Centrifuge analyzer

Another automated approach to kinetic analyses is the centrifugal analyzer, a partial cross section of which is shown in Figure 13.9. In this technique the sample and reagents are placed in separate wells oriented radially around a circular transfer disk attached to the rotor of a centrifuge. As the centrifuge spins, the... 

Flow injection analysis (FIA) was developed in the mid-1970s as a highly efficient technique for the automated analyses of samples. °> Unlike the centrifugal analyzer described earlier in this chapter, in which samples are simultaneously analyzed in batches of limited size, FIA allows for the rapid, sequential analysis of an unlimited number of samples. FIA is one member of a class of techniques called continuous-flow analyzers, in which samples are introduced sequentially at regular intervals into a liquid carrier stream that transports the samples to the detector. ... 

Fat Content of Milk. Raw milk as well as many dairy products are routinely analyzed for their fat content. The Babcock test, or one of its modifications, has been a standard direct measure for many years and is being replaced by indirect means, particularly for production operations. The Babcock test employs a bottle with an extended and caHbrated neck, milk plus sulfuric acid [7664-93-9] to digest the protein, and a centrifuge to concentrate the fat into the caHbrated neck. The percentage of fat in the milk is read direcflv from the neck of the bottle with a divider or caHper, rea ding to... 

These concepts are used to analyze separations in the botde centrifuge, the imperforate bowl centrifuge, and the disk centrifuge. Separation by density difference in other types of centrifuges can be analyzed by analogy. 

After centrifugation, the specimens are placed in a holder specifically designed to work with a particular instmment. Some clinical analyzers utilize... 

On all centrifuges that handle flammable solvent, the oxygen content should be continuously monitored. At the very least, it should be checked every shift with a portable analyzer. In addition, the flow of nitrogen should be adequate, clearly visible, and read regularly. 

Data from an existing collection system were analyzed for failure modes and distribution. The results of Pareto analyses indicate the principal causes of failure. A few values of mean times to maintenance action (MTBM) are given for ethylene plant pumps (85 electric driven centrifugal pumps over a 19-month period), and ethylbenzene-styrene monomer plant equipment from 10 months data 4 gas compressors, 3 screw conveyors, 121 pumps, and 235 other items... 

Liquid samples might appear to be easier to prepare for LC analysis than solids, particularly if the compounds of interest are present in high concentration. In some cases this may be true and the first example given below requires virtually no sample preparation whatever. The second example, however, requires more involved treatment and when analyzing protein mixtures, the procedure can become very complex indeed involving extraction, centrifugation and fractional precipitation on reversed phases. In general, however, liquid samples become more difficult to prepare when the substances are present at very low concentrations. 

The density change on polymerization is typically about 20%, and this density gradient can cause significant secondary flows and natural convection effects. The experiments cited above for vinyl acetate polymerization were performed in a helical reactor. The centrifugal force in helical reactors induces secondary flows as well. The effects of helical flow have been analyzed, but were found to be less significant than the effects of natural convection [14]. 

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. 

Figure I. Front view of the miniature centrifugal analyzer. The mechanical, analytical, and optico-electronic components are in one compact unit. Digital data reduction is in another unit, not shown, Courtesy of Dr, Carl A, Burtis, of the former Oak Ridge National Laboratory),...

Harvey, M. Measurement of erythocytes glucose-6-phosphate dehydrogenase activity with a centrifugal analyzer. Clin. Chem. (1975), 134-138. 

An area worthy of study is the development of systems of increasing sample throughput beyond the single column operation. Scott has introduced a prototype multicolumn system based on the centrifugal analyzer principle (53). In this set-up a series of LC colimns is rotated on a disc, with sample delivery at the center of the disc and elution and spectrophotometric analysis on the outside. He has suggested using affinity columns for rapid serum protein analysis by this approach. Of course, other principles, such as segmented flow, could be envisioned in an automated LC system as well. Undoubtedly, we can expect to see the availability of such systems in the next few years. 

Another sedimentation method used is the so-called MSA-analyzer. If the value of "g" in 5.10.8. is increased (such as the use of a centrifuge) one can analyze the very smaU particles in any given distribution in a short time. The problem of course lies in accurate determination of the weight accumulated at a given time under a specific centripetal force. This problem has been neatly solved by careful design of the sedimentation tube, as shown in the following diagram ... 

Soy cell wall material (Soy CWM) was isolated by Alcalase treatment and jet cooking (115°C, 4 minutes) of soy meal followed by centrifugation and recovery of insolubles. Aliqots of 1% suspensions of soy CWM in O.IM acetate buffer pH 5.0 were incubated with enzymes (40pg of each to 1.5 ml of substrate) at 30°C for 24 hours and the solubilized material was analyzed by HPSEC and HPAEC. 

Gel chromatography on Sephadex GlOO (2.8x50cm) of polysaccharide fraction I (Sample 2). The polysaccharide fraction was dissolved in a phosphate buffer at pH 6. After centrifugation, the supernatant was applied to the column at a flow rate of 0.8 ml/min. The elution was performed with a phosphate buffer and fractions of 10 ml each were collected. The refraction of each fraction was measured interferometrically. Fractions with coincident peaks were collected and analyzed for content of galacrturonic acid, neutral sugars and protein. 

A site at the Agricultural Experimental Station (Ithaca, NY) was treated in microcosms with C-labeled glucose, phenol, caffeine, and naphthalene. Levels of C02 were measured to assess utilization of the substrates, and the populations analyzed by separating the C-labeled DNA by density centrifugation, followed by PCR amplification and sequencing of 16S rRNA (Padmanabhan et al. 2003). Populations contained relatives to a range of bacteria that varied with the substrate. Only relatives of Acinetobacter were found in all samples, and for caffeine only Pantoea. 

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