用于测量亚硝酸的长光程吸收光谱仪的研制

基于湿化学采样及光学检测的方法,自行搭建了长光程吸收光谱仪(LOPAP)用于检测痕量的亚硝酸.该仪器成本低,响应时间快,灵敏度高,检测限低,可以连续测量并且排除了现有其他仪器存在干扰影响的问题,既能够对大气中的痕量亚硝酸进行测量,又能检测例如烟雾箱和废气中高浓度的亚硝酸.该仪器采用双通道系统,通过将两个通道测量信号相减可以减小测量中未知干扰物的影响.仪器的检测限可以达到9×10-12mol·mol-1,响应时间为5 min,其准确度为±10%.另外对NO、NO2、O3、NO2+O3、NO2+SO2、O3+HONO等气体进行了仪器的干扰分析,发现只有当NO2存在时才有很弱的HONO干扰信号产生,干扰值大约为0.02%.同时在2013年8月29日到9月4日对HONO在中国科学院化学研究所进行了为期六天的外场观测,分析了HONO的日浓度变化,以及这种变化与光照强度、NOx浓度和NO2浓度之间的关系.HONO/NO2的比率表明除了NO2的非均相反应外还存在未知来源.     

Ferric metal-organic framework for microwave absorption

In this study, we have shown for the first time that ferric metal-organic framework (Fe-MOF) has the ability to attenuate gigahertz-range electromagnetic radiation through means of a novel interference mechanism. A large reflection loss value of ?54.2 dB can be obtained, equivalent to over 99.999% absorption efficiency. The microwave absorption performance is largely dependent on the dielectric permittivity and magnetic permeability properties. The electrical loss ratio tgδ_ε increases with the frequency from 0.13 at 1.0 GHz to 0.69 at 18.0 GHz, while the magnetic loss ratio tgδ_μ is only between 0.05 and 0.14. The conductivity σ increases with the frequency from 0.08 S/m at 1.0 GHz to 5.24 S/m at 18.0 GHz, while the skin-depth δ decreases with the frequency. The thickness (d) of the absorber is inversely proportional to the reflection loss peak value (RL_peak), the reflection loss peak frequency (f_peak), and the critical reflection loss peak width (Δf₁₀). The non-zero magnetic susceptibility (χ) accelerates the shift of f_peak to lower values as d grows bigger; however, it improves the RL_peak value and larger microwave absorption efficiency and reduces the quick narrowing of the critical frequency range. The microwave performance of Fe-MOF is likely related to its microwave conductivity, which may originate from the polar rotations in the interface or defects. A new mechanism is proposed for the large reflection loss based on the interference of the reflected microwave from the front and back surface of the microwave absorber, especially when the thickness matches with the odd integer values of the wavelength.     

内窥式扫频光源光学相干层析系统的探头设计

利用自聚焦透镜和单模光纤搭建了基于光纤旋转连接器的内窥式扫频光源光学相干层析成像系统.利用Zemax模拟了内窥探头的光学性能,分析了光纤到自聚焦透镜的距离和自聚焦透镜节距对探头性能参量的影响.在综合考虑元器件成本以及成像要求后,选择无需定制,节距为0.24Pitch的自聚焦透镜,确定光纤与自聚焦透镜之间的距离为0.7mm.经实验测得该系统的横向分辨率约为19.5μm,纵向分辨率约为9μm,工作距离约为7mm,成像深度为6.2mm(空气中),与理论值接近.为了验证该系统对生物组织的成像性能,利用该系统对猪食道进行离体成像,重建后的层析图中可以明显地观察到猪肠道的表皮层和固有层.测量系统的各项成像性能参量以及对生物组织的成像性能表明该探头在内窥成像中是可行的.     

Effective arsenic removal using polyacrylonitrile-based ultrafiltration (UF) membrane

Applicability of polyacrylonitrile (PAN)-based negatively charged ultrafiltration (UF) membrane for effective arsenic removal has been demonstrated, to our knowledge, for the first time. The hydrolysis of PAN-based UF membrane surface by NaOH leading to the formation of carboxylate (COO⁻) groups and reduction in initial pore size rendered As-V rejection capability by Donnan exclusion principle. A lowering in pore size was indicated by the reduction in water flux and elevation in rejection of protein and polyethylene glycol (PEG). NaOH treatment leading to formation of carboxylate group on the membrane surface was indicated by FTIR-ATR, while contact angle measurement indicated increased hydrophilicity. This treatment rendered membrane surface smoothening as confirmed by SEM and AFM analyses. The molecular weight cut off after the NaOH treatment was found to be 6 kDa. The rejection of pentavalent arsenic (As-V) by these surface modified membranes was studied with different feed concentration, cross-flow velocity, pressure, temperature and pH. Experiments with 50 ppb As-V in feed showed that arsenic rejection was close to 100% and remained constant up to 6 h. Feed sample concentration of 1000 ppb and 50 ppm of As-V showed >95% rejection at pH 7 and room temperature, but for 1000 ppm feed concentration, the rejection was 40–65%. For concentrations ≤50 ppm of arsenic in the feed, the rejection coefficient was not dependent on cross-flow velocity or transmembrane pressure. The rejection for 1000 ppm concentration of As-V varied from 40 to 65% with variation in the cross-flow velocity and transmembrane pressure as the concentration polarization was important.     

Achievements in resonance Raman spectroscopy review of a technique with a distinct analytical chemistry potential

In an extended introduction, key aspects of resonance Raman spectroscopy (RRS) such as enhanced sensitivity and selectivity are briefly discussed in comparison with normal RS. The analytical potential is outlined. Then achievements in different fields of research are highlighted in four sections, with emphasis on recent breakthroughs: (1) The use of visible RRS for analyzing carotenoids in biological matrices, for pigments and dyes as dealt with in art and forensics, and for characterizing carbon nanotubes. (2) The use of RRS in the deep UV (excitation below 260 nm) in the bioanalytical and life sciences fields, including nucleic acids, proteins and protein-drug interactions. Metalloproteins can be studied by visible RRS in resonance with their chromophoric absorption. (3) Progress in theoretical calculations of RRS excitation profiles and enhancement factors, which ultimately might facilitate analytical RRS. (4) Instrumental and methodological achievements including fiber-optic UV-RRS, coupling of RRS to liquid chromatography and capillary electrophoresis. Sensitivities can approach the single-molecule level with surface-enhanced RRS or tip-enhanced RRS. Last but not least, promising fluorescence background rejection techniques based on time-gated detection will be presented. This review ends with a concluding section on future expectations for RRS, in particular its potential as an analytical technique.     

A novel method for determination of low molecular weight dicarboxylic acids in background atmospheric aerosol using ion chromatography

This paper describes a novel gradient elution ion chromatographic method using a Dionex AS11 system for the determination of low molecular weight dicarboxylic acids (low-M_w DCAs) in background atmospheric aerosol. Interference with the oxalic acid peak from sulfate in background PM_2.5 aerosol, 15.8 times the oxalic acid concentration, was remedied by removing sulfate using a barium cartridge, whilst interference with the malonic acid peak from carbonate was reduced by using a carbonate removal device. An alternative remedy to sulfate interference was use of an AS14 system using isocratic eluent, and this produced good resolution of oxalic acid from a high sulfate peak. In both the AS11 and the AS14 system, linear correlation coefficients were at all times >0.9990 with excellent linear range, the recoveries ranged from 92.8 to 106%, with relative standard deviation of 3.67-6.30%, whilst method detection limits (MDLs) ranged from 0.36 μg L⁻¹ for malic acid to 3.87 μg L⁻¹ for maleic acid. These data indicate that the analytical methods developed herein produce excellent separation efficiency and good determination of low-M_w DCAs with satisfactory accuracy, recoveries, and MDLs. Samples left at room temperature (20 °C) for 300 min in a simulation of the ‘waiting time’ involved in the proposed IC analysis decayed to between 86% (oxalic acid) and 39% (succinic and malonic acids) of their original concentration, whilst at 4 °C concentrations remained at 96-101% of original, indicating that maintaining samples at a low temperature prior to injection into the IC analyzer is vital for obtaining accurate results when analyzing low-M_w DCAs. Oxalic acid was found to be the most prevalent low-M_w DCA in background aerosol, comprising 57% of the total low-M_w DCAs and 0.959% of the PM_2.5 aerosol mass, followed by succinic acid and malonic acid.     

SECM visualization of the spatial variability of enzyme-polymer spots. 3. Enzymatic feedback mode

The responses of a PQQ-GDH entrapped in a polymer structure to mixtures of glucose and maltose were evaluated. Each compound was considered in the concentration range of 0–0.2 mM. Imaging was performed at constant height in the enzymatic feedback mode of scanning electrochemical microscopy (SECM). The enzyme-polymer spot was discretized into 15 × 15 μm² substructures which were treated as independent individual microsensors. The response surfaces of the individual microsensors were approximated with a linear regression model. The coefficients in the derived equations represent contributions from topography, glucose concentration, maltose concentration, and the competition of glucose and maltose for the same active site of PQQ-GDH to the measured signal. The ratio of glucose and maltose contributions to the current at the SECM tip was constant for all microsensors and it was predominantly determined by the ratio of the turnover rates of both analytes in the PQQ-GDH catalyzed reaction. Using the difference between these coefficients, it was possible to select the microsensors within the overall enzyme-polymer spot that provided the best data for quantifying glucose and maltose by the artificial neural network used. The quantification of glucose and maltose was successful, except when the contributions from the components of the mixture were n _g =k n units of glucose and simultaneously n _m = 1.86(1−k)n units of maltose, for each constant n > 0 and k∈<0,1>.     

Reduction of the interferences of biochemicals and hematocrit ratio on the determination of whole blood glucose using multiple screen-printed carbon electrode test strips

A practical approach to reduce the interferences of biochemicals and hematocrit ratio (Hct%) in the determination of whole blood glucose using multiple screen-printed carbon electrode (SPCE) test strips is described. SPCE test strips with and without glucose oxidase [i.e., GOD(+)-SPCEs and GOD(-)-SPCEs] were used and the chronoamperometric currents of test glucose solutions with various spiked uric acid concentrations and Hct% were measured. By establishing the interference relationships between glucose concentrations and uric acid concentrations as well as Hct% values and with appropriate corrections, the whole blood glucose determinations could be made to be more accurate and comparable to those determined by the reference YSI method. Specifically, the use of the ΔI value, i.e., the current difference between GOD(+)-SPCE and GOD(-)-SPCE measurements, would reduce most of the uric acid/biochemical interferences. An interpolation method was also established to correct for the glucose determinations with Hct% interferences. The Hct% corrections using the interpolation method are especially important and necessary for those blood samples with glucose concentrations higher than 110 mg dL^-1 and Hct% values lower than 35%. This approach should also be applicable to other biochemical determinations using similar electrochemical techniques. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

基于数学形态学的声纳主动探测信息净化方法

针对主动声呐探测画面中混响和被动条状干扰问题,提出了一种基于数学形态学滤波的主动探测信息净化方法。该算法通过研究数学形态学滤波器的频响特性,构造与主动声呐探测画面中目标频率特性匹配的结构元素,然后对主动声呐探测画面进行形态学滤波处理,估计主动声呐探测画面的干扰背景,最后进行探测信息净化,并利用形态学滤波对净化后图像进行增强。海试数据处理结果表明,该文方法能够有效抑制低频被动条状干扰以及混响背景,使点状目标在图像中表现更为明显,更有利于目标检测。