Detector various

There are two principal neutron imaging techniques in NR - direct and transfer (indirect). In the former the neutron converter and the detector are simultaneously exposed in the neutron beam while in the transfer technique only the converter screen is exposed and activated by the neutrons, and transfered out of the neutron beam to subsequently expose the detector. Various types of IP can be used in both of neutron imaging techniques. 

Lawrence et al. described a simpler post-column ion-pair derivatization technique, whereby the alkaloids were separated by means of an organic mobile phase on silica gel. The column eluate and the aqueous DAS solution were mixed and the two immiscible phases separated. About 50% of the organic phase was led to the fluorimetric detector. Various parameters influencing the bandwidth were investigated, i.a. the influence of methanol in the mobile phase. An increasing methanol content deteriorated the signal to noise ratio, and the most useful range was 0-15% methanol. The detection limit for atropine was found to be 40 ng. 

A variety of analytical methods has been used for determining trace concentrations of PAHs in environmental samples (Table 6-2). These include GC with various detectors, HPLC with various detectors, and TLC with fluorimetric detectors. Various detection devices used for GC quantification include FID, MS, Fourier transform infrared spectrometer (FT-IR), laser induced molecular fluorescence detector (LIMF), diode array detector (DAD), and gas phase fluorescence detector (GPFDA). GC/MS and HPLC with UV or spectrofluorimetric detectors are perhaps the most prevalent analytical methods for determining concentrations of PAHs in environmental samples. 

Photomultiplier tubes (PMTs) are the most commonly used detectors, various types are available for different applications. In general they are sensitive in the range from 200 to 600 nm, with maximum sensitivity obtained in the 300—500 nm range. Red-sensitive PMTs are also available for investigations beyond 600 nm. The PMT housings are sometimes cooled to temperatures as low as —40 °C to minimize temperature-dependent noise. 

As an alternative to universal calibration, one can measure the molecular weight of the eluting species on-line using a detector that responds continuously to the size of the solute. The two most common detectors used for this purpose are the LALLS detector and the CV detector. Various designs of both detectors have been reported (8-14). It should be noted first that these detectors obviate the necessity for universal calibration to translate the SEC retention time into molecular weight, but they do not remove problems that may exist with regard to the response of the concentration detector, which, as mentioned, is usually a DRI or an infrared instrument. 

Detectors Various detectors can be used in combination with GC for the determination of mercury species. An ECD is a sensitive detector with an absolute detection limit of a few picograms. It does not, however, measure mercury directly, but responds to the halide ion attached to the CH3Hg ion. The identification of small methylmercury peaks can sometimes be subject to a positive systematic error owing to coeluting contaminants. The use of a plasma atomic emission detector, a mass spectromet-ric detector, CV-AAS, CV-AFS, or ICP-MS can avoid such problems, since mercury is measured directly. 

The chromatogram can finally be used as the series of bands or zones of components or the components can be eluted successively and then detected by various means (e.g. thermal conductivity, flame ionization, electron capture detectors, or the bands can be examined chemically). If the detection is non-destructive, preparative scale chromatography can separate measurable and useful quantities of components. The final detection stage can be coupled to a mass spectrometer (GCMS) and to a computer for final identification. 

Among the various detectors specific for nitrogen, the NPD (Nitrogen Phosphorus Thermionic Detector) we will consider, is based on the following concept the eluted components enter a conventional FID burner whose air and hydrogen flows are controlled to eliminate the response for hydrocarbons. 

Various computed tomography CT- scanners for industrial applications have been designed and constructed) They use as radiation sources X-ray tubes or gamma emitting radioisotopes and as detectors NaI(Tl)-scintillators for gamma rays and image intensifiers for X-rays. 

New technological capabilities in the performance of ultrasonic testing were implemented in the application of computerised flaw detectors, which allow development of new technologies and control of various especially critical and complex components. 

The Institute has many-year experience of investigations and developments in the field of NDT. These are, mainly, developments which allowed creation of a series of eddy current flaw detectors for various applications. The Institute has traditionally studied the physico-mechanical properties of materials, their stressed-strained state, fracture mechanics and developed on this basis the procedures and instruments which measure the properties and predict the behaviour of materials. Quite important are also developments of technologies and equipment for control of thickness and adhesion of thin protective coatings on various bases, corrosion control of underground pipelines by indirect method, acoustic emission control of hydrogen and corrosion cracking in structural materials, etc. 

The ions in a beam that has been dispersed in space according to their various m/z values can be collected simultaneously by a planar assembly of small electron multipliers. All ions within a specified mass range are detected at the same time, giving the array detector an advantage for analysis of very small quantities of any one substance or where ions are produced intermittently during short time intervals. 

Confirmation of the identities of nitrosamines generally is accompHshed by gas chromatography—mass spectrometry (gc/ms) (46,87). High resolution gc/ms, as well as gc/ms in various single-ion modes, can be used as specific detectors, especially when screening for particular nitrosamines (87) (see Analytical LffiTHODS Trace and residue analysis). 

CCD. Although front-side iEuminated devices are available, the MPP CCD is typically back-side ikuminated in order to achieve state-of-the-art photon collection performance. Even with this stipulation the MPP CCD is still a popular detector due to its availabiUty in various array sizes and formats specifically designed for scientific appHcations. 

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