Electrochemical determination of zearalenone using a label-free competitive aptasensor

An in situ preparation of metal-organic framework (HKUST-1) on the surface of an organic polymer is reported. The hybrid material was evaluated as sorbent for solid-phase extraction (SPE) of oxygenated and nitrated polycyclic aromatic hydrocarbons (PAHs). The growth of HKUST-1 on MAA-based polymer was accomplished using a layer-by-layer assembly strategy. The HKUST-1-polymer was characterized using powder X-ray diffraction and scanning electron microscopy to demonstrate the incorporation of MOF crystals onto the polymer surface. The MOF (nano)crystals were characterized using high-resolution transmission electron microscopy and high-angle annular-dark-field scanning transmission electron microscopy. The water-stable MOF-polymer was evaluated as SPE sorbent, and several variables that can influence the extraction recoveries of PAH derivatives were investigated. Under the selected conditions, the detection limits varied between 4 and 21 ng·L−1, and the precision (relative standard deviation) was below 12%. The recovery values for spiked solutions ranged from 95 to 104%, and the enrichment factor achieved was close to 1000-fold using a high sample volume (100 mL) and very low desorption volume (100 μL). The SPE enrichment combined with HPLC and DAD detector was successfully applied to the extraction and determination of polycyclic hydrocarbons in environmental water samples.     

Synthesis of new liquid crystalline diglycidyl ethers

The phenolic Schiff bases I-VI were synthesized by condensation reactions between various diamines, namely o-dianisidine, o-tolidine and ethylenediamine with vanillin or p-hydroxybenzaldehyde and subsequent reactions between these phenolic Schiff bases and epichlorohydrin to produce new diglycidyl ethers Ia-VIa. The structures of these compounds were confirmed by CHN, FT-IR, (1)H-NMR, and (13)C-NMR spectroscopy. Their thermotropic liquid crystalline behavior was studied using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). All the diglycidyl ethers prepared exhibit nematic mesophases, except for Va and VIa, which did not show any transition mesophases, but simply flow to liquids.     

Spectrophotometer with enhanced sensitivity for uric acid detection

A spectrophotometer with an LED as the light source for uric acid detection is proposed in this work. The mechanism of uric acid detection is based on energy absorbed by sodium urate, which is a chemical product of uric acid and sodium hydroxide solution. For the performance validation, comparison between the spectrophotometer with an LED and halogen lamp is carried out. Measurement results suggest that the spectrophotometer system with LED light has better sensitivity than that with halogen light. At a 460 nm wavelength,the sensitivity for the spectrophotometer with an LED is 0.0046 dL/mg, which is 73% higher than that with halogen light that records 0.0012 dL/mg. This enhanced sensitivity is attributed to the higher luminous efficacy of the LED light beam. As a result, a larger amount of flux interacts with the sample, leading to the sensitivity enhancement. The spectrophotometer with an LED is also applied for the detection of uric acid in a real human urine sample. Based on the experimental data at a 460 nm wavelength, the method manages to achieve the sensitivity of 0.0016 dL/mg, accuracy of 96.01%, limit of detection of 4.79 mg/dL, and limit of quantification of 14.52 mg/dL. These findings show that the use of LED as the input light source is promising for the spectrophotometer.     

A Comparative Study of Gas Flooding and Foam-Assisted Chemical Flooding in Bentheimer Sandstones

Transport in Porous Media - A laboratory study of principal immiscible gas flooding schemes is reported. Very well-controlled experiments on continuous gas injection, water-alternating-gas (WAG)...     

Development of surface treated nanosilica for wettability alteration and interfacial tension reduction

The present study examines and compares the effect of surface treatments of nano-silica using internal olefins sulphonates (IOS_20–24 and IOS_19–23), anionic surfactants. The effect of surface modification on colloidal stability, wettability alteration and oil-water interfacial tension reduction were analyzed. Silica nanoparticles were characterized using Field Emission Scanning Electron Microscope (FESEM) and integrated energy-dispersive X-ray spectroscopy (EDX) before and after surface treatment. Using Turbiscan classic, the optimal nanosilica concentration and inspection of the coated particles dispersion stability with the help of light transmission behavior through the nanofluid was carried out. The stability was found to be enhanced as the mean light transmission declined only after surfactant treatment in both IOS coated nano-silicas but IOS_19–23 O-342 coated dispersions proved to be more stable among all three. RAME-HART Goniometer was used to perform interfacial tension (IFT) and contact angle measurements. IFT was found to be reduced by 48% after the surfactant treatment in case of IOS_19–23 O-342 coated nanosilica. Both surface treatments of nanosilica and increasing silica concentration caused significant reduction and altering wettability towards more water wet. The results revealed that IOS coatings improved the efficiency of NPs dispersion in terms of altered wettability and reduced IFT that mimics their potential for EOR applications.