Maria Luíza B. Tristão

Anhydrous copper(II) hexanoate from cuprous and cupric oxides. The crystal and molecular structure of Cu2(O2CC5H11)4

Abstract The synthesis and spectroscopic, magnetic and structural characterization of a complex of copper(II) with hexanoic acid, Cu2(O2CC5H11)4 are described. The same complex is formed by synthesis using either CuO or Cu2O. The compound exhibits a typical dinuclear paddle-wheel type structure, consisting of two copper(II) ions in square-pyramidal geometry bridged by four carboxylate anions in the xy plane. The IR spectrum shows that the ΔνCOO for this complex appears at 171 cm−1 which corresponds to a bridging bidentade mode of coordination of carboxylate-to-metal. Elemental analysis, EPR spectra and TG analysis were also performed. The magnetic susceptibility measurement confirms the antiferromagnetic nature of the copper–carboxylate coupling which is in agreement with the X-ray crystallography results.

Determination of low‐molecular‐weight amines and ammonium in saline waters by ion chromatography after their extraction by steam distillation

A new method was developed for the determination of ammonium ion, monomethylamine and monoethylamine in saline waters by ion chromatography. Steam distillation was used to eliminate matrix interferences. Variables such as distillation time, concentration of sodium hydroxide solution and analyte mass were optimized by using a full two-level factorial (2(3) ) design. The influence of steam distillation on the analytical curves prepared in different matrices was also investigated. Limits of detection of 0.03, 0.05 and 0.05 mg/L were obtained for ammoniumion, monomethylamine and monoethylamine, respectively. Saline water samples from the Brazilian oil industry, containing sodium and potassium concentrations between 2.0-5.2% w/v and 96-928 mg/L, respectively, were analyzed. Satisfactory recoveries (90-105%) of the analytes were obtained for all spiked samples, and the precision was ≤ 7% (n = 3). The proposed method is adequate for analyzing saline waters containing sodium to ammoniumion, monomethylamine and monoethylamine concentration ratios up to 28 000:1 and potassium to ammonium, monomethylamine and monoethylamine concentration ratios up to 12 000:1.

A new on-line version of the gold amalgamation trap for interference-free determination of Hg0 in crude oil and related products by Zeeman CV-AAS

A new on-line version of the gold amalgamation trap was proposed for the determination of Hg0 in crude oil and related products prior to its detection by atomic absorption spectrometry. On-line analyses were carried out by a homemade gold amalgamation trap (GAT), heated at 120 °C during the Hg0 amalgamation, coupled to a commercial mercury analyzer, containing a spectral corrector based on the Zeeman effect. The heating avoided the collection of many volatile hydrocarbons onto the trap, and the Zeeman-effect corrector avoided the interferences caused by part of the organic vapors, which were collected onto the trap during the Hg0 amalgamation. Experimental parameters such as carrier gas flow, Hg0 release temperature and Hg0 amalgamation time were investigated. LOD and LOQ values of 0.06 and 0.21 μg L−1 Hg0 were obtained, respectively. Precision was always better than 10%. Quantitative Hg0 recoveries (85–116%) were obtained for the spiked certified reference materials and spiked crude oil, diesel and gas condensate samples.