Instrument manufacturers

Particularly in the point-sensing category, many companies offer the same instrument under different private labels. In order to avoid duplication, the original manufacturer or prime distributor will be listed whenever possible. 

The charts in Appendix A provide a tabulation of all instruments known to the author on which descriptive literature was available at the time of preparation of this text. The performance characteristics are summarized rather than presented in detail. For detailed performance information, the listed manufacturer should be contacted. Appendix B is a listing of current websites, addresses and phone numbers of equipment manufacturers listed in Appendix A. The following discussions will highlight the applications for which each instrument category and group is particularly suited based on configuration or performance eharacteristics. Appliea-tions themselves are discussed in detail in Chapters 6 through 12. 

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The instrument manufacturer recommended four independent instruments and this solution was finally chosen. 

On the other hand, the NDT service business has evolved towards a more open market, in which the prime contractor requires a transparent access to the data provided by the supplier, in order to ensure the comparison of data obtained from different sources and at different periods of time. Existing fomiats are most of the time proprietary formats released by instrument manufacturers, generally dealing with a unique NDT method and not including complementary information on the acquisition consequently, they fail to meet these requirements. 

Finally, we note that the size and shape of the particles of the packing, the packing technique, and column dimensions and configuration are additional factors which influence a GPC experiment. In addition, the flow rate, the sample size, the sample concentration, the solvent, and the temperature must all be optimized. Details concerning these considerations are found in analytical chemistry references, as well as in the technical literature of instrument manufacturers. 

Professional scientific controlling instruments Manufacture of engineering, laboratory, and research instruments and associated equipment Metals, plastics, resins, glass, wood, rubber, fibers, abrasives... 

This on-going research aims at a) environmental monitoring and b) the development, after further research and collaboration with an instrument manufacturer, of a prototype portable flow toxicity meter as an early warning system for pollution. 

Chans such as this, but in more detail, are provided by all the XPS instrument manufacturers. They are based on extensive collections of data, much of which comes from Reference 1. 

Unfortunately, some of the data that are required to calculate the specifications and operating conditions of the optimum column involve instrument specifications which are often not available from the instrument manufacturer. In particular, the total dispersion of the detector and its internal connecting tubes is rarely given. In a similar manner, a value for the dispersion that takes place in a sample valve is rarely provided by the manufactures. The valve, as discussed in a previous chapter, can make a significant contribution to the extra-column dispersion of the chromatographic system, which, as has also been shown, will determine the magnitude of the column radius. Sadly, it is often left to the analyst to experimentally determine these data. 

For calibration of the 0 to 100% LEL scale, test kits containing known concentrations of combustible gases (usually either 2.5% methane or 2.5% natural gas) are available from the instrument manufacturers. In using these kits, it should be borne in mind that the calibration is only for that sjiecific gas and indicates only that the meter is operational on the 0 to 100% LEL scale. To calibrate to 0 to 10% scale, it is necessary to use purchased or specifically prepared known concentrations of gases in the TLV ranges. 

Usually there is no opportunity to repeat the measurements to determine the experimental variance or standard deviation. This is the most common situation encountered in field measurements. Each measurement is carried out only once due to restricted resources, and because field-measured quantities are often unstable, repetition to determine the spread is not justified. In such cases prior knowledge gained in a laboratory with the same or a similar meter and measurement approach could be used. The second alternative is to rely on the specifications given by the instrument manufacturer, although instrumenr manufacturers do not normally specify the risk level related to the confidence limits they are giving. 

The time constant is one way of determining the dynamic features of a measurement system. Not all instrument manufacturers use the time constant some use the response time instead. The response time is the time between a step change of the measured quantity and the instant when the instrument s response does not differ from its final value by more than a specified amount.The response time is defined according to a deviation from the final value. Often response times for the relative deviation of 1%, 5%, 10%, or 37% are used. The corresponding response times are denoted by 99%, 95%, 90%, or 63% response time, respectively. The response time for a first-order system can be solved from Eq. (12.15). Note that the 63% response time of a first-order system is the same as the time constant r of the system. 

These last three are special valves from the viewpoint of chemical and petrochemical plant applications, but they can be designed by the major manufacturers and instrumentation manufacturers as these are associated with instrumentation controls. Care must be taken in the system design to make certain it meets all ASME code requirements. 

This section is concerned with describing the equipment which is necessary for an introduction to spectrographic techniques for the analyst. In this instance the practical work will be described for instruments manufactured by Rank Hilger, Margate, Kent, UK, but the comparable products of other manufacturers may also be used. 

Double-beam AA spectrophotometers are still marketed by instrument manufacturers. A double-beam system compensates for changes in lamp intensity and may require less frequent re-zeroing than a single-beam instrument. These considerations had more merit some years ago when hollow cathode lamps suffered from some instability. It should be noted, however, that the optical... 

The data presented in Table 21.4, in conjunction with the experimental details given in Sections 21.21-21.26, will enable the determination of most elements to be carried out successfully. For detailed accounts of the determination of individual elements by atomic absorption spectroscopy, the Bibliography (Section 21.27) should be consulted. In addition, most instrument manufacturers supply applications handbooks relative to the apparatus in which full experimental details are given. 

Procedure. Follow the conditions recommended by the instrument manufacturers for the determination of arsenic by hydride generation. Typical instrumental... 

The idea of using CPCM for shielding is rather alluring. Indeed, a casing of an article or instrument manufactured of such a material serves at the same time as a screen to protect against electromagnetic radiation. All the above-described operations involved in applying additional layers become unnecessary. 

In the positive ion mode, calibration is most frequently performed using perfluorokerosine, but different instrument manufacturers recommend different reference materials. Consult your instrument manual for the recorn-... 

Limitations. Most commercial cytometers require 5-60 s to pressurize the cell sample and deliver it to the point of analysis. We developed a special sample chamber which delivers sample in three seconds in some machines (25). The fact that commercially available software has only recently been written and the reluctance of instrument manufacturers to make available source code has probably delayed by a few years the widespread application of this technology. 

Particle Size Laser Refractometiy is based upon Mie scattering of particles in a liquid medium. Up until about 1985, the power of computers supplied with laser diffraction instruments was not sufficient to utilize the rigorous solution for homogeneous spherical particles formulated by Gustave Mie in 1908. Laser particle instrument manufacturers therefore used approximations conceived by Fraunhofer. 

What if instrument manufacturers would adopt specific RMs Until now, there has been a general tendency for instrument manufacturers to avoid admitting the need for RMs. If instrument manufacturers could be convinced to make a serious appraisal of needs in the field, they might provide some resources to help meet those needs (Rasberry 1998). After all, the extra cost of providing suitable RMs, as a part of an annual service contract costing US 20 000 on an instmment that is worth US 2 million is quite insignificant. 

Implementation of SFC has initially been hampered by instrumental problems, such as back-pressure regulation, need for syringe pumps, consistent flow-rates, pressure and density gradient control, modifier gradient elution, small volume injection (nL), poor reproducibility of injection, and miniaturised detection. These difficulties, which limited sensitivity, precision or reproducibility in industrial applications, were eventually overcome. Because instrumentation for SFC is quite complex and expensive, the technique is still not widely accepted. At the present time few SFC instrument manufacturers are active. Berger and Wilson [239] have described packed SFC instrumentation equipped with FID, UV/VIS and NPD, which can also be employed for open-tubular SFC in a pressure-control mode. Column technology has been largely borrowed from GC (for the open-tubular format) or from HPLC (for the packed format). Open-tubular coated capillaries (50-100 irn i.d.), packed capillaries (100-500 p,m i.d.), and packed columns (1 -4.6 mm i.d.) have been used for SFC (Table 4.27). 

In fact continuous titration belongs to this class, but has already been treated above on the basis of the use of the sensor merely as an end-point indicator of the titration reaction. For the remaining non-separational flow techniques, such a multiplicity of concomitant developments has occured since 1960 that in a survey we must confine ourselves to a more or less personal view based substantially on the information obtained from some important reviews and more specific papers presented at a few recent conferences78 82, or from leaflets offered by commercial instrument manufacturers. The developments are summarized in Table 5.1. 

The sample is introduced into the spectrometer, locked onto the deuter-ated solvent (here CDC13) and the homogeneity optimized by shimming as described by the instrument manufacturer (this can often be done automatically, particularly when a sample changer is used). 

Most of the hplc instrumentation now in use is unsuitable for small bore columns. At the moment, the technique is used mainly in the applications laboratories of some instrument manufacturers (they are interested in selling it ). The method is potentially attractive in areas where sample sizes are very limited, for example in biochemical or life sciences applications, but whether or not it becomes widely accepted remains to be seen. 

Column inlet pressures in hplc can be as much as 200 times atmospheric pressure, and hplc columns are packed using much larger pressures (up to 700 times atmospheric). The SI unit of pressure is the Pascal (1 Pa = 1 Nm-2) normal atmospheric pressure is about 105 Pa. Because it is convenient to express pressure using reasonably small numbers, experimental workers and instrument manufacturers report pressures in bar, or pounds per square inch (psi), or sometimes in kg cm-2. The bar is defined by 1 bar = 105 Pa, so that 1 bar corresponds roughly to normal atmospheric pressure. You will need to be able to convert between these units. 

From this equation it can be seen that the depth of penetration depends on the angle of incidence of the infrared radiation, the refractive indices of the ATR element and the sample, and the wavelength of the radiation. As a consequence of lower penetration at higher wavenumber (shorter wavelength), bands are relatively weaker compared to a transmission spectrum, but surface specificity is higher. It has to be kept in mind that the refractive index of a medium may change in the vicinity of an absorption band. This is especially the case for strong bands for which this variation (anomalous dispersion) can distort the band shape and shift the peak maxima, but mathematical models can be applied that correct for this effect, and these are made available as software commands by some instrument manufacturers. 

Furthermore, true fundamental understanding could also be applied in reverse. Then instrument manufacturers could concentrate on those aspects of construction and operation that affect the transferability situation, and be able to verify their capabilities in an unambiguous, scientifically valid and agreed-on manner. 

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