Determination of styrene in olive oil by an automatic purge-and-trap system coupled to gas chromatography-mass spectrometry

Summary A new gas chromatographic method using an automatic purge-and-trap system coupled to a GC with mass selective detection to analyze styrene at the parts-per-trillions (ng kg^–1) level is described. The method shows a good sensitivity and the detection limit is 10 ng kg^–1 with a relative standard deviation (RSD) of 4.7% for 164 ng kg^–1 styrene in olive oil. This analytical method has been successfully applied to the analysis of styrene in extra-virgin olive oil from the European market.     

Mössbauer and infrared spectroscopic studies of novel mixed valence states in cobaltous ferrocyanides and ferricyanides

Novel mixed valence states have been obtained by the treatment of cobaltous ferrocyanides (Co⁺²Fe^II) and ferricyanides (Co⁺²Fe^III) in an ozone flow. The CN stretching bands occur at 2085 cm^–1 for Co⁺²Fe^II and at 2160 cm^–1 for Co⁺²Fe^III. After the ozonization process of Co⁺²Fe^II, an intense band approximately at 2125 cm^–1 is detected. This intermediate band must correspond to a mixed valence state of the type: Fe^II–CN–Co²⁺–NC–Fe^III Mössbauer spectra recorded in situ during the ozonization of Co⁺²Fe^II show the presence of two components: a doublet with isomer shift and quadrupole splitting values close to the cobalti ferricyanide and a very broad line for the mixed valence state. From the Mössbauer and infrared spectra of the aged samples of the Co⁺²Fe^II after ozonization, a relaxation process to the initial state of the samples is observed but the mixed valence state is stable.     

Analysis of drugs by AAS via formation of ion pairs

A new procedure for determining nitrogenated bases by forming ion pairs with Fe(SCN)6^3– is studied. The method consists of extracting the ion pair formed by a nitrogenated base and the inorganic complex Fe(SCN)6^3– into an organic phase, and measuring the iron in the organic phase by AAS at 248.3 nm. The optimal experimental conditions for determining amylocaine, avacan, bromhexine, diphenhydramine and papaverine are studied. The organic phase used is 1,2-dichloroethane. The standard deviation of the method varies between 10^–1 and 10^–2. The interferences produced by various substances are studied.     

Mineral speciation of copper and zinc in flying ash from a thermal power plant

Summary We studied the mineral speciation of Cu, Zn and Hg in fly ash from a large thermal plant burning lignite. By applying various treatments carried out under different conditions and taking into account the solubility and physical properties (boiling and melting point, etc.) and the behaviour towards combustion of the different possible compounds, we concluded that the ash assayed contained 109.6, 114.4 and 14.30 g/g of zinc silicate, zinc oxide and/or zinc sulphide and metal zinc, respectively, as well as 24.5 g/g of copper silicate and 31.2 g/g of a mixture of copper oxide, sulphide and metal. The formation of these compounds in the combustion of lignite is discussed.     

Determination of lead in wines by hydride generation atomic absorption spectrometry.

The optimization of lead hydride generation in aqueous ethanolic media and the influence on its generation of the wine components, both white and red, have been studied. These interferences were overcome by careful control of the parameters affecting hydride generation and the procedure was applied to the determination of Pb in wines. The method is fast, accurate and sensitive and can be used to quantify 24 ppb of Pb in wines.