SummaryA experimental design optimization method is demonstrated for evaluation of the resolution of the performance mixture used in the proposed ASTM test to determine the aromatic content of aviation fuels.The method uses a Doehlert experimental matrix test to optimize the resolution and analysis time by varying the pressure and temperature of the supercritical carbon dioxide mobile phase.The separation between saturated and aromatic compounds was optimized using only seven experiments. With this procedure, the analysis time required for determination of the total aromatic content of more complex samples can be reduced to less than 10 min.

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The atmospheric particulates from the Caracus Valley in Venezuela and the fluvial particulates transported by the Tuy River into the Caribbean sea have been evaluated for Pb, Cu and Zn with the purpose of determining the contamination levels in the study area. The atmospheric particulate samples were collected in the city of Caracas using a low volume sampler whereas the fluvial particulate were collected at the mouth of the Tuy River. The particulate samples were analysed by flame or graphite furnace atomic absorption spectrometry depending upon the concentration levels of the heavy metal under study. The results obtained for the fluvial particulates enabled estimates to be made of the total anthropogenic flux of Cu (383 ton year(-1)), Pb (528 ton year(-1)) and Zn (865 ton year(-1)). These results yield annual per capita inputs for Cu (96 g),Pb (132 g) and Zn (216 g) which greatly exceed those from global anthropogenic emissions. The weighted average concentration of Pb (1.13 %) found in the atmospheric particulates was much higher than those for Cu (140 mg kg(-1)) and Zn (200 mg kg(-1)) and reflects the high motor car traffic in the Caracas Valley. The anthropogenic/natural ratios estimated in this study were as follows: 2.6 for Pb; 1.5 for Cu and 1.5 for Zn. This indicates that anthropogenic inputs for Cu, Pb, and Zn in the study area exceed those from natural sources, cars being the major source for Pb and industrial activities the major sources for Cu and Zn.

The determination of lead in whole blood by electrothermal atomisation atomic absorption spectrometry using a Varian Model AA875 atomic absorption spectrometer coupled to a Varian Model GTA-95 graphite furnace is reported. An evaluation was undertaken to determine whether the use of (NH4)*HP04 was beneficial when using tube and platform atomisers. Optimisations of the furnace heating conditions and of the best absorbance mode and sensitivity in both systems were also undertaken. The analysis of a target standard showed that it was possible to determine lead in blood by simple dilution with Triton X-100 using platform atomisation and the peak-area calculation mode. Calibration was carried out by direct comparison with linear working graphs prepared from aqueous standards.

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