Estratégias analíticas utilizando ferramentas quimiométricas para análise de alimentos de consumo humano e de animais empregando técnicas espectrométricas

Abstract

In this work three studies were developed involving strategies for food analysis for determination of inorganic constituents in animal feeds and sugarcane juice samples, as well as, the chemical speciation analysis of As, Sb and Se of dried fruits using atomic spectrometry. In the first work, experimental designs were applied to optimize the conditions of microwave-assisted sample decomposition and operational of spectrometer for animal feeds analysis. Inductively coupled plasma (ICP) based methods were used to determine the concentrations of 23 elements in feed for ornamental and human fishes, ruminants, wild birds, rabbits and equines. The limits of quantification obtained ranged from 0.02 mg kg-1 (Cd) to 76 mg kg-1 (Al). The reliability to the methods was confirmed by the analysis of certified reference material (CRM) of oyster tissue (NIST 1566b) and tea (NCS DC 73351). The concentrations obtained ranged between 0.038 mg kg-1 (Sb) and 3.37% (Ca) for ornamental fishes, <LoQ (Ba) and 2.0% (Ca), <LoQ (Cd, Pb and Sb) and 2.0% (Ca) for rabbits, <LoQ (Cd, Pb, Sb and Se) and 2,53% (Ca) for wild birds, 0.034 mg kg-1 (Sb) and 2.10% (Na) for equines and, <LoQ (Se) and 14% (Ca) for ruminants, all of which are in accordance with Brazilian and American legislation. In the second work, a multivariate optimization of a sample preparation procedure as slurry was used to determine Ca, Cu, Fe, K and Mg in sugarcane juice samples by inductively coupled plasma optical emission spectrometry (ICP OES). The fractional factorial and Doehlert designs were applied to optimize the variables: HNO3 concentration, H2O2 volume, sonication time, nebulizer gas flow and radiofrequency power for direct analysis of the sample as slurry. The procedure was validated by comparing digestion with addition and recovery tests. The proposed analytical method was applied to the analysis of fourteen samples of sugarcane juice marketed in Aracaju, Sergipe, Brazil. The mean concentrations (in mg L-1) of 108 (Ca), 0.51 (Cu), 6.40 (Fe), 470 (K) and 114 (Mg) were obtained. The methodology presented offers a simple, fast, easy and efficient of sample preparation form simultaneous determination in sugarcane juice by ICP OES. Finally, in the third work the chemical speciation analysis of As, Sb and Se in dried fruit samples was performed using multi-syringe flow injection analysis hydride generation atomic fluorescence spectrometry (MSFIA-HG-AFS). For As and Sb determinations, the concentrations of NaBH4, KI and HCl were evaluated as factors. For Se, only concentrations of NaBH4 and HCl were evaluated. The two optimizations were performed through Doehlert designs, having the intensities of As, Sb and Se as response. Limits of quantification ranged from 0.34 (Sb total) to 15 ng g-1 (As total). The accuracy and precision of the analytical methods were evaluated through the analysis of certified reference material and addition and recovery tests. The analytical methods were applied to nine dried fruit samples, and the highest concentrations (in ng g-1) were 8.2 ± 0.6 for Sb(III), 14.0 ± 1.2 for Sb(V), 102.5 ± 7.4 for Se(IV) and 90.5± 9.8 for Se(VI). The As(III) and As(V) species obtained concentrations below the LoQ for all samples. In this work, analytical methods for the determination of total concentrations of essential and potentially toxic elements in food and feed, have been satisfactory and can be used for routine analysis to evaluate the chemical composition of foods.