The aim of this work was to investigate the copper electrode behavior in the voltammetric determination of glyphosate. The best conditions for this determination are phosphate buffer 0.05 mol L-1 and pH 7.3, and the peak potential is observed at 187 mV. LD and LQ values are 59 µg L-1 e 196 µg L-1, respectively. A water sample was analysed for glyphosate and identical results were obtained by using the analytical curve and the standard addition method. The comparison with a voltammetric method with Hg electrode, after a reaction with nitrite, showed quite concordant results for the analysis of the surface water sample. Therefore, the proposed method can be applied to direct determinations of the herbicide in waters, decreasing the time of analysis; besides, the method is in agreement with the "green chemistry" concept.

A very simple spectrophotometric method is described for resolving binary mixture of the food colorants Sunset Yellow (INS 110) and Tartrazine Yellow (INS 102) by using the first derivative spectra with measurements at zero-crossing wavelengths. Before the spectrophotometric measurements, the dyes were sorbed onto polyurethane foam and recovered in N,N-dimethilformamide. Commercial food products (gelatine and juice powder) were analysed by using the proposed method and the HPLC technique. The results are in very good agreement and the differences between the methods is not statistically important. Therefore, the first-order derivative spectrophotometric method is accurate, precise, reliable and could be applied to the routine analysis of food samples.

Algae constitute a large group of many different organisms, essentially aquatic and able to live in all systems giving them sufficient light and humidity. Some algae species have been used in the evaluation or in the bioremediation of aquatic systems. More recently algae have been suggested as interesting tools in the field of analytical chemistry. In this work the most important aspects related to the different uses of algae are presented with a brief discussion.

Arsênio total, As(III), As(V) e ácido dimetilarsínico (DMA) foram determinados seletivamente em águas naturais pela técnica da geração de hidretos - espectrometria de absorção atômica, em diferentes meios de redução. Para as amostras de água de rio investigadas os resultados mostraram ser arsenato a forma arsenical predominante. Os limites de detecção encontrados para As(III) (tampão citrato), As(III) + DMA (ácido acético ) e As(III) + As(V) (ácido clorídrico) foram, respectivamente, 0.6, 1.1 e 0.5 mg As L-1. O estudo da estabilidade das formas arsenicais em amostras de águas naturais revelou serem os próprios meios reacionais convenientes para uma preservação adequada das amostras.

Total arsenic, arsenite, arsinate and dimethylarsinic acid (DMA) were selectively determined in natural waters by hydride generation - atomic absorption spectrometry, using sodium tetrahydroborate(III) as reductant but in different reduction media. River water samples from the north region of Paraná State, Brazil, were analysed and showed arsenate as the principal arsenical form. Detection limits found for As(III) (citrate buffer), As(III) + DMA (acetic acid) and As(III) + As(V) (hydrochloric acid) were 0.6, 1.1 and 0.5 mg As L-1, respectively. Sample storage on the proper reaction media revealed to be a useful way to preserve the water sample.

A determinação seletiva de As(III), As(V) e ácido dimetilarsínico (DMA) foi estudada pela técnica da geração de hidretos - espectrometria de absorção atômica. Os meios de redução selecionados permitiram a determinação de As(III) na presença de tampão citrato (0,4 mol/L, pH4,4), As(III) + As(V) no meio HCl 6 mol/L, após uma pré-redução com iodeto de potássio, e As(III) + DMA em CH3COOH 0,12 mol/L. O teor de arsênio total pode ser determinado no meio HCl 6 mol/L, após ser efetuada a pré-redução das formas As(V) e DMA com iodeto de potássio e cloreto estanoso. Os efeitos de interferência causados por diferentes íons metálicos foram, também, avaliados.

Hydride generation - atomic absorption spectrometry, using sodium tetrahydroborate(III) as a reductant, was used to form arsines selectively from inorganic arsenic(III) and arsenic(V), and dimethylarsinic acid (DMA). The selected reaction media allowed the rapid determination of arsenic(III) alone (citrate buffer 0.4 mol/L, pH 4.4), arsenic(III) + arsenic(V) (HCl 6 mol/L, after pre-reduction with potassium iodide) and arsenic(III) + DMA (acetic acid 0.12 mol/L). Total arsenic could be measured in HCl 6 mol/L, after arsenic(V) and DMA pre-reduction with a potassium iodide and stannous chloride mixture. Interference effects produced by heavy metal ions were also evaluated.