Microfluidic paper-based analytical devices with instrument-free detection and miniaturized portable detectors

Microfluidic paper-based analytical devices (µPADs) have attracted much attention over the past decade because they offer clinicians the ability to deliver point-of-care testing and onsite analysis. Many of the advantages of µPADs, however, are limited to work in a laboratory setting due to the difficulties of processing data when using electronic devices in the field. This review focuses on the use of µPADs that have the potential to work without batteries or with only small and portable devices such as smartphones, timers, or miniaturized detectors. The µPADs that can be operated without batteries are, in general, those that allow the visual judgment of analyte concentrations via readouts that are measured in time, distance, count, or text. Conversely, a smartphone works as a camera to permit the capture and processing of an image that digitizes the color intensity produced by the reaction of an analyte with a colorimetric reagent. Miniaturized detectors for electrochemical, fluorometric, chemiluminescence, and electrochemiluminescence methods are also discussed, although some of them require the use of a laptop computer for operation and data processing.     

Retention mechanism of peptides on a stationary phase embedded with a quaternary ammonium group: A liquid chromatography study

We investigated the mechanisms involved in the retention of various peptides on a stationary phase embedded with a quaternary ammonium group (BS C23), by high-performance liquid chromatography. This was compared with peptide retention on a conventional reversed-phase C18 (RP C18) column under isocratic conditions, to understand better the various mechanisms involved. Chromatographic characterization of the two stationary phases with “model” compounds showed that BS C23 is less hydrophobic than RP C18 and induces electrostatic interaction (attraction or repulsion) with ionized compounds. If reversed-phase partitioning was the predominant retention phenomenon, for both stationary phases, the retention mechanisms in BS C23 provided different selectivity to that of RP C18. Electrostatic attraction or repulsion was clearly observed between peptides and the permanent positively charged group embedded in BS C23 depending on the pH. For most of the peptides, a weak anion-exchange mechanism was observed on the quaternary ammonium-embedded stationary phase if mobile phases at neutral pH and low ionic strengths were employed.     

Novel amino- and thio(substituted)-1,4-naphthoquinone (NQ) compounds: Synthesis and characterization

Abstract

Synthesis of new 1,4-naphthoquinone derivatives is important in terms of searching new biologically active substances. In particular, compounds with piperazine and thiol moiety in their structure, show a wide range of pharmacological activity such as anti-inflammatory, anticancer, anti-fungal, anti-bacterial, anti-allergic, apoptosis and radical scavenging activities. In this study, new amino- and thio(substituted) naphthoquinone derivatives were synthesized by the reaction of thiols and thioalcohols with four naphthoquinone compounds which were used as starting materials. The new compounds were purified by column chromatography. The structure of the compounds was confirmed by different spectroscopic techniques.     

A new CZE method for profiling human serum albumin and its related forms to assess the quality of biopharmaceuticals

We present a new CZE method, which uses a polyethylene oxide-coated capillary to separate native HSA from more than five of its structural variants. These variants include oxidized, truncated, and cysteinylated forms of HSA which can all be found in biopharmaceutical products. Both CE and MS confirmed the high degree of heterogeneity of HSA preparations. Recovery studies demonstrated that adsorption of HSA on the capillary was significantly reduced under the conditions we developed, which led to a satisfactory repeatability (RSD for migration times and relative peak areas were less than 0.2 and 7.0%, respectively). Assignment of the main peaks was attempted using in vitro degraded/stressed HSA. We used our method to test batch-to-batch comparability and detected slight quantitative differences in the proportion of native HSA in batches produced from different fractionation methods.     

Structural Study of Polymorphism in [La(Gly)3·2H2O](ClO4)3

Journal of Chemical Crystallography - The crystal structures of [La(Gly)3·2H2O](ClO4)3 were determined by X-ray diffraction analysis at temperatures 100 K and 300 K: space...     

Isolation of Chromium(VI) from Aqueous Solution by Electromembrane Extraction

Electromembrane extraction (EME) is a powerful extraction and preconcentration technique for ionizable species. However, the ionic contents in the sample can influence the extraction efficiency and system stability due to electrolysis. In this work, the electromembrane extraction of chromium(VI) was developed using various levels of ionic samples. 2-Nitrophenyl octyl ether was the most suitable supported liquid membrane that delayed the electrolytic occurrence of air bubbles at the electrodes due to its high viscosity and high dielectric constant properties. The electromembrane extraction method was optimized using 5?mM NaCl (630?µS?cm^?1); the applied potential was 100?V and the extraction time was 15?min. The enrichment factor of 80 was obtained over a linear working range of 10.0–80.0?µg?L^?1. The method performance was tested using mineral water, drinking water, tap water, and surface water. The method recoveries based on matrix-matched calibration were 95–125% with standard deviations within 15%.