Real-time monitoring of strand-displacement DNA amplification by a contactless electrochemical microsystem using interdigitated electrodes

This paper reports the design and implementation of a contactless conductivity detection system which combines a thermal control cell, a data processing system and an electrochemical (EC) cell for label-free isothermal nucleic acid amplification and real-time monitoring. The EC cell consists of a microchamber and interdigitated electrodes as the contactless conductivity biosensor with a cover slip as insulation. In our work, contactless EC measurements, the effects of trehalose on amplification, and chip surface treatment are investigated. With the superior performance of the biosensor, the device can detect the amount of pure DNA at concentrations less than 0.1 pg μl(-1). The EC cell, integrated with a heater and a temperature sensor, has successfully implemented nicking-based strand-displacement amplification at an initial concentration of 2.5 μM and the yields are monitored directly (dismissing the use of probes or labels) on-line. This contactless detector carries important advantages: high anti-interference capability, long detector life, high reusability and low cost. In addition, the small size, low power consumption and portability of the detection cell give the system the potential to be highly integrated for use in field service and point of care applications.     

Measurement of Compton scattering on bound electrons by the coincidence method

A review of results of the new method for measuring the Compton scattering on bound electrons in germanium, introduced by the presented authors, is given. It is based on the application of two detectors that operate in the coincidence mode. One detector is used as the scatterer and the other as the detector of scattered radiation. Two conditions, simultaneity of pulses from the two detectors and constant energy sum, result in very clean spectra in broad energy regions. Normalization of the Compton spectra to the Ge K X-ray escape peaks, which are measured simultaneously with the Compton spectrum, gives reliable double-differential Compton-scattering cross sections on an absolute scale. Several versions of the impulse approximation are compared to the cross sections obtained by the present method for incident photon energies in the range from 60 to 105 keV. The non-relativistic impulse approximation gives the best agreement to the experimental data. We point out the suitability of the new method for an investigation of the incoherent scattering function at small photon momentum transfer.     

Detectability enhancement of spectrophotometric detectors by the use of multidimensional gas chromatography

Multidimensional gas chromatography (2D GC) is demonstrated as a way to improve limits of detectability of spectrophotometric detectors. UV and IR detectors are generally less sensitive than mass spectrometers or other GC detectors. This has placed some limitations on the useful capabilities provided by spectrophotometric detectors, such as the ability to provide structure‐related information for a particular analyte. In this paper, we report results from interfacing a 2D GC instrument to a UV detector. Symmetry factor and the ratio of retention time divided by peak width did not show deterioration of the quality of chromatography when a megabore column was used with this detector. Furthermore, an increase in the limits of detectability over that attainable in a single‐column system was realized by using the 2D GC system. However, the low flow (1 mL/min) imposed by the use of a microbore column (250 μm ID) caused significant tailing when the UV detector was used.     

Comparison of the response of four aerosol detectors used with ultra high pressure liquid chromatography

The responses of four different types of aerosol detectors have been evaluated and compared to establish their potential use as a universal detector in conjunction with ultra high pressure liquid chromatography (UHPLC). Two charged-aerosol detectors, namely Corona CAD and Corona Ultra, and also two different types of light-scattering detectors (an evaporative light scattering detector, and a nano-quantity analyte detector [NQAD]) were evaluated. The responses of these detectors were systematically investigated under changing experimental and instrumental parameters, such as the mobile phase flow-rate, analyte concentration, mobile phase composition, nebulizer temperature, evaporator temperature, evaporator gas flow-rate and instrumental signal filtering after detection. It was found that these parameters exerted non-linear effects on the responses of the aerosol detectors and must therefore be considered when designing analytical separation conditions, particularly when gradient elution is performed. Identical reversed-phase gradient separations were compared on all four aerosol detectors and further compared with UV detection at 200 nm. The aerosol detectors were able to detect all 11 analytes in a test set comprising species having a variety of physicochemical properties, whilst UV detection was applicable only to those analytes containing chromophores. The reproducibility of the detector response for 11 analytes over 10 consecutive separations was found to be approximately 5% for the charged-aerosol detectors and approximately 11% for the light-scattering detectors. The tested analytes included semi-volatile species which exhibited a more variable response on the aerosol detectors. Peak efficiencies were generally better on the aerosol detectors in comparison to UV detection and particularly so for the light-scattering detectors which exhibited efficiencies of around 110,000 plates per metre. Limits of detection were calculated using different mobile phase compositions and the NQAD detector was found to be the most sensitive (LOD of 10 ng/mL), followed by the Corona CAD (76 ng/mL), then UV detection at 200 nm (178 ng/mL) using an injection volume of 25 μL.     

多荧光光纤传感器及其在混合溶剂检测中的应用

微纳光纤与其他微纳结构的集成可以拓展荧光光纤传感器检测范围和集成度,是光纤传感领域的研究热点。目前,国际上关于荧光光纤传感器这一领域的研究还处于单一检测物荧光响应的阶段,对多检测物的多通道荧光响应仍存在很大挑战。本文结合微纳光纤的光波导性能以及有机荧光材料的光功能特性,制备了能够同时激发和收集多种荧光的微纳光纤,并将之应用于高性能荧光光纤传感器的制备。通过选用不同荧光波长的有机材料与凝胶掺杂,制备了多荧光发射的光纤涂层材料,可控构筑了多组分荧光检测剂掺杂凝胶涂层。利用荧光光谱结合色度图分析,确定检测物与色坐标的关系,实现了多检测物的多通道荧光响应,为实现多荧光光纤传感器的可控构筑提供了有益的借鉴和指导意义。     

Ultra-sensitive UV detection in micro separation

Most UV detectors used in micro separation techniques today suffer from an enormous loss in sensitivity due to the small cell volume necessary to avoid peak dispersion. Flow cells with volumes between 10-100 nl are normally constructed of fused silica tubing. With typical path lengths of between 50-320 μm, a tremendous loss in sensitivity results, consistent with Beer-Lambert's law. We have successfully constructed an ultrasensitive UV flow cell. Its total volume does not exceed 90 nl and yet its optical path length is nearly 2 cm (20,000 μm). Due to its special design, dead volume is minimized and is comparable to that of a 3 nl capillary flow cell (on-column). Sensitivity enhancement of 100-500 times can easily be realized in comparison with on-column detection. The potential of this ultra-sensitive UV flow cell in micro separations is illustrated by applications using Capillary LC and Pakked Capillary SFC.     

Detection limits of thermal conductivity and photoionization detectors in high speed narrow bore CGC

Not only the required input band width and the availability of compatible instrumentation limit the reduction of column diameter but so do the column sample capacity and detector characteristics, such as volume and sensitivity. In this paper the scope and limitations of thermal conductivity and photoionization detection at atmospheric and reduced pressures for capillary gas chromatography are discussed at length. It is shown that the sensitivity of a thermal conductivity detector is inversely proportional to the pressure. Reduction of cell volume and decrease of pressure appear equivalent with respect to minimum detectable amount and peak broadening. This results in femtogram detection limits for column diameters as low as 10 μm. For photoionization detectors the sensitivity did not improve at reduced pressures, so that the effect of reduced pressure and addition of make-up gas on the detection limits is the same. Nevertheless, the applicability of a low volume photoionization detector (40 μl) for capillary columns with a diameter as low as 50 μm will be demonstrated by series coupled PID and FID detectors and illustrated with various applications.     

The Effects of the Electrode System Geometry on the Properties of Contactless Conductivity Detectors for Capillary Electrophoresis

The basic analytical parameters of contactless conductivity detectors with planar, semi‐tubular and tubular electrodes have been compared. It has been found that the differences in the analytical parameters of the detectors are not significant for analytical use. The mean values of baseline peak‐to‐peak noise of 0.27, 0.35 and 0.33 mV, sensitivities of 0.97, 2.08 and 2.27 mV/pg (for K⁺ ion), limits of detection of 0.93, 0.65 and 0.53, and the heights equivalent to a theoretical plate of 2.83, 2.39 and 2.40 μm were obtained for the detectors with planar, semi/tubular and tubular electrodes, respectively. Modifications of the basic detectors, namely a detector with thinned capillary wall and planar electrodes, and a detector with semi‐tubular electrodes placed one against the other on the opposite sides of the capillary were also tested. The configuration with the electrodes placed one against the other permits detector construction with zero gap between the electrodes without increasing the noise; when the electrodes overlap, the detector begins to operate as a permittivity detector.     

Gas chromatographic applications with the dielectric barrier discharge detector

With gas chromatography, there are many more choices for detectors when compared to other separation disciplines in analytical chemistry. The presence of sensitive and selective detectors aids in easing the separation requirements imposed on the capillary column. The current gas phase detectors, however, do not completely fulfill contemporary analytical needs. One example is in the area of ultratrace analysis of permanent gases for semiconductor industry. Another example is in the area of environmental/industrial hygiene monitoring for compounds such as 1,3-butadiene or vinyl chloride. The dielectric barrier discharge detector, a new highly sensitive detector with tuneable selectivity, has recently been innovated and commercialized. In this paper, the principle of operation of the detector, along with critical challenging industrial applications such as the analysis of oxygenated compounds, sulfur-containing compounds, and other compounds of industrial significance is presented.     

一种基于双工作电极-双通道的毛细管电泳电化学检测系统

报道了一种双工作电极-双通道毛细管电泳电化学检测系统，实现电导和安培 同时检测或者安培与安培检测联用，使两种方法相互补充，发挥各自的优势。其中 ，工作电极与检测池的制作工艺简单，操作简便，通过不锈钢针管和毛细管作为套 管，无需三维微调装置即可简单实现双工作电极的准确放置及分离毛细管与工作电 极的准确对接，并根据分析体系的需要采用不同类型的工作电极和检测器；同时采 用复式滤波电路解决了不同检测器之间的电场叠加对输出信号的干扰问题。采用该 装置可以同时检测复杂体系中的电活性和惰性物质，或同时测定只能氧化或只能还 原的物质，还可以对具有氧化还原性质的物质进行纯度的确证。将该装置应用于实 际样品的测定，节约了分析时间，提高了分析速度，扩大了检测范围，结果令人满 意。     

Practical method for evaluation of linearity and effective pathlength of on-capillary photometric detectors in capillary electrophoresis

The optical characteristics of on-capillary photometric detectors for capillary electrophoresis were evaluated and five commercial detectors were compared. Plots of sensitivity (absorbance/concentration) versus absorbance obtained with a suitable testing solution yield both the linear range and the effective path length of the detector. The detector linearity is a crucial parameter when using absorbing electrolytes, such as for indirect photometric detection, and especially for highly absorbing electrolyte probe ions. The upper limits of the linear ranges (determined as 5% decline in sensitivity) for five commercial detectors ranged from 0.175 to 1.2 AU. The effective pathlength reflects the quality of the optical design of the detector and is equal to the capillary internal diameter only for a light beam passing exactly through the capillary centre, but becomes progressively shorter for imperfect optical designs. The determined effective pathlength for the five investigated detectors ranged from 49.7 to 64.6 microm for a 75 microm I.D. capillary.     

Spectroelectrochemical detector for flow-injection systems and liquid chromatography

Flow-through spectroelectrochemical detectors for flow-injection systems and liquid chromatography are described. The detectors have a rectangular flow channel with a reticulated vitreous carbon working electrode followed by an open optical window. The dead volumes of the cells are 27 μl (liquid chromatography) and 80 μl (flow injection). In situ spectral monitoring of reaction products and intermediates for compounds that are both weakly and highly absorbing is demonstrated by using o-tolidine and N,N,N′,N′-tetramethyl-p-phenylenediamine. As a detector for flow-injection systems, components in two-component mixtures can be quantified. As a detector for liquid chromatography, simultaneous absorbance and electrochemical chromatograms allow more eluting compounds to be identified and quantified. Mixtures of nitro- and chloro-phenols are used to illustrate the simultaneous profiling of spectral and redox properties.     

Copolymer solutions as separation media for DNA capillary electrophoresis

Capillary electrophoresis techniques offer high plate numbers and are highly suited for the efficient separations of a wide variety of chemical components in diverse matrices. Because of the small capillary and detection cell dimensions, together with the minute volumes of samples to be injected, sensitive detection schemes based on different physicochemical principles are being developed. One logical approach to increased sensitivity in capillary electrophoresis detection has been the development of chemiluminescence-based detectors. The development of on-line ultrasensitive chemiluminescence detection (referred to the concentration detection limit of nM order of magnitude or mass detection limit of amol order of magnitude) in capillary electrophoresis system is reviewed. The applications and limitations of the current detection methodology are briefly considered and future prospects for the development are discussed.     

Application of an asymmetric flow field flow fractionation multi-detector approach for metallic engineered nanoparticle characterization--prospects and limitations demonstrated on Au nanoparticles

In this work we discuss about the method development, applicability and limitations of an asymmetric flow field flow fractionation (A4F) system in combination with a multi-detector setup consisting of UV/vis, light scattering, and inductively coupled plasma mass spectrometry (ICPMS). The overall aim was to obtain a size dependent-, element specific-, and quantitative method appropriate for the characterization of metallic engineered nanoparticle (ENP) dispersions. Thus, systematic investigations of crucial method parameters were performed by employing well characterized Au nanoparticles (Au-NPs) as a defined model system.For good separation performance, the A4F flow-, membrane-, and carrier conditions were optimized. To obtain reliable size information, the use of laser light scattering based detectors was evaluated, where an online dynamic light scattering (DLS) detector showed good results for the investigated Au-NP up to a size of 80 nm in hydrodynamic diameter. To adapt large sensitivity differences of the various detectors, as well as to guarantee long term stability and minimum contamination of the mass spectrometer a split-flow concept for coupling ICPMS was evaluated. To test for reliable quantification, the ICPMS signal response of ionic Au standards was compared to that of Au-NP. Using proper stabilization with surfactants, no difference for concentrations of 1–50 μg Au L⁻¹ in the size range from 5 to 80 nm for citrate stabilized dispersions was observed. However, studies using different A4F channel membranes showed unspecific particle–membrane interaction resulting in retention time shifts and unspecific loss of nanoparticles, depending on the Au-NP system as well as membrane batch and type. Thus, reliable quantification and discrimination of ionic and particular species was performed using ICPMS in combination with ultracentrifugation instead of direct quantification with the A4F multi-detector setup.Figures of merit were obtained, by comparing the results from the multi detector approach outlined above, with results from batch-DLS and transmission electron microscopy (TEM). Furthermore, validation performed with certified NIST Au-NP showed excellent agreement. The developed methods show potential for characterization of other commonly used and important metallic engineered nanoparticles.     

二元复杂共混体系组成的SEC-LS分析

提供了一种利用体积排阻色谱-光散射(SEC-LS)联用技术来解决二元复杂共混体系组成的定量分析问题.基于体积排除色谱的绝对定量化原则,首先从理论上分析了共混物的光散射响应因子与组成呈线性关系.通过分析六组复杂共混体系的光散射响应因子与组成的关系,验证了该线性关系确实存在.进而利用该线性关系计算了共混体系的组成.在某些共混体系中,通过光散射响应因子得出的组成比利用示差法得出的组成更加接近原料组成.通过分析这两种方法产生误差的来源,阐述了产生该现象的原因.     

Development of high efficiency, multi-element CdZnTe detectors for portable measurement applications

We describe the development of detector arrays and electronics for large-volume, hand-held CdZnTe detectors with the same counting efficiency as portable NaI(Tl) detectors presently used for nuclear material measurement applications. The pulse-height resolution of the multi-element detectors is at least three times better than NaI(Tl) over a wide energy range (from 100 keV to several MeV), enabling more accurate measurements of gamma-rays emitted by special nuclear material. Arrays of up to eight coplanar grid detectors can be combined to make detectors ranging in size from 4 to 14 cm³. Because the number of spectroscopy channels is small, low-power, hand-held detectors can be manufactured with conventional printed circuit board technology, thus keeping the cost of multi-element detectors to a minimum. The design and performance of an 8-element detector is presented.     

Property of TS-16N solid state nuclear track detectors as an imaging medium for macroautoradiography of alpha-emitters in biological specimens

Feasibility of TS-16N solid state nuclear track detectors for an imaging medium of rapid autoradiography of alpha-emitters is described. Though a little longer etching time was required, the contrast of autoradiographic image on this detector proved to be superior to CR-39 detectors whose property for macroautoradiography was previously reported by the authors. The resolutions of these two different type detectors were almost equivalent to each other. The autoradiography taken by way of trial proved that this detector could be used to study metabolism and dosimetry of internally deposited alpha-emitters. With further study, the inherent properties of this detector such as low background or high sensitivity should extend the field of track etch imaging technique such as fast neutron radiography.     

A New Dual-electrode and Multi-channel Electrochemical Detection System for Capillary Electrophoresis

A new type of dual-electrode and multi-channel electrochemical detection technology for capillary electrophoresis is described in this paper.Two detectors(the amperometric detector and the conductometric detector) or two conductometric detectors are connected to the same capillary electrophoresis system.The whole system possesses the advantages of the two electrochemical detectors including sparing time,improving the analytical speed and expanding the sample range.The working electrode and detector cell are handled easily.The system was applied to sample detection with satisfactory results.     

毛细管电泳光学检测器的进展

对毛细管电泳的光学检测器作了简要评述。根据所采用的检测原理。光源检测器可分为紫外检测器，激光诱导荧光检测器、化学肆光检测器、荷耦合器件检测器、折射指数检测器等许多种类，具有简单方便、使用广泛，信息量较大等特点，是一类有良好诉检测器。