General instrumentation

Instrumentation for electrochemical experiments has undergone rapid development, allowing much greater precision and accuracy in control 

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Finally, probably the most important item affecting an ion beam is the overall gas pressure inside the instrument. Generally, a mass spectrometer operates under a high vacuum, in which... 

Spectrophotometry. The instrument generally used for this basic type of measurement is the spectrophotometer. The data obtained, usually pictured in the form of a spectrophotometric curve, indicate the ability of the sample to transmit or reflect light of the various wave lengths. Various instruments are available which can be used to determine more or less complete spectrophotometric curves. 

Despite shortcomings, the Micromerograph in the early 1960 s was the only instrument generally available for determining particle size distribution of sub-sieve pro pint and pyrotechnic ingredients. 

The instruments generally yield very precise measurements (E, CV ... 

There are many other examples in the literature where sealed-vessel microwave conditions have been employed to heat water as a reaction solvent well above its boiling point. Examples include transition metal catalyzed transformations such as Suzuki [43], Heck [44], Sonogashira [45], and Stille [46] cross-coupling reactions, in addition to cyanation reactions [47], phenylations [48], heterocycle formation [49], and even solid-phase organic syntheses [50] (see Chapters 6 and 7 for details). In many of these studies, reaction temperatures lower than those normally considered near-critical (Table 4.2) have been employed (100-150 °C). This is due in part to the fact that with single-mode microwave reactors (see Section 3.5) 200-220 °C is the current limit to which water can be safely heated under pressure since these instruments generally have a 20 bar pressure limit. For generating truly near-critical conditions around 280 °C, special microwave reactors able to withstand pressures of up to 80 bar have to be utilized (see Section 3.4.4). 

An instrument, generally in the form of a liquid-filled U-tube, for measuring pressures of gases. Masterbatch... 

Flame emission spectrometry is used extensively for the determination of trace metals in solution and in particular the alkali and alkaline earth metals. The most notable applications are the determinations of Na, K, Ca and Mg in body fluids and other biological samples for clinical diagnosis. Simple filter instruments generally provide adequate resolution for this type of analysis. The same elements, together with B, Fe, Cu and Mn, are important constituents of soils and fertilizers and the technique is therefore also useful for the analysis of agricultural materials. Although many other trace metals can be determined in a variety of matrices, there has been a preference for the use of atomic absorption spectrometry because variations in flame temperature are much less critical and spectral interference is negligible. Detection limits for flame emission techniques are comparable to those for atomic absorption, i.e. from < 0.01 to 10 ppm (Table 8.6). Flame emission spectrometry complements atomic absorption spectrometry because it operates most effectively for elements which are easily ionized, whilst atomic absorption methods demand a minimum of ionization (Table 8.7). 

Authors must also describe the instrumentation or scientific apparatus that they used in their work. (Note that ordinary equipment, e.g., a distillation apparatus or a rotary evaporator, should not be described.) Instrumentation generally falls into two categories custom-built or commercial. Custom-built instrumentation... 

To successfully measure non-Newtonian fluids, a known shear field (preferably constant) must be generated in the instrument. Generally, this situation is known as steady simple shear. This precludes the use of most single-point viscometers and leaves only rotational and capillary devices. Of these, rotational devices are most commonly used. To meet the criterion of steady simple shear, cone and plate, parallel plates, or concentric cylinders are used (Figure HI. 1.1). 

The size of the fixture is chosen based on the testing material and the sensitivity of the instrument. (Usually, various sizes and types of fixtures are available for an instrument.) Generally, responding torque becomes larger as the diameter of the fixture is increased or as the gap between the fixture surfaces decreases. 

A mid-infrared absorption instrument generally consists of a Fourier transform design with the same basic components as noted above for the Fourier transform near-infrared spectrometers (broadband light source, Michelson interferometer, and detector optimized for the mid-infrared spectral region.)... 

When the imposed light beam interacts with the sample, its response must then be detected by the instrument. Generally, for a given detector, when the incident light source is shorter in wavelength, the instrument is more sensitive to smaller particles. A combination of transmitted, forward-scatter and back-scatter detectors and black mirrors increase the accuracy and stability of the instrument and decrease the stray light (for instance in Instruments A and F). The source/de-tector combination defines the effective spectral characteristics of the instrument and the manner in which it responds to a sample. 

Multi-component hydrocarbon standards to provide accurate calibration of instruments (generally gas chromatographs) used to monitor the concentrations of a wide range of volatile organic hydrocarbon compounds (VOCs) in ambient air. These standards currently contain 30 different hydrocarbon species that are important to photochemical ozone formation, with concentrations ranging down to a few parts per billion by molar value. They are disseminated widely in the United Kingdom and the rest of Europe as calibration standards, and as test mixtures for assessment of the quality of international ambient hydrocarbon measurements (often under the auspices of the European Commission - EC). 

There is an exaggerated tendency among many technicians making dust surveys toward a simple dust-counting instrument. Generally, it is desired to make daily or weekly inspections, but the actual need is for a rapid method of making dust counts. While it is admittedly useful to have an instrument both rapid and reliable, it must be stressed that frequent dust surveys are not necessary. The pneumoconioses develop only after many years of exposure to dust. Consequently, only two, or at most three, annual surveys are necessary to evaluate exposure in any dusty trade. Control equipment, once tested to assure effective removal of dust, will continue to perform so long as it is maintained in... 

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