Research Advances in Ion Channel-based Electrochemical Sensing Techniques

During the past few years, the electrochemical sensing techniques based on ion channels have attracted considerable attention. Nowadays, these techniques have been widely used in DNA sequencing, measurement of molecular interactions, and detection of inorganic ions and biological species. Hence, in this review, the research progresses of the ion channel-based electrochemical techniques including amperometry, conductometry and potentiometry in chemical and biological sensing are addressed from the perspective of different electrochemical methods. The sensing mechanism and fabrication process of these sensing methods are mainly introduced. In addition, the further research orientations of the electrochemical sensing based on ion channels are prospected.     

Development of a low flow‐resistive charged nanoporous membrane in a microchip for fast electropreconcentration

A nanoporous poly‐(styrene sulfonate) (poly‐SS) membrane was developed for fast and selective ion transport in a microfluidic chip. The poly‐SS membrane can be photopolymerized in‐situ at arbitrary location of a microchannel, enabling integrated fluidics design in the microfluidic chip. The membrane is characterized by a low hydraulic resistance and a high surface charge to maximize the electroosmotic flow and charge selectivity. The membrane characteristics were investigated by charge‐selective electropreconcentration method. Experimental results show membranes with various percentages of poly‐SS are able to concentrate anions (fluorescein and TRITC‐labeled BSA). The anion‐selective electropreconcentration process is stable and 26‐times faster than previously reported poly‐AMPS (2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) based system. The electropreconcentration was also demonstrated to depend on the sample valency and buffer concentration.     

A novel,simple and robust method for the analysis of sulfonamides in fish farming water samples using column switching liquid chromatography

A novel method for the online extraction and preconcentration of four sulfonamides was developed using column switching liquid chromatography. Sulfadiazine, sulfathiazole, sulfamethoxypyridazine and sulfamethoxazole were analysed in water samples and preconcentrated in a C18 guard column. Suitable validation parameters were obtained, such as precision, accuracy and relative recovery, in accordance with the validation guidelines of the Food and Drug Administration. Low limits of detection (0.05–0.09 µg L^?1) and quantification (0.30 µg L^?1, for all of them) were obtained. The quadratic polynomial model was used to adjust the calibration data, and the coefficients of determination were higher than 0.999 for all the analytes. The method was shown to be robust to the assayed parameters according to Youden’s test. The proposed method was successfully used to determine sulfonamides in 11 different fish farming water samples, in which sulfadiazine (0.732 µg L^?1), sulfamethoxazole (0.531 µg L^?1), sulfathiazole (0.546–1.856 µg L^?1) and sulfamethoxypyridazine (0.369–1.509 µg L^?1) were found.     

3.66μm激光外差光谱仪设计与水汽柱浓度反演

激光外差光谱测量技术具有光谱分辨率高、探测灵敏度高、成本低等特点,近年来在温室气体探测、激光大气传输等领域得到了广泛的应用。以3.66 μm 分布反馈式带间级联激光器作为本振光源搭建了一套高分辨率激光外差太阳光谱测量装置,实现了水汽吸收光谱的实时测量,并利用最优估算法对整层大气中的水汽柱浓度进行了反演,得到合肥地区2019年5月22日和23日的水汽柱浓度。反演结果与同步进行观测的傅里叶变换光谱仪EM27/SUN测量结果变化趋势一致,相关性优于0.8,偏差小于15%。研究结果表明,搭建的激光外差测量装置能够实现大气中水汽吸收光谱的实时测量以及水汽柱浓度的精确反演,同时为后续的水汽浓度廓线测量与研究奠定了基础。     

Paramagnetic defects induced by ion implantation in oxide glasses

Radiation defects induced by ion bombardment of multicomponent oxide glasses of five compositions (phosphates and borosilicates) were investigated by means of electron paramagnetic resonance (EPR). The samples were implanted with N⁺, O⁺, Ar⁺, Mn⁺, Cu⁺ and Pb⁺ ions at energy E=150 keV at three different doses between 3×10¹⁵ and 10¹⁷ ions/cm². The broad anisotropic EPR spectra with principal g-values answering the relationship g_z>g_y>g_x˜g_e (g_e is g-factor of free electron) were observed for the samples of all five compositions. The g-values depend on glass composition. For example, g_z ranges from 2.016 to 2.057. Computer simulation shows that the spectra of many samples are superpositions of two spectra with g-values answering the mentioned relationship. These spectra are attributed to molecular O₂⁻ ions weakly coupled with glass network. In some samples narrow almost symmetric lines with g=2.0025±0.0005 were observed. The possible radiation defects responsible for this signal are discussed.     

Thermal stability of compressively strained Si/relaxed Si1-xCx heterostructures formed on Ar ion implanted Si (100) substrates

Thermal stability of compressively strained Si/relaxed Si_1-xC_x heterostructure formed with the defect control by Ar ion implantation was investigated. It was found that compressive strain is sustained up to 900 °C without prominent change in surface roughness. From the X-ray diffraction reciprocal space mapping, it was found that relaxed Si_1-xC_x layer is stable up to at least 800 °C, and compressively strained Si_1-xC_x with relatively large thickness is formed by annealing at temperatures higher than 900 °C owing to redistribution of C atoms. These results indicate that the compressively strained Si/relaxed Si_1-xC_x heterostructure formed by Ar ion implantation technique is available up to at least 800 °C and has a potential to be used at more than 900 °C.     

A Hybrid Approach to Maximize the Lifetime of Directional Sensor Networks with Smoothly Varying Sensing Ranges

The difficulty of maximizing the lifetime in directional sensor networks has gained increasing atten-tion recently. Most of the existing studies are focused on directional sensors with single or several predefined sensing ranges. In the present study, directional sensors can change sensing ranges smoothly. We address the problem of maxi-mizing the lifetime in directional sensor networks with such smoothly varying sensing ranges,and propose a hybrid ap-proach that combines a column generation method with an immune genetic algorithm. We search for attractive columns with the genetic algorithm, and optimize them by designing dynamic vaccines. Computational results demon-strate the performance of the proposed approach. Mean-while,the advantage of the mentioned sensors in terms of solution quality is also revealed.     

Packing density of slurry-packed capillaries at low aspect ratios

The average interparticle voidage or porosity (epsilon(inter)) in cylindrical capillaries is studied in dependence on the column diameter (d(c)) to particle diameter (d(p)) ratio for 5 < d(c)/d(p) < 50. Using optimized slurry and packing solvents, high pressure and ultrasonication, 5 mum-sized porous C18-silica particles were slurry-packed into fused-silica capillaries having ids from 30 to 250 mum. Packing densities are assessed by a polystyrene standard which is size-excluded from the intraparticle pore space of the packings. For d(c)/d(p) > 35 densely packed beds are realized (epsilon(inter) = 0.36-0.37), while for decreasing aspect ratios an exponential increase in epsilon(inter )is observed reaching epsilon(inter ) approximately 0.47 at d(c)/d(p) = 5. This behaviour is ascribed to a combination of the geometrical wall effect operating in the direct vicinity of the column wall, caused by the inability of the particles to form a dense packing against the hard surface of the column wall, and particle characteristics like the size distribution, shape and surface roughness. Results are compared with the literature data to address also the importance of absolute particle size in studying structure-transport relations in packed beds in dependence on the aspect ratio d(c)/d(p).     

Automated derivatization and analysis of malondialdehyde using column switching sample preparation HPLC with fluorescence detection

Analyte derivatization is advantageous for the analysis of malondialdehyde (MDA) as a biomarker of oxidative stress in biological samples. Conventionally, however, derivatization is time consuming, error-prone and has limited options for automation. We have addressed these challenges for the solid phase analytical derivatization of MDA from small volume tissue homogenate samples. A manual derivatization method was first developed using Amberlite XAD-2 (12 mg) as the solid phase. Subsequently an automated column switching process was developed that provided simultaneous derivatization and extraction of the MDA-DH hydrazone product on a cartridge packed with XAD-2, followed by quantitative elution of the product to an analytical LC column (Waters NovoPak C18, 3.9 x 150 mm). The LOD was 0.02 microg/mL and recovery was quantitative. The method was linear (r(2) >0.999) with precision < 5% from the LOQ (0.06 microg/mL) to at least 35 microg/mL. The method was successfully applied to the analysis of small volume (30 microL) mouse tissue homogenate samples. Endogenous levels of MDA in the tissues ranged from 20 to 40 nmol/g tissue (ca. 0.1-0.2 microg/mL homogenate). Compared to conventional MDA analyses, the current method has advantages in automation, selectivity, precision and sensitivity for analysis from very small sample volumes.