Centrifugation instrumentation

A recent review on CCC as a preparative tool [3] described an extremely useful comparison of four different CCC approaches and concluded that the real future belongs to the new generation of centrifugal instruments. They concluded that more reliable designs were required, that there was a need to accommodate higher loads on the 100-g to 1-kg scale, and that truly preparative instruments needed to be developed. They called for a better understanding of the mechanisms of separation in order to achieve this. 

Several sophisticated centrifugal instruments for concurrent sampling and sizing of aerosols were developed in the period from 1950 to 1980 [42—46]. These tend to have been displaced by laser diffraction studies (see Chapter 7) and time-of-flight aerosol... 

The two principal elements of evaporator control are evaporation rate a.ndproduct concentration. Evaporation rate in single- and multiple-effect evaporators is usually achieved by steam-flow control. Conventional-control instrumentation is used (see Sec. 22), with the added precaution that pressure drop across meter and control valve, which reduces temperature difference available for heat transfer, not be excessive when maximum capacity is desired. Capacity control of thermocompression evaporators depends on the type of compressor positive-displacement compressors can utilize speed control or variations in operating pressure level. Centrifugal machines normally utihze adjustable inlet-guide vanes. Steam jets may have an adjustable spindle in the high-pressure orifice or be arranged as multiple jets that can individually be cut out of the system. 

Several centrifugal cuvet photocentrifuges are commercially available. These instruments use the same theoiy as the disc photocentrifuges but are hmited in operation to the homogeneous mode of operation. 

The X-ray disc centrifuge is a centrifugal version of the gravitational instruments and extends the measuring technique well into the sub- Im-size range. 

Lubricating-oil governor and seal system cleaned Instrumentation and speed control checked Auxiliary heat recovery system Centrifugal Compressors... 

With the introduction of the new instruments, speed is basically taken for granted. It is a very important parameter for reciprocating compressors, however, because speed is one of the factors in generating displaced volume. For the axial and the centrifugal compressor, speed offers a multiple influence. In the fan laws stated in Chapter 5, speed was the common parameter in both capacity and head. In fact, since head is proportional to speed squared, it becomes quite important that the speed be accurate. 

API Standard 672, Packaged, Integrally Geared, Centrifugal Plant and Instrument Air Compressors for General Refinery Services, Second Edition, W shington, D C. American Petroleum Institute, 1988, Reaffirmed 199 . 

Cost information About 100 per ml kit. < 10/patient use with appropriate preexisting instrumentation and equipment. 100-150 per 1 ml kit. Requires centrifuge to obtain autologous plasma. 120 per ml kit. 

Figure 12-61D. Centrifugal compressor surge control schematic diagram shows instrumentation required when primary flow-measuring device is located in centrifugal compressor discharge line. Symbols T = temperature P = pressure A = differential across compressor outlet to inlet. See Reference 89 for a detailed discussion. (Used by permission White, M. H. Chemical Engineering, p. 54, Dec. 25,1972. McGraw-Hill, Inc. All rights reserved.)...

Ensure that the actual instrument configuration conforms to what is written under Experimental supplier, models, modifications, consumables (HPLC or GC columns, gaskets, etc.), and software for the main instrument, peripherals (injectors, integrators, computers, printers, plotters, etc.), and ancillary equipment (vortexer, dispensers, balances, centrifuges, filters, tubing, etc.). 

At present, several of the instruments which are being utilized for enzyme analysis, such as the centrifugal analyzers (15), have been measuring samples of the order of 5 pi. 

In the case of the capillary blood, it is extremely important that the specimen not be allowed to stand for extensive periods of time before centrifugation. If the blood is to be transferred to the pH meter, then the collecting tube is sealed at both ends during transportation. It is then aspirated into the pH instrument as soon as practicable since one needs a smooth even flow in order to aspirate a specimen into the conventional micro pH meter. After the whole blood has been sampled for various purposes, it is important that the remaining blood be centrifuged promptly. If not, it will clot. Subse-quentially, centrifuging with a clot will tend to hemolyze the blood. Erythrocytes will adhere to the wall and as they are pulled down by the clot, they will be ruptured. Those who do not observe these precautions will find that it is rather difficult to obtain unhemolyzed blood. 

With the development of new instrumental techniques, much new information on the size and shape of aqueous micelles has become available. The inceptive description of the micelle as a spherical agglomerate of 20-100 monomers, 12-30 in radius (JJ, with a liquid hydrocarbon interior, has been considerably refined in recent years by spectroscopic (e.g. nmr, fluorescence decay, quasielastic light-scattering), hydrodynamic (e.g. viscometry, centrifugation) and classical light-scattering and osmometry studies. From these investigations have developed plausible descriptions of the thermodynamic and kinetic states of micellar micro-environments, as well as an appreciation of the plurality of micelle size and shape. 

Improved Methods for Collection, Bioassay, Isolation, and Characterization of Compounds. Techniques used to characterize natural products are evolving rapidly as more sophisticated instrumentation is developed. Plant physiologists and chemists should work closely together on this aspect, since rapid and reproducable bioassays are essential at each step. There is no standard technique that will work effectively for every compound. Briefly, isolation of a compound involves extraction or collection in a appropriate solvent or adsorbant. Commonly used extraction solvents for plants are water or aqueous methanol in which either dried or live plant parts are soaked. After extracting the material for varying lengths of time, the exuded material is filtered or centrifuged before bioassay. Soil extraction is more difficult, since certain solvents (e.g. bases) may produce artifacts. 

Active Air Sampling Active air sampling provides quantitative data because air at a known flow rate is impacted on a strip of nutrient media, followed by incubation of the nutrient strips and enumeration of colonies. Common active air sampling instruments include the slit-to-agar impact sampler and the centrifugal (Reuter) sampler. 

Centrifugal partition chromatography (CPC) has been used to characterize the partitioning behavior of hydrophilic molecules, where log D values as low as —3 can be obtained [371,377-379]. It is not as popular a method as it used to be, apparently due to instrumental challenges. Cyclic voltammetry (CV) has become the new method used to get access to very low log D values, with partition coefficients reported as low as —9.8 [261,269,362]. 

He et al. (2002) used an off-line HPLC/CE method to map cancer cell extracts. Frozen ovarian cancer cells (containing 107 cells) were reconstituted in 300 pL of deionized water and placed in an ultrasonic bath to lyse the cells. Then the suspension was centrifuged and the solubilized proteins were collected for HPLC fractionation. The HPLC separation was carried out on an instrument equipped with a RP C-4 column, 250 mm x 4.6 mm, packed with 5-pm spherical silica particles. Extracted proteins were dissolved in 300 pL of DI water, and lOOpL was injected onto the column at a flow rate of 1 mL/min. Buffer A was 0.1% TEA in water and buffer B was 0.1% TFA in acetonitrile. A two-step gradient, 15-30% B in 15 min followed by 30-70% B in 105 min, was used. The column effluent was sampled every minute into a 96-well microtiter plate with the aid of an automatic fraction collector. After collection, the fractions were dried at room temperature under vacuum. The sample in each well was reconstituted before the CE analysis with 10 pL deionized water. The... 

---