High resolution systems

X-ray topographic systems are simply high resolntion diffractometers in which the beam is made large enough to cover the area of crystal reqtrired, or in which 

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GC-FTIR, GC-AED, GC-ICP-MS, cf. Chapter 7), fast GC separations (1996) and most recently the development of sophisticated injectors with temperatureprogramming capability and high-resolution systems (GC-ToFMS). As a result, modem GC systems are quite advanced (Scheme 4.3) and GC is one of the most widely applied instrumental techniques. 

ICP-MS (inductively coupled plasma mass spectrometry) is frequently used for determining ultratrace amounts of technetium [9]. In spite of the high cost of the equipment, this detection method is far superior to other radiometric methods as regards sensitivity. When a double focussing high-resolution system is used (HR-ICP-MS) and an ultrasonic nebulizer is introduced [10], the detection limit is in the order 0.002 mBq. The ICP-MS method has been successfully applied to the determination of environmental "Tc as well as to other long-lived radionuclides of neptunium and plutonium in the environment. 

Brominated and chlorinated organic flame-retardants can be analysed using either GC-MS or LC-MS. High resolution systems are required to identify the specific isomers. Quantification by bromine or chlorine content is normally achieved using XRF against standards in the same matrix. 

Modern GC instruments represent high resolution systems that are fully automated from sample injection to final data reduction. Utilization of new injection devices has provided the means to enhance the performance level significantly. Studies have shown, for example, that injection of the tranquilizer propio-nylpromazine and its sulfoxide into a hot injection port gave much poorer results than on-column injection at low temperature (44). In the latter case, however, nonvolatile sample components could enter the column. This disadvantage of classic sample injection can be eliminated through use of a programmed temperature vaporization (PTV) injector. 

Many other useful results have been found with high-resolution systems, and many of these have been reported in the previously mentioned symposia series (S4, S6, S8). 

Finally, it is apparent that the field of medicine is moving toward the acceptance of and active pursuance of preventive medicine. The use of multiphasic screening laboratories is becoming more widespread to achieve this end. In such programs, the aim is to detect incipient diseases so they can be treated prior to the need for expensive hospitalization. So far, many of the tests and techniques used in these facilities have been adapted from the clinical laboratory that operates in the hospital where acutely sick patients are present. It is obvious that as we gain more knowledge of the chemical indicators of disease, tests that are more definitive for these indicators must be developed. High-resolution systems seem uniquely suitable to such a task as they become truly economic systems. 

Laboratory systems equipped with movements accurate to the ten-thousandth of a degree and that use parallel geometry can achieve an uncertainty in the range of 10 ppm. Very high resolution systems associated with synchrotron sources can achieve an uncertainty close to 1 ppm [HAR 90], We have to point out, however, that the tests conducted on a same sample by several laboratories generally lead to much greater errors. The differences between the measured values are often in the range of 100 ppm [PAR 60, MAS 96b]. 

Figure 4.8. Rietveldfitting of an X-ray diffraction pattern obtained with a sample of cerium oxide. This pattern was produced by using a high resolution system with a synchrotron radiation source at the ESRF, with a wavelength equal to 0.39982 A [BAL 04]...

Very high resolution systems (voxel diameters of 1 mm or less) may replace exploratory procedures such as endoscopy. The scan data can be processed interactively to give the physician views corresponding to a virtual endoscopic examination under his control. However, parallel studies in which hundreds of patients receive literal or virtual visualization procedures with comparison of diagnostic accuracy, and long term outcome will be necessary before virtual examinations can be accepted as the standard of medical care, see also Nuclear Magnetic Resonance Spectroscopy. 

In a high resolution system this can be significant, on the order of 10 to 10. In the infrared region the noise is generally independent of signal strength so the advantage holds. 

HARRIS-2 employs high-resolution systems for the measurement of road shape and visual condition. Pavement shape measurements are provided by a scanning laser measurement system that offers unparalleled capability for measurement of transverse unevenness, such as rutting and longitudinal deformation. HARRIS-2 also provides a state-of-the-art image collection system that provides high-speed/high-resolution linescan cameras in conjunction... 

Spectrometer lengths are typically 300 mm for medium resolution or 800 mm for high resolution systems. The dispersion per pixel is thus typically 1 cm for a 300 mm length spectrometer with an 1800 mm grating operating at 633 nm and can be as low as 0.25 cm for a high resolution system. The resolution of... 

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