PERFIL ELEMENTAR DE AMOSTRAS DE MEL DE ABELHA SEM FERRÃO

Abstract

The stingless bees (SB) honey, a species native to Brazil, is a product used for different purposes due to its composition. It is worth mentioning the presence of metallic species, which can have a nutritional or toxic effect, depending on the amount ingested or the metal present, in addition to the possibility of being used as an environmental bio-indicator. The objective of this work was to develop a fast method for determining the metals Fe, Mn, Mg and Ca in SB honey by F AAS. The performance of the proposed analytical method was evaluated by comparing three slurry sampling procedures with microwave assisted digestion. For all procedures, 1.0 g of honey was used. Method A was performed using HNO3 (0.1 mol L-1); method B, HNO3 (0.2 mol L-1) and H2O2 (3%, w/v); and method C, only ultrapure water. Determinations of Fe, Mn, Ca and Mg were performed using Flame Atomic Absorption Spectrometry (F AAS). In this study, the highest metal extraction rates were observed for methods A and B, with percentages greater than 80% for all metals evaluated, while method C showed adequate extraction only for Mg. Method B was chosen, due to the higher extraction rates obtained for all metals through the tests performed. After choosing the most appropriate method, univariate optimization was performed, evaluating the honey mass from 0.5 to 2.0 g, the HNO3 concentration from 0.1 to 0.9 mol L-1, the concentration of H2O2 from 1 to 9% (w/v) and the ultrasonic stirring time of 5 to 20 minutes. The optimum conditions defined for the metals were: 1.0 g of honey, HNO3 (1.4 mol L-1), H2O2 (1.0%, w/v) and 5 minutes of ultrasonic stirring for Fe, Mn and Mg; and 2.5 g of honey, HNO3 (0.2 mol L-1), H2O2 (3.0%, w/v) and 10 minutes of ultrasonic agitation for Ca. The validation of the optimized condition was performed by evaluating the detection limits and quantification, linearity, precision and accuracy. During the validation of the proposed analytical method, the external standard analytical curve showed adequate linearity in the determination of the metals Fe, Mn, Mg and Ca. The limits of detection and quantification obtained were between 0.2 - 4.3 μg g-1, being considered low and adequate, according to the technique and methodology used. The precision of the method showed Relative Standard Deviation (RSD) values below 10% for intra- and inter-day measurements, and Horrat values between 0.5 (Fe) - 1.2 (Ca), both of which were within the criteria of acceptability recommended by regulatory bodies. For accuracy, comparing the proposed method with dry digestion, values between 86.5% (Ca) and 96.8% (Mg) were found, which are within the acceptability range for this parameter. After optimization and validation, the analytical method was applied to quantify 88 honey samples from different regions of Brazil. It was possible to quantify Fe in 88.6% of the samples in which the concentrations varied from ND to 123.9 ± 1.5 μg g-1. It was possible to quantify Mn in 95.5% of the samples, varying its concentration of ND to 41.9 ± 4.7 μg g-1. For Mg and Ca, which are the most abundant minerals in honey, it was possible to quantify them in most samples, their concentrations ranged from 1.6 ± 0.3 to 351.5 ± 9.6 μg g-1 and < LD → 0.04 ± 0.01 to 363.8 ± 6.4 μg g-1, respectively. The order of concentration in the samples was Ca> Mg> Mn> Fe. The levels obtained in the present work are similar to the levels found in the literature for the species evaluated. The proposed analytical method proved to be an efficient resource in the quantification of Fe, Mn, Mg and Ca in honey, when compared to traditional sample digestion methods using F AAS, as it presented advantages in minimizing some unwanted factors, such as the reduction time and volume of reagents, in addition to proving to be adequate, since the results obtained in the validation of this method are within the acceptability criteria of national and international regulatory bodies. The quantification of the metals evaluated in a significant number of samples can provide relevant information about the regions where honey is grown and the species of SB. Through the analysis of main components it was verified that the honey of the SB analyzed in the present study, have higher contents of metals, evaluated, than the honey of the species Apis mellifera from Brazil and other countries, as well as the honey of SB from other Brazilian states.