Instrumentation ideal properties

Biosensors with their oft-quoted (ideal) properties would seem to be ready partners for industrial analysts who want information at point-of-need, but as has been pointed out many times, few examples have had the same success as the blood glucose sensors for use in the home (albeit this is an example from medicine rather than industry). The reasons for this have also been pointed out many times, the principal one being that the development and manufacture of the blood glucose sensors is supported by the sadly huge market for diabetic testing and the large amount of investment capital which accrues to that market [6,7]. Further, blood is a sample of reasonably constant composition (in this context), the information is truly useful to the client and the desire for information at home means there is less competition from laboratory-based instruments. This is in contrast to the diverse requirements for analysis in the food industry (for example) which make up a series of... 

Instrument response can be calibrated by the addition of an internal standard, which will minimize variability in both ionization processes and sample preparation. The ideal properties of the internal standard, as well as additional requirements for analytical methods, are discussed in Chapter 6. 

A further important property of the two instruments concerns the nature of any ion sources used with them. Magnetic-sector instruments work best with a continuous ion beam produced with an electron ionization or chemical ionization source. Sources that produce pulses of ions, such as with laser desorption or radioactive (Californium) sources, are not compatible with the need for a continuous beam. However, these pulsed sources are ideal for the TOF analyzer because, in such a system, ions of all m/z values must begin their flight to the ion detector at the same instant in... 

Austenitic steels have a number of advantages over their ferritic cousins. They are tougher and more ductile. They can be formed more easily by stretching or deep drawing. Because diffusion is slower in f.c.c. iron than in b.c.c. iron, they have better creep properties. And they are non-magnetic, which makes them ideal for instruments like electron microscopes and mass spectrometers. But one drawback is that austenitic steels work harden very rapidly, which makes them rather difficult to machine. 

Many techniques ideally suited for nanostructure characterization unfortunately depend also on the substrate properties. For example, the reflectivity and conductivity of a substrate play an important role in the successful execution of the instrumental method. Hence, substrate-independent techniques are needed so that structure and/or behavior of the material can be investigated in a confined geometry, decoupled from the potentially invasive effect of the substrate-mate-rial interface. 

Ideally, measuring radioactivity in water assets in the field would involve minimal sampling and sample preparation. However, the physical properties of specific types of radiation combined with the physical properties of water make evaluating radioactivity in water assets in the field somewhat difficult. For example, alpha particles can only travel short distances and they cannot penetrate through most physical objects. Therefore, instruments designed to evaluate alpha emissions must... 

The qualitative analysis of retention behaviour in liquid chromatography has now become possible. Quantitative retention-prediction is, however, still difficult the prediction of retention time and the optimization of separation conditions based on physicochemical properties have not yet been completely successful. One reason is the lack of an ideal stationary phase material. The stationary phase material has to be stable as part of an instrument, and this is very difficult to achieve in normal-phase liquid chromatography because the moisture in organic solvents ages the silica gel. 

Only a few physicochemical parameters can be measured by immersing the relevant instrument into a water body. In most cases a small fraction of a given water population or sample is collected and analyzed. The aim of taking samples or sampling is to extract a fraction of the water body that has chemical, physical, and biological properties identical to those of the bulk of the system to be studied. Ideally, all the characteristics of the sample, or at least, the parameters that are to be determined, should not change until the time of measurement. Only then can the results of the sample analysis be representative of the composition of the system under scrutiny. 

If one focuses on the particle size distribution function as a central framework for describing aerosols, one can conveniently classify the measurement instruments according to the properties of the size distribution function. Organization of instrumentation gives perspective on the ideal requirements as contrasted with the practical limits imposed by current technology. An idealized hierarchy was suggested by S. K. Friedlander in 1977. As an ideal, the modern aerosol analyzer gives a continuous... 

The ideal internal standard is the same element as the analyte because it has similar mass, ionization energy, and chemical properties. Therefore, isotope dilution based calibration provides high accuracy as long as isotope equilibration is attained and the measured isotopes are free of spectral overlaps [192,193]. Standards do not need to be matrix-matched. Quadrupole-based ICP-MS instruments can typically provide isotope ratio precision of 0.1% to 0.5%. Much better isotope ratio precision can be obtained by using simultaneous MS detection, such as a multicollector-based instrument or perhaps time-of-flight MS. In comparison to thermal ionization mass spectrometry, ICP-MS provides much higher sample throughput and simpler, faster sample preparation. 

Though not instrumental in nature, another important technique in the polymer arsenal is large-scale computer simulation experiments. These have proved especially useful over the last several years in, for example, molecular-level simulations of polymer mechanical properties [42] and of the transport properties of concentrated polymer solutions [43], Polymers are in many ways ideal objects for this level of simulation study although it is difficult to have accurate detailed knowledge of local interactions, as mentioned earlier, much polymer behavior is dominated by nonlocal interactions that can be much more adequately represented. 

---