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The purpose of this work is to achieve the improvement of mechanical properties of polyamide 12 through dispersion of graphene-like nanofillers, for its use in Powder Bed Fusion. Nanocomposites have been prepared by conventional injection moulding in order to determine the mechanical and electrical behaviour of the different systems as a previous step for the design of new materials for Powder Bed Fusion. Structural characterisation and mechanical and electrical properties assessments were performed, showing the improvement of stiffness and mechanical strength for the prepared nanocomposites, compared to pristine polyamide. Electrical conductivity has been introduced as well in some of them. This enhancement of properties, together with the first tests carried out on nanocomposites prepared with Powder Bed Fusion, makes this study a starting point to obtain commercially interesting materials for this additive manufacturing technique.

This work reports on the design and development of nanocomposites based on a polymeric matrix containing biodegradable Polylactic Acid (PLA) and Polyhydroxyalkanoate (PHA) coated with either Graphite NanoPlatelets (GNP) or silver nanoparticles (AgNP). Nanocomposites were obtained by mechanical mixing under mild conditions and low load contents (&lt, 0.10 wt %). This favours physical adhesion of the additives onto the polymer surface, while the polymeric bulk matrix remains unaffected. Nanocomposite characterisation was performed via optical and focused ion beam microscopy, proving these nanocomposites are selectively modified only on the surface, leaving bulk polymer unaffected. Processability of these materials was proven by the fabrication of samples via injection moulding and mechanical characterisation. Nanocomposites showed enhanced Young modulus and yield strength, as well as better thermal properties when compared with the unmodified polymer. In the case of AgNP coated nanocomposites, the surface was found to be optically active, as observed in the increase of the resolution of Raman spectra, acquired at least 10 times, proving these nanocomposites are promising candidates as surface enhanced Raman spectroscopy (SERS) substrates.

Chitosan/bacterial cellulose composite films containing diamond nanoparticles (NDs) with potential application as wound dressing are introduced. Microstructural studies show that NDs are uniformly dispersed in the matrix, although slight agglomeration at concentrations above 2 wt % is seen. Fourier transform infrared spectroscopy reveals formation of hydrogen bonds between NDs and the polymer matrix. X-ray diffraction analysis indicates reduced crystallinity of the polymer matrix in the presence of NDs. Approximately 3.5-fold increase in the elastic modulus of the composite film is obtained by the addition of 2 wt % NDs. The results of colorimetric analysis show that the composite films are transparent but turn to gray-like and semitransparent at high ND concentrations. Additionally, a decrease in highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gap is also seen, which results in a red shift and higher absorption intensity towards the visible region. Mitochondrial activity assay using L929 fibroblast cells shows that the nanocomposite films are biocompatible (&gt, 90%) after 24 h incubation. Multiple lamellapodia and cell-cell interaction are shown. The results suggest that the developed films can potentially be used as a flexible platform for wound dressing.

To attend the growing consumer demand for novel ready-to-eat fresh cut fruits packaging polylactic acid (PLA)-based active packaging was realized. The aim of these packaging is to provide an improved protection and even to extend their shelf-life. PLA-based active packaging was prepared by adding nanoclays and surfactants in its formulation. The evaluation of PLA-nanocomposite packaging was done in comparison to pristine PLA and conventional plastic (polyethylene terephthalate, PET) using fresh-cut melons. Physicochemical properties were investigated by the means of weight loss, visual appearance, pH, colour, and firmness. In addition, microbial profile was tested via microbiological assays. In order to evaluate the environmental impact of PLA-based active packaging compared to commonly used PET, life cycle assessment (LCA) was conducted. In terms of physicochemical and antimicrobial properties, the results clearly showed that the presence of nanoclays and surfactants in the PLA formulations improved their performance, thus contributing to bring the characteristic and behaviour of PLA packages close to those of PET. Furthermore, assessment of life cycle environmental impacts indicated that PLA packaging with nanoclays had the highest environmental performance.

Magnetic nanoparticles (MNPs) were deposited onto multiwalled carbon nanotubes (MWCNTs) by in situ high-temperature decomposition of the magnetic precursor [iron(III)] and MWCNTs, in ethylene glycol. This one-step synthetic method was applied to commercially available carbon nanotubes (CNTs). Scanning electron micrographs of the resulting products revealed that MNPs decorated the surface of the MWCNTs. The hybrid nanoparticles thus obtained were used for sampling and cleanup in the determination of eight fluoroquinolones (FQs) and two quinolones (Qs) at trace levels by ultra performance liquid chromatography (UPLC). A systematic study of analyte adsorption and desorption was conducted with MNPs and MWCNTs separately. Although both solid phases adsorbed the analytes to some extent, the much higher recoveries were obtained by using the MNP-MWCNT composite which was thus selected to treat plasma samples containing FQs and Qs. Lower accuracies were determined at spiked plasma compared to the standard solution caused by the complexation affinity of the analytes with proteins because high recoveries were observed when deproteinization was performed before treating the sample with the magnetic MWCNTs. The performance characteristics of the optimized method were determined, and the method was applied to the analysis of plasma samples from antibiotic-treated patients. On the basis of the results, the use of an in situ synthesized MWCNT-MNP composite allows the simple, expeditious sampling and treatment of such complex biological samples for the subsequent determination of FQs and Qs present at free form.

Sample treatment is one of the most important stages in the analytical process. In the past few years, there have been many advances in preconcentration techniques and extraction of analytes from complex samples. Well-known sample treatments based on extractions (e.g., solid-phase extraction, liquid-liquid extraction, solid-phase microextraction and pressurized liquid extraction) or membranes (e.g., electromicrodialysis) can be improved by using electric fields. This has led to a new trend in analytical chemistry. We present a comprehensive, illustrated review of sample treatments using electric fields.

Sample preparation procedures are in most cases sample- and time-consuming and commonly require the use of a large amount of solvents. Automation in this regard can optimize the minimal-needed injection volume and the solvent consumption will be efficiently reduced. A new fully automated sample desalting and pre-concentration technique employing microextraction by packed sorbents (MEPS) cartridges is implemented and coupled to an ion cyclotron resonance Fourier-transform mass spectrometer (ICR-FT/MS). The performance of non-target mass spectrometric analysis is compared for the automated versus off-line sample preparation for several samples of aqueous natural organic matter. This approach can be generalized for any metabolite profiling or metabolome analysis of biological materials but was optimized herein using a well characterized but highly complex organic mixture: a surface water and its well-characterized natural organic matter and a marine sample having a highly salt charge and enabling to validate the presented automatic system for salty samples. The analysis of Suwannee River water showed selective C18-MEPS enrichment of chemical signatures with average H/C and O/C elemental ratios and loss of both highly polar and highly aromatic structures from the original sample. Automated on-line application to marine samples showed desalting and different chemical signatures from surface to bottom water. Relative comparison of structural footprints with the C18-concentration/desalting procedure however enabled to demonstrate that the surface water film was more concentrated in surface-active components of natural (fatty acids) and anthropogenic origin (sulfur-containing surfactants). Overall, the relative standard deviation distribution in terms of peak intensity was improved by automating the proposed on-line method. © 2009 Springer-Verlag., G. Morales-Cid wishes to thank the Spain’s Ministry of Innovation and Science for the award of a FPI fellowship (Grant BES-2005-10603) to work with the German colleagues and the additional economic support within the mobility program

This paper reports for the first time the use of microextraction by packed sorbent in combination with CE. The combined system was used to determine anesthetic drugs in human plasma. A microdialysis fiber was coupled on-line to the microextraction unit in order to distinguish between free and total concentrations of drugs. The system was automated by connecting the microextraction unit to a syringe pump and interfacing it to a computer. The ensuing method allows the determination of 10 microg/L concentrations of free drugs and 1 microg/L concentrations of total drugs from only 200 microL of sample with an RSD of less than 9%.

This paper describes a new and innovative way to integrate microextraction by packed sorbents (MEPS) into commercial CE equipment. The suggested integration allows the automatic sample cleanup and preconcentration requiring only a few microliters of sample and no additional hardware and software. The MEPS was integrated in the outlet region of a commercial CE equipment cartridge in order to provide easy manipulation and exchange. The robustness of the proposed integration was demonstrated by the design and use of a (MEPS)-nonaqueous capillary electrophoresis (NACE)-MS method used to determine fluoroquinolones "FQs" (namely, ofloxacin, marbofloxacin, enrofloxacin, danofloxacin, and difloxacin) in urine. The method allows the analysis of micrograms per liter of FQs to be carried out with only 48 microL of urine sample. The obtained LODs were in the range 6.3-10.6 microg/L. An analysis of spiked urine samples was used to validate the method. Absolute recoveries were in the range of 71-109% while the precision expressed as repetitivity of peak area was lower than 5.9%.

Two electrokinetic methods for the separation of phthalates are proposed. One uses 25 mM sodium borate and 50 mM sodium taurodeoxycholate adjusted to pH 2.8, and the other uses 15 mM ammonium tetraborate, 100 mM SDS, 0.25% w:v hydroxypropylmethyl cellulose (HPMC) and 5% v:v methanol (MeoH) adjusted to pH 9. The BGE containing SDS micelles as the pseudo-stationary phase provided better analytical figures of merit, particularly as regards LOD (0.4-1.4 mg/L) and precision (1.1-6.5%). Adding MeoH and HPMC to the BGE proved essential in order to obtain narrow and symmetric peaks. The proposed method was successfully used to determine phthalates in virgin olive oil. Recoveries from spiked samples ranged from 96 to 106%. The precision obtained in the analysis of real samples, as RSD, was better than 6.8%.

A substantial demand currently exists for analytical methods affording the determination of very low concentrations of analytes in complex matrices, such as those of environmental and biological samples, as simply as possible. However, the pretreatment of complex samples, which is unavoidable prior to CE-MS analysis, is usually complicated and time-consuming. In this work, we used voltage-assisted SPE for the first time as an alternative to conventional treatments for preconcentrating and purifying analytes. To this end, we used a simple flow system coupled on-line to CE-MS equipment. The system is quite robust and provides reproducible peak areas (the precision ranges from 2.5 to 3.8%). Also, it provides increased sensitivity affording the determination of trace amounts (nanogram per liter levels) of analytes in only a few milliliters of sample. The proposed system was applied to the determination of members of two compound families (viz. tetracyclines and amines).

An immunoaffinity purification method coupled on-line to capillary electrophoresis (IACE) which allows the determination of several isoforms of intact alpha-1 acid glycoprotein (AGP) in serum samples using UV detection is developed. The immunoaffinity step is based on anti-AGP antibodies (Abs) covalently bound to magnetic beads (MBs) which are captured at the inlet end of the capillary using permanent magnets placed inside the cartridge of the CE instrument. The on-line method includes injection of the MBs with the Ab bound (MBs-Ab) and their trapping by the magnets at the entrance of the separation column, injection of serum sample and capture of AGP by the Abs, release of captured AGP, focus of desorbed protein, separation of AGP isoforms, and removal of MBs-Ab. The optimization of the different factors involved in each step allowed purification, separation and detection of AGP isoforms in a single electrophoretic analysis in about 1. h. Automation, sample and reagents consumption as well as analysis time was improved compared to off-line alternatives which use purification of AGP in an immunochromatographic column and CE separation of AGP isoforms in two independent operations. The analytical methodology developed allows the separation of 10 AGP isoforms in serum samples from a healthy donor. For a serum sample, precision (expressed as relative standard deviation) in terms of corrected area percentage was better than 0.5% for each peak accounting for more than 10% of total AGP and it was better than 4.0% in terms of relative migration time of each AGP isoform considering the whole process. © 2013 Elsevier B.V.

On many occasions, sample treatment is a critical step in electrophoretic analysis. As an alternative to batch procedures, in this work, a new strategy is presented with a view to develop an on-capillary sample cleanup method. This strategy is based on the partial filling of the capillary with carboxylated single-walled carbon nanotube (c-SWNT). The nanoparticles retain interferences from the matrix allowing the determination and quantification of carbohydrates (viz glucose, maltose and fructose). The precision of the method for the analysis of real samples ranged from 5.3 to 6.4%. The proposed method was compared with a method based on a batch filtration of the juice sample through diatomaceous earth and further electrophoretic determination. This method was also validated in this work. The RSD for this other method ranged from 5.1 to 6%. The results obtained by both methods were statistically comparable demonstrating the accuracy of the proposed methods and their effectiveness. Electrophoretic separation of carbohydrates was achieved using 200 mM borate solution as a buffer at pH 9.5 and applying 15 kV. During separation, the capillary temperature was kept constant at 40 degrees C. For the on-capillary cleanup method, a solution containing 50 mg/L of c-SWNTs prepared in 300 mM borate solution at pH 9.5 was introduced for 60 s into the capillary just before sample introduction. For the electrophoretic analysis of samples cleaned in batch with diatomaceous earth, it is also recommended to introduce into the capillary, just before the sample, a 300 mM borate solution as it enhances the sensitivity and electrophoretic resolution.