Bedeutung der GC-Detektoreigenschaften

Ohne Zusammenfassung

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Detector comparison for sulfur and chlorine detection with laser induced breakdown spectroscopy in the near-infrared-region

Laser-induced breakdown spectroscopy has been employed for the investigation of the sulfur and chlorine content of building materials. Both, chloride and sulfate ions are major damaging species affecting the stability and lifetime of a structure. Chlorine and sulfur are mostly detected in the VUV and the NIR. In case of building materials the main elements like calcium or iron have many strong spectral lines over the whole spectral range, so that trace elements can only be detected in spectral windows unaffected from these lines. With regard to a preferably simply, robust against dust and vibrations and portable setup only the NIR spectral features are used for civil engineering applications.

Most detectors, mainly CCD cameras have rapidly decreasing quantum efficiency in the NIR. Also the quantum efficiency of the photocathode of CCD-Detectors with image intensifier is decreasing in the NIR. Different CCD-detectors were tested with respect to high quantum efficiency and high dynamic range, which is necessary for simultaneous detection of weak spectral lines from trace elements and intense spectral lines from main elements.

The measurements are made on reference samples consisting of cement, hydrated cement, cement mortar and concrete with well-defined amounts of the trace elements. Experimental conditions are chosen for an optimum intensity of the trace element spectral lines. The detector systems are compared by limit of detections and the signal to noise ratio.     

Simultaneous multichannel mass-specific detection for high-performance liquid chromatography using an array detector sector-field mass spectrometer

The use of a separation step, such as liquid chromatography, prior to inductively coupled plasma mass spectrometry (ICP–MS) has become a common tool for highly selective and sensitive analyses. This type of coupling has several benefits including the ability to perform speciation analysis or to remove isobaric interferences. Several limitations of conventional instruments result from the necessity to scan or pulse the mass spectrometer to obtain a complete mass spectrum. When the instrument is operated in such a non-continuous manner, duty cycle is reduced, resulting in poorer absolute limits of detection. Additionally, with scanning instruments, spectral skew can be introduced into the measurement, limiting quantitation accuracy. To address these shortcomings, a high-performance liquid chromatograph has been coupled to an ICP–MS capable of continuous sample introduction and simultaneous multimass detection. These features have been realized with a novel detector array, the focal plane camera. Instrument performance has been tested for both speciation analysis and for the elimination of isobaric interferences. Absolute limits of detection in the sub picogram to tens of picograms regime are obtainable, while the added mass dimension introduced by simultaneous detection dramatically increases chromatographic peak capacity.     

The MPE/UCB far-infrared imaging Fabry-Perot interferometer (FIFI)

FIFI is an imaging spectrometer with two or three Fabry-Perot interferometers (FPI) in series for airborne astronomical observations in the far-infrared range (=40...200m). It employs 5×5 arrays of photoconducting detectors and offers spectral resolutions as small as 2km/s. Resolution and bandwidth can be set over a wide range to match a variety of astronomical sources. Cryogenic optics minimizes thermal background radiation and provides for in-flight step tunable spatial resolution. At 158 m wavelength the background-limited NEP is 3 × 10^-15W/Hz at 40 km/s resolution and with two FPI's; with three FPI's the expected NEP is 10^-15WHz at 5 km/s resolution.The frequency-chopping mode of the high-resolution Fabry-Perot allows for line detection in extended objects. Absolute internal flux calibration ensures adequate flat fielding of the array elements.     

Linearity in output signal of optical position-sensing detector systems

A precise operation of the position-sensing detectors (PSD) is exploited in this study. A position-sensing detector is modeled and the amplified output signal for this device as a result of input source current variation is studied. Beam displacement on such detectors is calculated and approximated and more accurate expressions for the generated signals are obtained. Linearity effect in output response of such a device is also investigated. The expansion coefficients for the signals are determined, which show the effect of the nonlinear terms. The first nonlinear coefficient is about 16.6% of the linear coefficient while the next terms are 2.5, 0.89, and 0.48% of the linear coefficient, respectively. For a position change of x=0.2 unit the linear term is 0.08, the third-order term −0.005328, and the fifth-order term is only about 0.000032, which is negligible. To see the operational result, using software simulates a PSD and the related circuit that provides the positional information.     

探测器点阵法测量激光光斑参数的仿真

 仿真分析了用均匀分布的探测器点阵测量激光光斑方法中，探测器灵敏度的线性工作动态范围，灵敏度的一致性差异，点阵间距等参数和光斑质心位置的测量误差，光束总能量的测量误差，以及光斑的分布等。仿真结果表明，当探测器灵敏度的一致性差异小于10％，线性工作范围的动态范围大于30dB，点阵间距小于光斑直径的1/5时，光束总能量的误差小于6％，光斑质心位置的测量误差小于光斑直径的2％，拟合的光斑分布和实际光斑分布比较接近。     

Monte Carlo simulation of radon SSNT detectors

A Monte Carlo based software for the computation of the sensitivity of etched radon track detectors was developed. It can be applied to the measurement of radon and radon daughters in free air or inside of a measurement chamber. LR 115 and CR-39 detectors, with or without an attenuator, are specifically addressed. Various etching conditions and observation criteria for counting the track density may be specified. The latent track formation and the etching process are realistically modelled. The dependence of the etch-rate ratio on the energy is taken into account. The plate-out phenomenon is included in the model. An inhomogeneous source distribution in the detector cup can be considered.     

进口原油、天然气检验监管的安全、环保和反欺诈技术

讨论了进口原油和天然气检验监管工作、包括科研工作重点应该转移到从安全、环保、卫生、反欺诈等方面把好国门的必要性和紧迫性。提出了加快研制和开发现场、快速、高通量检测仪器、装置和传感器等建议。     

Research on mechanism for high light absorption of micro-structured silicon

The mechanism of the high light absorption of surface-microstructure silicon is discussed using optical simulation based on Monte Carlo method in this article. Calculation results indicate that the micro-structured surface and high refractive index of material are the two key factors that effectively reduce the reflection, especially transmittance, of the material instead of surface wave and sulfur. In addition, this shows clearly a development in direction for manufacturing new type detectors and increasing the efficiency of traditional detector effectively in the future.     

Fullerene‐Crown Ether Coated Piezoelectric Crystal Liquid Chromatographic Detector for Metal Ions and Polar/Nonpolar Organic Molecules

Fullerene(C60)‐dibenzo‐16‐crown‐5‐oxyacetic acid (DBI6C5‐OCH₂‐COOC₆₀) was prepared and applied as the coating material on piezoelectric quartz crystals for detection of various metal ions and polar/nonpolar organic molecules. The C60‐crown ether‐coated piezoelectric crystal sensor with a home‐made computer interface for signal acquisition and data processing was applied as an ion chromatographic (IC) detector for various metal ions, e.g., alkali metal, alkaline earth metal and transition‐metal ions. The piezoelectric detector exhibited quite good sensitivity of 10⁴ ～ 10⁶ Hz/M and good detection limit of 10^?3 ～ 10^?4 M for these metal ions. The C60‐crown ether piezoelectric detector compared well with the commercial conductivity detector conventionally used for metal ions. The ionic size and ionic charge seemed to have significant effect on the frequency response of the piezoelectric detector. The C60‐crown ether coated piezoelectric crystal sensor was also employed as a high performance liquid chromatographic (HPLC) detector for various polar organic molecules with frequency responses in the order: amines > carboxylic acids > alcohols > ketones. Furthermore, nonpolar organic molecules, e.g., n‐hexane, 1‐hexene and 1‐hexyne, were also detected with this piezoelectric crystal detector. The frequency responses of the piezoelectric crystal detector for these nonpolar organic molecules were in the following order: alkynes > alkenes > alkanes. The effects of solvents and flow rate on the frequency responses of the piezoelectric crystal detector were investigated. The C60‐crown ether coated piezoelectric crystal detector also showed short response time (< 1 min.) and good reproducibility.