Microwave-induced combustion for further determination of potentially toxic elements in honey by ICP-MS.

Microwave-induced combustion (MIC) was proposed in this study for honey decomposition aiming for As, Cd, Hg, and Pb determination by inductively coupled plasma mass spectrometry (ICP-MS). Sample mass (up to 1.0 g), absorbing solution (0.5 to 14.4 mol L-1 HNO3, and H2O), heating program, and combustion aids were evaluated. The Eurachem guidelines were used for method validation. The proposed method enabled combustion of a high sample mass (0.8 g of honey, with 0.4 g of microcrystalline cellulose and 100 µL of 6 mol L-1 NH4NO3) using 6 mL of an absorbing solution consisting of 1 mol L-1 HNO3, which resulted in low residual carbon in solution (< 25 mg L-1). Honey samples from different geographical origins were analyzed. Results showed no significant difference in comparison to other two microwave decomposition methods, based on microwave-assisted wet digestion with single reaction chamber (MAWD-SRC) and microwave-assisted wet digestion (MAWD). Standard addition experiments resulted in recoveries higher than 98%. The limits of detection ranged from 1.10 (As) to 4.60 ng g-1 (Pb). In addition to using only diluted reagents and resulting in digests virtually free of interferences, the proposed method was faster (< 30 min) than most of those presented in the literature.

Ilex Paraguariensis exposition to As and Cd in a closed soilless system.

The exposition of mate (Ilex Paraguariensis A. St.-Hil.) to As and Cd was investigated in plants derived from young mini-cuttings. Mate plants were cultivated in a closed soilless system, composed of coarse sand as substrate and flood fertirrigation. Plantlets were fertirrigated with nutritive solution and As and Cd solutions were added to the nutritive solution in the final concentration of 8 and 17 mg L-1 (As) and of 17 and 33 mg L-1 (Cd) during 14 days. Results show that stem diameter and Dickson quality index (DQI) variables could not be used as a potential indicator of accumulation of As and Cd. The shoot height, number of leaves and chlorophyll index are variables easy and quick to measure and they can be used as parameters to evaluate the stress caused in mate plants cultivation in a closed soilless system. The highest concentration of As and Cd was in roots of plants. Beyond the roots, As and Cd also can be translocated to the leaves achieving high concentrations. In addition, leaves from the treated mate plants were submitted to a hot infusion extraction in order to simulate the traditional beverage and As and Cd were determined in the infusion. Regarding to the infusion procedure, considerable As and Cd amounts were extracted from the leaves leading to conclude that this way of consumption can be an important source of toxic elements for the human diet.