Highlighted articles (November 27th, 2015)

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

1. Application of graphitic sorbent for on-line microextraction of drugs in human plasma samples. Graphitic carbon has a great potential as sorbent since it may develop different interaction chemistries with target compounds. Commercial graphitic carbons like graphitized carbon black or porous graphitic carbon presents some disadvantages including a lack of mechanical stability or a high retention (almost irreversible) of some analytes. These shortcomings are faced in this article where a new carbon material is presented. The new material is based on the deposition of a graphitic carbon layer over an inert substrate like alumina. This combination increases the mechanical strength which is key for chromatographic uses. The material has been packed in a lab made microextraction in packed sorbent (MEPS) device and it has been applied for the extraction of ropivacaine and lidocaine from plasma samples showing a better clean-up performance than conventional protein precipitation procedure. Link to the article

2. In-line coupling of single drop microextraction with capillary electrophoresis-mass spectrometry. This article describes for the first time the in-line combination of single drop microextraction (SDME) and CE using MS as instrumental technique. Even when a sophisticated and selective technique, such as MS, is used a previous sample treatment is required to remove matrix components (avoiding in this way ionization suppression) and preconcentrate the target analytes. The in-line coupling is not a simple process and requires several modifications of the system. First of all, the inlet tip of the capillary should be chemically modified, including hydrophobic moieties, to favor the stabilization of an octanol drop. This drop acts as chemical barrier between the sample and the acceptor phase (buffer of the CE) that present different pHs. This pH gradient is the responsible of the final extraction. The handling of the organic drop in the capillary tip is the most difficult process and a buffer reservoir in the outlet tip is required to avoid the introduction of air into the system. Link to the article

 

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