to promote fast heating solutions. Samples were dried and ground thoroughly, then, were exactly weighted into PTFE vessel with masses around 0.15 g. Subsequently 2 mL of HNO3 and 2 mL de H2O2 were added. Thesesuspensions were submitted to an infrared heating developed device for digestion. Efficient digestions were promoted for all samples. The digestion efficiency was evaluated by determining the dissolved carbon content, which was lower than 1%; residual acidity was also evaluated and was lower than 0.6 mol L-1. Aluminium, Ba, Ca, Cd, Co, Cu, Fe, K, P Mg, Mn, Na, Sr and Zn weredetermined by MPAES. The proposed sample preparation was validated by mineral supplement certified reference materials and by comparison with another analytical technique (ICPOES);analytical recoveries were between 80-120%. Detection limits were found in the range between 18.67 ug kg-1 (Ba) and 148 mg kg-1 (Fe), and accuracy (expressed in terms of relative standarddeviation, RSD) was better than 10%.The proposed method is simple and low-cost, allowing total samples digestion rich in organic compounds using small volumes of nitric acid. The main advantages are that it is in agreement with green analytical chemistry principles, minimizing the employed reagents amount, the residues generation and the sample manipulation.