Highlighted articles (October 22, 2014)

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We recommend the following articles that deal with different aspects related to sample preparation.

1. Energy-dispersive X-ray spectrometry combined with directly suspended droplet microextraction for determination of dissolved silicate in surface water via silico molybdenum blue complex. Dr. Pytlakowska from the University of Silesia (Poland) faces up the determination of silicate in samples by energy-dispersive X-ray spectrometry, which is not especially sensitive for this determination due to the low energy of the Kα line of silicon. In order to overcome this limitation, a indirect method based on the use of molybdenum (a more intense emitter) as marker is proposed. For this purpose, silicate is transformed into silicomolybdenum blue which is finally isolated and preconcentrated by means of suspended droplet microextraction. After the extraction, the organic solvent is deposited over a polymeric membrane where molybdenum (whose concentration is related to the original silicate in the sample) is measured. The limit of detection (6 ng/mL) and the precision (RSD lower than 6.7%) clearly show the potential of the combination. Link to the article

2. Polyelectrolyte coatings prevent interferences from charged nanoparticles in SPME speciation analysis. The use of PDMS as sorptive phase may be problematic when the sample contains dispersed charged nanoparticles or proteins. These materials can modify the normal extraction of a given analyte. In this article, conventional PDMS coating is modified and covered with two polyelectrolyte layers in order to avoid this negative effect. This modification involves the previous oxidation of the PDMS fiber to produce negative charged functional groups on the surface and their subsequent covering with a cationic polyelectrolyte [poly(diallyldimethylammonium chloride)] and a negative one [poly(sodium 4-styrenesulfonate)]. In such conditions, negative charged nanoparticles are not able to diffuse towards the PDMS phase due to repulsive electrostatic interaction while the target analyte (triclosan) is extracted following non-polar interactions. Link to the article

3. Solid-phase microextraction/gas chromatography–mass spectrometry method optimization for characterization of surface adsorption forces of nanoparticles. The surface reactivity of nanoparticles (NPs), which is essential to understand their potential toxicity, can be calculated studying the interactions of model organic compounds with those NPs. This is the starting hypothesis, supported by previous research, of this interesting article. The authors develop and optimize an SPME-GC/MS methods that is capable to study the organic compounds-NPs interaction. The study is focused in two different NPs (SiO2 and Au) and tests up to 33 different compounds. The performance of the proposal is well described and the results are comparable with those published in the literature. If you are interested in the toxicity of NPs and the ways to calculate it, this article is for you.
The article is freely available on Internet (Open Access). Link to the article

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