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.

Determination of toxic elements in yerba mate by ICP-MS after diluted acid digestion under O2 pressure.

In this work, a procedure allowing effective digestion of a high mass of yerba mate (up to 1500 mg) using diluted HNO3, in a system pressurized with oxygen, is proposed. Digests were suitable for direct analysis by ICP-MS, virtually free of interferences. Digestion was performed using 7 mol l-1 HNO3 and 8 bar O2. The digestion efficiency was better than 92% and digests presented a relatively low acidity (<10 mmol HNO3). The limit of quantification was 4.0, 1.0 and 1.0 ng g-1 for As, Cd and Pb, respectively. Under optimized conditions up to 1500 mg of sample were digested and no interferences were observed during analyses by ICP-MS, making this approach suitable for routine determination of As, Cd and Pb in yerba mate and also in agreement with the quality control requirements.