COMPARISON TABLE OF THE PERFORMANCE OF TWENTY-FIVE TYPES OF RADIATION DETECTOR

Abstract. The paper reviews some of the difficulties associated with intercomparing the performances of different types of radiation detector, and discusses the best form of figure of merit to apply to a wide variety of detector types. A table gives current data on the best performance achieved by twenty-five basic types of radiation detector. in terms of spectral response, usable frequency range, spatial resolution (where appropriate) and sensitivity. Sensitivity is listed under two headings: the minimum detectable signal, expressed in fundamental units (watts, watt cm-³, joules or joules cm^-2); and the output sensitivity, which indicates the kind and magnitude of output, and which is accordingly expressed in practical units. Source references are given to cover all detector types listed.     

Detection efficiency calculations using Geant4 for a broad-energy germanium gamma spectrometer

In assistance of radionuclide measurements at Canada’s Comprehensive Nuclear-Test-Ban Treaty (CTBT) laboratory, a Geant4 Monte Carlo application has been developed in simulating a broad-energy germanium detector and calculating detection efficiencies. The detector model was optimized in a reliable and non-biased manner through simultaneous tuning on gap distance and detector dimension, and was validated over various realistic measurement scenarios. All work is based on a series of experiments which covers the typical energy range of gamma radiation in environmental analysis, and considers the variety of the CTBT sample type, dimension and distance-to-detector. In all cases, the predicted efficiencies are consistent with the empirical ones within 5%, with a typical deviation of 3% in majority.     

Multi-element determinations of trace elements in glass by instrumental photon activation analysis

An instrumental photon activation method is reported for multi-element determinations in glass. The concentrations of 17 elements in NBS standard glass can be determined by irradiation with 30-MeV bremsstrahlung and measurement of the resulting γ-rays with a Ge(Li) detector. The average of all relative standard deviations is 2.7%; the relative deviations from the NBS certified values range from 1.4 to 3.4%.     

Non-dispersive atomic fluorescence spectrometry with a carbon filament atom reservoir

The non-dispersive atomic fluorescence spectrometric determination of Bi, Cd, Hg, Te, Tl and Zn on a carbon filament atom reservoir with electrodeless discharge lamp sources and reflecting microscope objective lenses is described. The non-dispersive system shows distinct advantages for an element such as tellurium whose principal fluorescence lines fall within the useful range of the solar-blind photomultiplier detector, and marginal advantages for mercury, cadmium and zinc where only one line is within the detector range. It is inferior for bismuth, thallium and lead where lines lie at the extremes of the useful detector range. The technique was applied successfully to the determination of cadmium (0.012%) in a copper-base alloy.     

A Piezoelectric Crystal Detector for Acetoin

Abstract

A piezoelectric quartz crystal coated with tetrabutyphosphoniun chloride was found to be a good detector for acetoin. The coating is sensitive in the ppb range and completely reversible. The response curve is linear over a concentration range of 8-120 ppb. The detector can be tuned to give a satisfactory response in 30 seconds.     

A New Polarographic Flow-Through Detector

Abstract

The construction of a flow-through polarographic detector is described, based on introduction of the test solution into a space filled with mercury. Two variants of the detector have been developed, with the inlet jet placed vertically and horizontally. The dynamic properties of the two detector variants, the linear dynamic range and the response reproducibility were tested using o-nitrophenol as a model substance. The detector with the vertical jet has a wide linear dynamic range and that with the horizontal jet exhibits an extremely rapid response with a time constant of the order tenths of a second.     

Comparison of different detectors for amino acid analysis

Summary Three different detectors for gas chromatography are compared in respect to sensitivity and selectivity: the flame-ionization detector, the nitrogen-selective alkali-flame ionization detector and the electron-capture detector. Their suitability for amino acid analysis is discussed, especially concerning sensitivity and linearity of detection. The nitrogen-selective detector proved to be most suitable both in respect to sensitivity and selectivity. The detection limit is in the range of less than 1 pg using the nitrogen-selective detector, about 1 – 2 pg with the electron-capture detector and about 5 –15 pg using the flame-ionization detector.

---

Vergleich verschiedener Detektoren für die Analyse von Aminosäuren

     

Six orders of magnitude dynamic range in capillary electrophoresis with ultrasensitive laser-induced fluorescence detection

An ultrasensitive laser-induced fluorescence detector was used with capillary electrophoresis for the study of 5-carboxy-tetramethylrhodamine. The raw signal from the detector provided roughly three orders of magnitude dynamic range. The signal saturated at high analyte concentrations due to the dead time associated with the single-photon counting avalanche photodiode employed in the detector. The signal can be corrected for the detector dead time, providing an additional order of magnitude dynamic range. To further increase dynamic range, two fiber-optic beam-splitters were cascaded to generate a primary signal and two attenuated signals, each monitored by a single-photon counting avalanche photodiode. The combined signals from the three photodiodes are reasonably linear from the concentration detection limit of 3 pM to 10 μM, the maximum concentration investigated, a range of 3,000,000. Mass detection limits were 150 yoctomoles injected onto the capillary.     

Development of a polypyrrole-based amperometric detector for the determination of certain anions in water samples

The development of a polypyrrole-based modified electrode for use in the detection of anions in flow-injection analysis and ion chromatography is described. Chloride, nitrate, nitrite, perchlorate, bromide, carbonate, sulphate and phosphate were detected by using flow-injection analysis combined with the polypyrrole-based CME electrochemical detector. All of the anions were detected conveniently and reproducibly over a linear concentration range 1-100 mug/ml. A detection limit of 0.1 mug/ml was obtained for chloride and a limit of 1.0 mug/ml for all of the other anions. Chloride, nitrate, sulphate and phosphate, following separation using ion chromatography, were detected simultaneously by using a conductivity detector and the polypyrrole-based CME electrochemical detector in series. Both methods of detection yielded similar results with comparable sensitivity, linearity and limits of detection. This method was then applied to the analysis of fresh water samples. The electrode was stable over a 2-week period of operation with no evidence of chemical or mechanical deterioration.     

224 nm Deep-UV laser for native fluorescence, a new opportunity for biomolecules detection

A new highly sensitive and compact 224 nm laser-induced native fluorescence (LINF) detector was developed using a new generation of deep-UV laser and an innovating elliptical flow cell. The use of deep-UV excitation at 224 nm allows to achieve fluorescence detection of an important range of molecules containing a single aromatic ring. The LINF detector was first evaluated in liquid chromatography. An improvement of a factor 500 over a conventional fluorimeter is reached with a limit of detection (LOD) of 1.5 pmole for ibuprofen. LODs were in the nanomole range for phenylalanine and in the picomole range for tyrosine and tryptophan. The LINF detector is able to detect the same levels of peptides concentrations as an ESI-ion trap spectrometer used in scan mode. In this application, LINF outperforms the UV detection at 214 or 254 nm and could be used with different additives with no noticeable effect on the detection.     

Analytical investigation of energy spectrums of beta rays emitted from <Superscript>90</Superscript>Sr and <Superscript>204</Superscript>Tl radioisotopes

The energy spectra of beta rays emitted from ⁹⁰Sr and ²⁰⁴Tl radioisotopes were obtained by using a silicon surface barrier detector with a 1000 μm depleted layer and 50 mm² effective area. The detector response function is interpreted by making use of range distributions of mono-energetic electrons in matter and by assuming a linear energy loss along the range in the depleted layer of the detector. An analytical expression is given for pulse height distribution obtained in the surface barrier detector. A good agreement is observed between the experimental results and theoretical interpretation.     

Chromatography of Suspensions. An Absolute Particle Size Detector Based on Turbidity-Spectra Analysis

Abstract

Herein is reported the theoretical basis for an absolute particle size detector based on turbidity-spectra analysis for the chromatography of spherical suspensions in the submicron range. A suitable detector for this purpose would be a variable wavelength spectrophotometer with very rapid scan in the wavelength range, 200–900 nm. It is proposed that such a detector be used with a liquid chromatograph which separates a spherical particle suspension according to size. An absolute detector of this kind would, to a large extent, overcome limitations of the chromatographic technique such as relatively poor resolution, flow rate variations and the lack of a particle diameter-retention volume calibration curve.     

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.     

用于天文成像探测的IRFPA性能参数测试

天体的红外成像探测在天文学领域中有其特殊和重要的作用,高性能红外探测器是红外天文观测的关键器件,因此红外焦平面阵列探测器性能参数的测试评价对于红外天文观测具有非常重要的意义。针对天文应用的特殊性,通过分析红外焦平面阵列(Infrared focal plane array,IRFPA)探测器的特点,给出了增益、读出噪声、线性和暗流等性能参数的测试原理和方法,建立了测试平台,该测试平台可实现1~14μm波长范围的IRFPA探测器性能参数测试;完成了一台采用国产3~5μm HgCdTe芯片研制的IRFPA探测器性能参数的测试。测试结果表明,该IRFPA探测器的线性度非常好,可以达到99.9%以上,但读出噪声和暗电流较大,与国外为天文观测研制的高性能探测器相比尚有很大的差距。     

Novel integrated paired emitter-detector diode (PEDD) as a miniaturized photometric detector in HPLC

A novel low power, low cost, highly sensitive, miniaturized light emitting diode (LED) based flow detector has been used as optical detector for the detection of sample components in high performance liquid chromatography (HPLC). This colorimetric detector employs two LEDs, one operating in normal mode as a light source and the other is reverse biased to work as a light detector. Instead of measuring the photocurrent directly, a simple timer circuit is used to measure the time taken for the photocurrent generated by the emitter LED (lambda(max) 500 nm) to discharge the detector LED (lambda(max) 621 nm) from 5 V (logic 1) to 1.7 V (logic 0) to give digital output directly without using an A/D converter. Employing a post-column reagent method, a Nucleosil 100-7 column (functionalized with iminodiacetic acid (IDA) groups) was used to separate a mixture of transition metal complexes, manganese(II) and cobalt(II) in 4-(2-pyridylazo)-resorcinol (PAR). All optical measurements were taken by using both the in-built HPLC variable wavelength detector and the proposed paired-emitter-detector-diode (PEDD) optical detector configured in-line for data comparison. The concentration range investigated using the PEDD was found to give a linear response to the Mn(II) and Co(II) PAR complexes. The effects of flow rate and emitter LED light source intensity were investigated. Under optimised conditions the PEDD detector offered a linear range of 0.9-100 microM and LOD of 0.09 microM for Mn-PAR complex. A linear range of 0.2-100 microM and LOD of 0.09 microM for Co-PAR complex was achieved.     

A new approach to the simultaneous multi-detection technique with electron capture and flame ionization in series

In order to avoid splitting at the column outlet for simultaneous multidetection, a new line of detector heads with the ionization cells coupled in series has been developed. The electron capture plus flame ionization detector (EC+FI-D) has been evaluated from the point of view of the sensitivity, the linear dynamic range and separation efficiency in a capillary column GC system. The performances of each section are the same as when a single ionization detector head is used.     

Comparison between a differential amperometric detector in the reductive mode and a u.v. detector in high-performance liquid chromatography with vitamin K3 as test compound

The amperometric detector is superior to the u.v. detector in terms of the limit of detection (less than 0.5 ng) and true linearity of response when vitamin K3 (menadione) is used as the test compound with a reversed-phase column. However, the high uncompensated resistance between the reference and working electrodes caused by the low conductivity of the mobile phase, restricts the upper limit of the linear range of the differential amperometric detector to about 200 ng of menadione.     

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.     

Mathematical efficiency calibration methods for high quality laboratory based gamma spectrometry systems

The efficiency calibration of laboratory based gamma spectrometry systems typically involves the purchase or construction of calibration samples that are supposed to represent the geometries of the unknown samples to be measured. For complete and correct calibrations, these sample containers must span the operational range of the system, which at times can include difficult configurations of size, density, matrix, and source distribution. The efficiency calibration of a system is dependent not only on the detector, but on the radiation attenuation factors in the detector–source configuration, and therefore is invalid unless all parameters of the sample assay condition are identical to the calibration condition. An alternative to source-based calibrations is to mathematically model the efficiency response of a given detector–sample configuration. In this approach, the measurement system is calibrated using physically accurate models whose parameters can generally be easily measured. Using modeled efficiencies, systems can be quickly adapted to changing sample containers and detector configurations. This paper explores the advantages of using mathematically computed efficiencies in place of traditional source-based measured efficiencies for laboratory samples, focusing specifically on the possibility of sample optimization for a given detector, uncertainty estimation, and cascade summing corrections.     

MALDI imaging and profiling MS of higher mass proteins from tissue

MALDI imaging and profiling mass spectrometry of proteins typically leads to the detection of a large number of peptides and small proteins but is much less successful for larger proteins: most ion signals correspond to proteins of m/z < 25,000. This is a severe limitation as many proteins, including cytokines, growth factors, enzymes, and receptors have molecular weights exceeding 25 kDa. The detector technology typically used for protein imaging, a microchannel plate, is not well suited to the detection of high m/z ions and is prone to detector saturation when analyzing complex mixtures. Here we report increased sensitivity for higher mass proteins by using the CovalX high mass HM1 detector (Zurich, Switzerland), which has been specifically designed for the detection of high mass ions and which is much less prone to detector saturation. The results demonstrate that a range of different sample preparation strategies enable higher mass proteins to be analyzed if the detector technology maintains high detection efficiency throughout the mass range. The detector enables proteins up to 70 kDa to be imaged, and proteins up to 110 kDa to be detected, directly from tissue, and indicates new directions by which the mass range amenable to MALDI imaging MS and MALDI profiling MS may be extended.