Basic Instrumentation Considerations

In addition to the specialist mixing equipment described later in this section, the following common instruments are extremely useful for a variety of tasks in the mixing laboratory  

Handheld optical tachometer used to calibrate and check the digital speed 

Digital (or other high-quality) video camera (and tripod) to record visualization experiments. 

Distilled or deionized water supply to provide clean water of repeatable quality and low conductivity. 

Electronic balance accurate to 0.001 g for weighing of tracer materials, indicator solutions, density measurements, etc. 

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The basic instrumentation for capillary electrophoresis is shown in Figure 12.41 and includes a power supply for applying the electric field, anode and cathode compartments containing reservoirs of the buffer solution, a sample vial containing the sample, the capillary tube, and a detector. Each part of the instrument receives further consideration in this section. 

NFPA 69 (NFPA 1997) contains information on basic design considerations, design and operating requirements, and instrumentation requirements. Appendix D presents methods for ventilation calculations, including the time required for ventilation to reduce the concentration to a safe limit, the number of air changes required for reaching a desired... 

The short (UV) wavelength limit of the optical range is imposed by instrumental considerations (spectrophotometers do not usually work at wavelengths shorter than about 200 nm) and by the validity of the macroscopic Maxwell equations. These equations assume a continuous medium in other words, that there is a large number of ions within a volume of. The long (IR) wavelength limit of the optical range is basically imposed by experimental considerations (spectrophotometers work up to about 3000 nm). 

Cost Effectiveness. As with the other advantages of immunochemical analysis, cost may be quite variable. Reagent costs for several automated systems have been estimated at under 1.25 per sample. The cost is obviously much lower for less sophisticated assay systems, especially if some reagents are prepared in house. A major consideration is the expense of new instrumentation. For dedicated or automated instrumentation for either RIA or ELISA procedures, the cost may be 50-100,000. However, most analytical laboratories already have the basic instrumentation needed for immunoassays. Moderate sensitivity can be obtained through the use of numerous procedures such as radial immunodiffusion and hemagglutination. These procedures require no expensive equipment or reagents and they may be very useful in areas where equipment acquisition or maintenance is a problem. 

To use the technique optimally, it is essential to have a sound grasp of both the principles underlying the methods and the most appropriate measurement parameters to be used for each sample. This chapter deals with the former consideration in that the basic instrument operation and the principles underlying the measurement process will be described, whereas Chapter 2 outlines the basic issues associated with the choice of experimental parameters and calibration. Chapter 3 then goes on to describe some of the principal applications of DSC within the pharmaceutical field. 

Work continues on developing equations for interfacial viscosity, where both fluids are liquids, and for non-Newtonian surface behavior, where ps varies with stress. In all such cases the deep channel geometry considerably simplifies these derivations. As these analyses are developed, the promise of this arrangement as a basic instrument should improve. 

The radiation and temperature dependent mechanical properties of viscoelastic materials (modulus and loss) are of great interest throughout the plastics, polymer, and rubber from initial design to routine production. There are a number of laboratory research instruments are available to determine these properties. All these hardness tests conducted on polymeric materials involve the penetration of the sample under consideration by loaded spheres or other geometric shapes [1]. Most of these tests are to some extent arbitrary because the penetration of an indenter into viscoelastic material increases with time. For example, standard durometer test (the "Shore A") is widely used to measure the static "hardness" or resistance to indentation. However, it does not measure basic material properties, and its results depend on the specimen geometry (it is difficult to make available the identity of the initial position of the devices on cylinder or spherical surfaces while measuring) and test conditions, and some arbitrary time must be selected to compare different materials. 

Now let us consider utility failure as a cause of overpressure. Failure of the utility supphes (e.g., electric power, cooling water, steam, instrument air or instrument power, or fuel) to refinery plant facihties wiU in many instances result in emergency conditions with potential for overpressuring equipment. Although utility supply systems are designed for reliability by the appropriate selection of multiple generation and distribution systems, spare equipment, backup systems, etc., the possibility of failure still remains. Possible failure mechanisms of each utility must, therefore, be examined and evaluated to determine the associated requirements for overpressure protection. The basic rules for these considerations are as follows ... 

Any obstruction inserted into a duct or pipe that creates a measurable pressure difference can be used as a flow meter. The three basic standardized flow measurement devices presented above are perhaps more suitable for laboratory work than installation as permanent ductwork instruments in ventilation applications. They are sensitive to flow disturbances, relatively expensive, require considerable space, and have a narrow measurement range and a high permanent pressure loss. For these reasons, numerous attempts have been made to develop instruments without these drawbacks. Some of them, like the... 

However, in LC solutes are partitioned according to a more complicated balance among various attractive forces solutes interact with both mobile-phase molecules and stationary-phase molecules (or stationary-phase pendant groups), the stationary-phase interacts with mobile-phase molecules, parts of the stationary phase may interact with each other, and mobile-phase molecules interact with each other. Cavity formation in the mobile phase, overcoming the attractive forces of the mobile-phase molecules for each other, is an important consideration in LC but not in GC. Therefore, even though LC and GC share a considerable amount of basic theory, the mechanisms are very different on a molecular level. This translates into conditions that are very different on a practical level so different, in fact, that separate instruments are required in modern practice. 

Our knowledge of biological membrane ultrastructure has increased considerably over the years as a result of rapid advances in instrumentation. Although there is still controversy over the most correct biological membrane model, the concept of membrane structure presented by Davson and Danielli of a lipid bilayer is perhaps the one best accepted [12,13]. The most current version of that basic model, illustrated in Fig. 7, is referred to as the fluid mosaic model of membrane structure. This model is consistent with what we have learned about the existence of specific ion channels and receptors within and along surface membranes. 

There is no need for much fantasy to see the relation between a roof-shaped (Fig. 12) and a scissor-like basic structure (cf. Fig. 11). Nevertheless, the following point should be noted Scissor-like molecules (cf. 1) provide considerable (inherent) bulkiness merely due to the basic skeleton. On the other hand, as far as roof-shaped molecules are concerned [cf. 26 (Fig. 12) and 27-42], the presence of polar substituents, suitably positioned, preferably at the top ridge of the molecular roof, are also instrumental in developing molecular bulkiness. 

This section on protective measures discusses three elements (1) containment, (2) instrumentation and detection of a runaway, and (3) mitigation measures. For each element, examples are given to illustrate the principles discussed. This section is basically a summary of protective measures, not an exhaustive treatise. Protective measures are necessary considerations, and in fact, safety requirements, when handling reactive substances and exothermic reactions. 

One of the most basic requirements in analytical chemistry is the ability to make up solutions to the required strength, and to be able to interpret the various ways of defining concentration in solution and solids. For solution-based methods, it is vital to be able to accurately prepare known-strength solutions in order to calibrate analytical instruments. By way of background to this, we introduce some elementary chemical thermodynamics - the equilibrium constant of a reversible reaction, and the solubility and solubility product of compounds. More information, and considerably more detail, on this topic can be found in Garrels and Christ (1965), as well as many more recent geochemistry texts. We then give some worked examples to show how... 

The basic considerations for spectrophotometer maintenance are safely and cleanliness. Maintaining a safe and clean work environment ensures a longer life for the instruments and a lower likelihood for problems relating to contamination, broken or misaligned parts, or injury. Solutions spilled on sensitive electronic circuits can render them inoperative. Any spills should be cleaned up immediately according to local safety protocols. 

This basically means that two instruments have been linked together. The first analyser can replace the traditional chromatographic separation step and is used to produce ions of chosen m/z values. Each of the selected ions is then fragmented by collision with a gas, and mass analysis of these product ions effected in the second analyser. The resulting mass spectrum is used for their identification. The potential combinations of the various magnetic sector and quadrupole instruments to form such coupled systems is considerable. Ion traps may also be operated in a tandem MS mode. 

The basic ESCA instrumentation allows considerable flexibility in the design of equipment for ancillary experiments and it is possible to construct a reaction chamber such that samples may be directly passed into the source region of the spectrometer subsequent to plasma treatment and a typical design is shown in Fig. 31. Typical of the results of such an investigation are those pertaining to a largely alternating copolymer of ethylene and tetrafluoroethylene (48% 52%) treated in a... 

The Strategic Planning section deals with considerations regarding instrumentation and reagents for CD spectrometry. The Basic Protocol outlines the steps in recording a CD spectrum. The two support protocols explain the interpretation of CD spectra—Support Protocol 1 deals with near-UV spectra and Support Protocol 2 with far-UV spectra. 

This unit will introduce two fundamental protocols—the Wilhelmy plate method (see Basic Protocol 1 and Alternate Protocol 1) and the du Noiiy ring method (see Alternate Protocol 2)—that can be used to determine static interfacial tension (Dukhin et al., 1995). Since the two methods use the same experimental setup, they will be discussed together. Two advanced protocols that have the capability to determine dynamic interfacial tension—the drop volume technique (see Basic Protocol 2) and the drop shape method (see Alternate Protocol 3)—will also be presented. The basic principles of each of these techniques will be briefly outlined in the Background Information. Critical Parameters as well as Time Considerations for the different tests will be discussed. References and Internet Resources are listed to provide a more in-depth understanding of each of these techniques and allow the reader to contact commercial vendors to obtain information about costs and availability of surface science instrumentation. 

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