ABSTRACT Miniaturization has been a trend in the instrumentation of chemical analyzes. The interest in miniaturization stems from the perceived benefits of faster, easier, less expensive and less wasteful analyzes than the tradition analyses. Thus, this work proposes a miniaturization of photocatalytic tests using a microplate reader for the analysis of several results, using only microliters of solution. The present work investigates the heterogeneous photocatalysis of the eosin yellow, acid yellow 73 and basic yellow 2 dyes, in the presence of zinc oxide (ZnO) and titanium dioxide (TiO2) catalysts, under irradiation in the visible light and ultraviolet light. Dye degradation was evaluated using a microplate reader (Elisa Polaris®), a photometric device that performs colorimetric readings in the 0-3 absorbance (ABS) range at wavelengths of 405, 450, 492 and 630 nm. The kinetic study was performed using the Langmuir-Hinshelwood law. It was verified that the degradation rates were higher than 90% over a period of 120 minutes for all the studied systems, especially the system composed of acid yellow dye 73 and the ZnO catalyst, which reached a degradation of 96.23% in 120 minutes.

A ocorrência de aflatoxinas B1 (AFB1), B2 (AFB2), G1 (AFG1) e G2 (AFG2), ocratoxina A (OA) e zearalenona (ZEA) foi avaliada em 121 amostras de alimentos à base de milho, que foram coletadas no comércio da cidade de Maringá, PR, Brasil, entre os meses de Janeiro/2002 a Fevereiro/2003. A cromatografia em camada delgada foi empregada para a determinação das micotoxinas. As médias das recuperações foram 106,6%, 109,4%, 106,6%, 109,4%, 101,8% e 101,7% para AFB1, AFB2, AFG1, AFG2, OA e ZEA, respectivamente. Três amostras (2,5%) foram positivas para AFB1 (8 a 59 µg/kg), duas (1,7%) para AFB2 (2,4 µg/kg), uma (0,8%) para OA (64 µg/kg) e uma (0,8%) para ZEA (448 µg/kg). A maior freqüência de amostras positivas e também a mais alta concentração de AFB1 foi encontrada nas amostras de pipoca (8,3%, 59 µg/kg). Os dados demonstraram uma baixa freqüência de micotoxinas em produtos à base de milho comercializados em Maringá, mas a Ingestão Diária Provável Média (IDP M) de AFB1 foi alta nos produtos analisados. Portanto, torna-se necessário a realização de uma vigilância ativa destas micotoxinas nestes produtos alimentícios, a fim de proporcionar segurança à saúde da população brasileira.

The occurrence of aflatoxins B1 (AFB1), B2 (AFB2 ), G1 (AFG1 ) and G2 (AFG2 ), ochratoxin A (OA) and zearalenone (ZEA) was evaluated in 121 maize-based food samples collected in the commerce of Maringá City, Paraná State, Brazil. The study was carried out between January 2002 and February 2003. Thin-layer chromatographic method was used to determine the mycotoxins. The recovery averages were 106.6%, 109.4%, 106.6%, 109.4%, 101.8% and 101.7% to AFB1, AFB2, AFG1, AFG2, OA and ZEA, respectively. Three samples (2.5%) were positive to AFB1 (8 to 59 µg/kg), two (1.7%) to AFB2 (2.4 µg/kg), one (0.8%) to OA (64 µg/kg) and one (0.8%) to ZEA (448 µg/kg). The greater frequency of positive samples and also the highest concentration of AFB1 were found in popcorn samples (8.3%, 59 µg/kg). The data showed a low frequency of mycotoxins in products based on maize traded in Maringá, but the Probable Average Daily Intake (PDI) of AFB1 in them was high. Therefore, it is necessary to accomplish an active vigilance of these mycotoxins in such food products in order to provide safety to Brazilian people health.