In this work, the photochemical vapor generation (PVG) coupled with atomic absorption spectrometry and a pre-concentration step with an Au column was used for the determination of Hg in biological samples and ethanol fuel. PVG with pre-concentration showed an up to 250-fold higher sensitivity compared to the approach without pre-concentration. The accuracy of analysis of biological samples was evaluated using certified reference materials (fish tissues), while for ethanol fuel samples, recovery tests were employed (91%). Analytical curves were linear (R > 0.99) in the studied range of 2.5 to 10 µg L-1 for conventional PVG and 0.2 to 0.5 µg L-1 for PVG with the pre-concentration step. For the last, the limits of detection reached for biological samples and ethanol fuel were 0.02 and 0.01 µg L-1, respectively. The systems presented are simple, sensitive and safe for the control of low Hg concentrations in different samples. However, only the system using pre-concentration with an Au column was capable of obtaining the reproduced signals of Hg in low concentrations of the order of 0.2 µg L-1.

No presente trabalho foi avaliada a atividade inseticida de extratos de limbos foliares de Tapirira guianensis Aubl. (Anacardiaceae), Attalea phalerata (Mart. ex Spreng.) Burret (Arecaceae), Eugenia uniflora L. (Myrtaceae) e Gomphrena elegans Mart. (Amaranthaceae) e de caules de Myracrodruon urundeuva Allemão (Anacardiaceae). Foram testados quatro extratos e 18 frações, com diferentes polaridades. Dez gramas de grãos de trigo foram pulverizados com 1 mL de cada extrato a 10% (p/v). Após a evaporação do solvente a 38 ºC, os grãos foram acondicionados em recipientes juntamente com 20 indivíduos adultos de Sitophilus zeamais não sexados, com 10 a 20 dias de idade. As avaliações foram feitas no quinto e no décimo dia, contando-se o número de insetos mortos e descartando-os. Os extratos foliares de G. elegans ocasionaram mortalidade de 27% a 60% até o quinto dia, enquanto os demais extratos testados, quando ativos, não ultrapassaram a faixa de 20% de mortalidade no mesmo período. No décimo dia, os extratos mais ativos foram o proveniente de A. phalerata (hexânico, 36,5%) e todos os de G. elegans (52% a 80,5%), enquanto os demais extratos causaram até 30% de mortalidade.

This paper reports on an evaluation of the insecticidal activity of extracts prepared from leaves of Tapirira guianensis Aubl. (Anacardiaceae), Attalea phalerata (Mart. ex Spreng.) Burret (Arecaceae), Eugenia uniflora L. (Myrtaceae), and Gomphrena elegans Mart. (Amaranthaceae) and from stems of Myracrodruon urundeuva Allemão (Anacardiaceae). Four extracts and 18 fractions with a range of polarities were tested. Ten-gram batches of wheat grains were each nebulized with 1 mL of a separate extract at 10% w/v. After solvent evaporation at 38 ºC, the grains were placed into flasks along with 20 unsexed 10- to 20-day old adult individuals of Sitophilus zeamais. The assessment was carried out on the fifth and tenth day by counting and discarding the dead insects. Leaf extracts of G. elegans showed an insecticidal effect ranging from 27% to 60% by the fifth day, whereas the effect of the remaining extracts tested (if active at all) did not exceed 20% in the same period. By the tenth day, the most active extracts were those of A. phalerata (hexanic, 36.5%) and all those of G. elegans (5280.5%), whereas the effect of the other extracts did not exceed 30%.