Ionic liquids as mobile phase additives in high-performance liquid chromatography with electrochemical detection: application to the determination of heterocyclic aromatic amines in meat-based infant foods.
ABSTRACT The beneficial effects of several ionic liquids (ILs) as mobile phase additives in high-performance liquid chromatography with electrochemical detection for the determination of six heterocyclic aromatic amines (HAs) have been evaluated for first-time. The studied ionic liquids were 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF(4)), 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIm-BF(4)) and 1-methyl-3-octylimidazolium tetrafluoroborate (MOIm-BF(4)). Several chromatographic parameters have been evaluated in the presence or absence of ILs, or using ammonium acetate as the most common mobile phase additive, with three different C18 stationary phases. The effect of the acetonitrile content was also addressed. In general, best resolution, lower peak-widths (up to 72.1% lower) and lower retention factors are obtained when using ILs rather than ammonium acetate as mobile phase additives. The main improvement was obtained in the baseline noise, being 360% less noisy for BMIm-BF(4), 310% for HMIm-BF(4), and 227% for MOIm-BF(4), when compared to ammonium acetate at +1000 mV. Different chromatographic methods using the best conditions for each IL were also evaluated and compared. Finally, the best chromatographic conditions using 1mM of BMIm-BF(4) as mobile phase additive, the Nova-Pak C18 column, 19% (v/v) of acetonitrile content in the mobile phase, and +1000 mV in the ECD, have been applied for the chromatographic analysis of six HAs contained in meat-based infant foods. The whole extraction method of meat-based infant foods using focused microwave-assisted extraction and solid-phase extraction has also been optimized. Extraction efficiencies up to 89% and detection limits ranged between 9.30 and 0.165 ng g(-1) have been obtained under optimized conditions.
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ABSTRACT: Self-assembled monolayers of thiolated β-cyclodextrins on a gold electrode have been developed for the determination of thiodianiline. Pentanethiol was employed to fill the empty space between the β-cyclodextrins on the surface. The formation of a 1:2 inclusion complex between thiodianiline and β-cyclodextrin was studied by electrochemistry. The parameters affecting the modification of the electrode and the determination of thiodianiline by square wave voltammetry were optimized. The limits of detection and determination are 190 and 205μg L−1, respectively. The accuracy, in terms of relative error values, is <7%. The precision, in terms of RSD (for n = 5), is <5%. The method was applied to the determination of thiodianiline in real wastewater samples with RSD values of <11% and an average recovery of 98% for all the spiking levels assayed. KeywordsGold electrode-Self-assembled monolayers-Thiolated cyclodextrins-Thiodianiline-Supramolecular chemistryMicrochimica Acta 04/2012; 171(1):41-47. · 3.43 Impact Factor
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ABSTRACT: While existing research has mainly focused on project management’s static view, our work investigates the impacts of projects’ structure and behavioural dynamics on their performance, with a specific focus on the influence of some peculiar development processes. A dynamic simulation model of a single-phase project was built using the system dynamics methodology. The model integrates several previously developed and tested project structures and adds a separate structure for the negotiation process. Simulations describe the behaviours generated by the interaction of customized development processes in single-phase projects. Project performances are measured in terms of time, quality and cost. Our research aims to show that development processes, as well as shared resource levelling techniques, significantly impact the dynamic behaviour of projects through the feedback, delays and nonlinear relationships which are usually omitted in traditional project management practice, as well as in methods, tools and models, but are very important descriptors of project complexity. Expanding the models used to manage projects to include dynamic features requires a change of focus by researchers and practitioners. The system dynamics methodology provides some of the tools for developing and implementing such an expansion in project models.Food Chemistry - FOOD CHEM. 05/2011;
- 09/2011; , ISBN: 978-953-307-605-8