Potentiometric detection in UPLC as an easy alternative to determine cocaine in biological samples

The analytical methods which are often used for the determination of cocaine in complex biological matrices are a prescreening immunoassay and confirmation by chromatography combined with mass spectrometry. We suggest an ultra‐high‐pressure liquid chromatography combined with a potentiometric detector, as a fast and practical method to detect and quantify cocaine in biological samples. An adsorption/desorption model was used to investigate the usefulness of the potentiometric detector to determine cocaine in complex matrices. Detection limits of 6.3 ng mL^?1 were obtained in plasma and urine, which is below the maximum residue limit (MRL) of 25 ng mL^?1. A set of seven plasma samples and 10 urine samples were classified identically by both methods as exceeding the MRL or being inferior to it. The results obtained with the UPLC/potentiometric detection method were compared with the results obtained with the UPLC/MS method for samples spiked with varying cocaine concentrations. The intraclass correlation coefficient was 0.997 for serum (n =7) and 0.977 for urine (n =8). As liquid chromatography is an established technique, and as potentiometry is very simple and cost‐effective in terms of equipment, we believe that this method is potentially easy, inexpensive, fast and reliable. Copyright © 2014 John Wiley & Sons, Ltd.     

The first coordination compounds of OP[NC4H8O]3 phosphoric triamide ligand: structural study and Hirshfeld surface analysis of SnIV and MnII complexes

The first X-ray crystal structures of coordination compounds of OP[NC₄H₈O]₃ phosphoric triamide (L) are investigated in Cl₂(CH₃)₂Sn(trans-L)₂ (1) and [Mn(H₂O)₄(trans-L)₂]Cl₂·2H₂O (2) as models of molecular and salt complexes for Hirshfeld surface (HS)-based analysis. The crystal packing of 1 includes weak interactions, while in the salt complex 2, a 2-D aggregate, along the (001) plane, is mediated by normal O–H?Cl and O–H?O hydrogen bonds. In the Hirshfeld study, the crystal cohesions of 1 and 2 are recognized via H?H, O?H/H?O, and Cl?H/H?Cl contacts. Among these interactions, hydrogen bonds O–H?Cl occur in the salt structure of 2, as well as some weaker hydrogen interactions as C–H?O (1 and 2), C–H?Cl (1), and O–H?O (2). The full fingerprint plots have nearly symmetric shapes for two independent molecules of 1, while an asymmetric shape appears for the cationic component of 2. To extract more detailed information on close intermolecular contacts, the molecular surface of the previously reported structure L was also mapped. The structure 2 is the first monomeric octahedral Mn(II)–phosphoric triamide complex reported so far. Furthermore, the HS analysis of 2 is the first such study on a cation–anion complex structure including phosphoric triamide ligand.     

A proper generalized decomposition approach for optical flow estimation

This paper introduces the use of the proper generalized decomposition (PGD) method for the optical flow (OF) problem in a classical framework of Sobolev spaces, ie, optical flow methods including a robust energy for the data fidelity term together with a quadratic penalizer for the regularization term. A mathematical study of PGD methods is first presented for general regularization problems in the framework of (Hilbert) Sobolev spaces, and their convergence is then illustrated on OF computation. The convergence study is divided in two parts: (a) the weak convergence based on the Brézis-Lieb decomposition and (b) the strong convergence based on a growth result on the sequence of descent directions. A practical PGD-based OF implementation is then proposed and evaluated on freely available OF data sets. The proposed PGD-based OF approach outperforms the corresponding non-PGD implementation in terms of both accuracy and computation time for images containing a weak level of information, namely, low image resolution and/or low signal-to-noise ratio (SNR).     

Design of multilayer high-dispersion mirrors using multi-swarm optimization method

Design of high-dispersion mirrors (HDMs) using a proposed multi-swarm optimization method is reported. We design HDMs for Yb:YAG disk oscillator at 1030 nm and ultrashort pulse Cr:YAG laser at 1550 nm. The results show that the optimum group delay dispersion and reflectance can be obtained with optimal number of layers. The proposed optimization method has a fast convergence rate and powerful global search ability and can be utilized effectively for the design of a variety of optical thin film filters.