Acid/extraction treatment of bivalves for organotin speciation

A method is described for leaching of nanogram amounts of monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPT), diphenyltin (DPT), triphenyltin (TPT), and monomethyltin (MMT) from bivalves. The procedure is based on soaking the samples in a water-hydrogen bromide mixture (1:1) with magnetic stirring for 30 min followed by extraction with a 0.04% (w/v) tropolone solution in dichloromethane for 2 h. Organotins are determined by GC-FPD after clean-up through a Florisil column and fat hydrolysis by 1mol/L NaOH, followed by derivatization through Grignard pentylation. The method has been applied for an investigation of the occurrence of organotins in bivalves in south-west Spain. Received: 3 September 1994 / Revised: 2 October 1996 / Accepted: 7 November 1996     

Thermal decomposition of ammonium monochloroacetate and ammonium monochloroacetate silicomolybdate

Journal of Thermal Analysis and Calorimetry - Les anomalies que nous avons observées, dans le cas de l'oxydation de fils de nickel, peuvent s'interpréter en faisant appel à...     

Dielectric-differential thermal analysis

A quantitative relation is given for the temperature function of the output voltage is thermodielectric analysis. Results obtained with zeolites show the validity of the equation.     

Dielectric-differential thermal analysis IV the role of water

A deeper understanding of the role of water in dielectric-differential thermal analysis is presented.We are grateful to Maria Elena Alfonso for sample preparation.     

Determination of dialkyldiselenides in water by gas chromatography-mass spectrometry using 1-fluoro-2,4-dinitrobenzene as derivatization reagent

The feasibility of gas chromatography-mass spectrometry for the speciation of traces of dialkyldiselenides in the presence of dialkylselenides and inorganic selenium species is described, and the procedure is applied to environmental samples. The analysis is based on the reaction of dialkyldiselenide species with 1-fluoro-2,4-dinitrobenzene after volatilization of selenium species as alkylselenols using a volatilization and trap device. Parameters affecting the volatilization and derivatization of the selenium compounds are discussed, and the performance of the method is described. The approach reaches detection limits in the order of nanograms (after a preconcentration step) and has been applied to the analysis of dimethyldiselenium and diethyldiselenium in natural waters.     

Intercalation compounds between nicotine and a high surface area Saponite

The retention of nicotine by a high surface area saponite has been studied using two methods: (1) in repose at room temperature, and (2) heating at 70 °C under reflux. Different contact times were considered for each method. The intercalation compounds obtained were studied by chemical analysis, X-ray diffraction, infrared spectroscopy and thermal analysis. Nicotine is retained both in the interlayer region and at the edge of clay particles. The amount of nicotine retained in the interlayer region has been calculated from thermal analysis and CHN measurements.     

Dielectric differential thermal analysis

The present paper deals with the role of guest molecules in the moleculer sieves systems.     

Uniform nanosized goethite particles obtained by aerial oxidation in the FeSO4-Na2CO3 system

Pure goethite particles in the nanometer size range (from approximately 200 to approximately 80 nm) with an elongated shape (axial ratio from approximately 5 to approximately 8) useful as iron precursors for magnetic recording have been prepared by oxidation of the suspensions resulting from the addition of sodium carbonate to Fe(II) sulfate aqueous solutions under a restrictive set of experimental conditions (Fe(II) concentration, carbonate/Fe(II) mole ratio, temperature, and air flow rate). In all cases, the goethite particles were formed by a dissolution-recrystallization mechanism through an intermediate green-rust phase. The particle size was determined by the carbonate/Fe(II) ratio (which controls the formation pH), the FeSO(4) concentration, and the air flow rate. The smallest particles (length 80 nm) were obtained for a high carbonate/Fe(II) mole ratio (>/=3), a low Fe(II) concentration (0.075 mol dm(-3)), and an air flow rate of 2 dm(3) min(-1). The goethite particles were also characterized by the electron diffraction and high-resolution TEM finding that they were monocrystalline, having the crystalline c axis parallel to the longest particle dimension.     

Comparison of three derivatization reagents for the analysis of Se(IV) based on piazselenol formation and gas chromatography-mass spectrometry

A comparison between the performance of three derivatizing reagents (4-chloro-o-phenylendiamine, 4-nitro-o-phenylendiamine and 2,3-diaminonaphthalene) for the analysis of selenite in environmental samples using gas chromatography-mass spectrometry (GC-MS) has been evaluated. The effects of different parameters (pH, temperature and time of derivatization, type and volume of organic solvent and time and number of extractions) on the derivatization reaction and extraction of the derivatives have been evaluated. Derivatization using 2,3-diaminonaphthalene took a longer time compared to those obtained using the other reagents. The highest sensitivity was obtained using 4-chloro-o-phenylendiamine. No matrix interferences were observed in tap, river and seawater using the three reagents.