High-speed separator

It is seen from Figure 15 that the analysis time ranges from about 10,000 seconds (a little less than 3 hr) to about 30 milliseconds. The latter, high speed separation, is achieved on a column about 2 mm long, 12 microns in diameter, operated at a gas velocity of about 800 cm/second. Such speed of elution for a multicomponent mixture is of the same order as that of a scanning mass spectrometer. 

Plate valves are typically used for high speed separable compressors. Plate valves are similar to ring valves with the rings connected by ribs. Instead of individual elements opening and closing, all valve ports o[)en and close at the same time. 

As previously discussed in this chapter and in Chapter 10, reciprocating compressors are generally classified as either low-speed (integral) compressors or high-speed (separable) compressors, API has provided a standard and specification for each type of compressor to help the user and the facility engineer provide reliable compressor installations. 

API Specification IIP Specification for Packaged Reciprocating Compressors for Oil and Gas Production Services covers packaged high-speed separable compressors with speeds from 600 to 1,200 rpm. The majority of reciprocating compressors sold in today s market fall into this category. 

The advantages of monosized chromatographic supports are as follows a uniform column packing, uniform flow velocity profile, low back pressure, high resolution, and high-speed separation compared with the materials of broad size distribution. Optical micrographs of 20-p,m monosized macroporous particles and a commercial chromatography resin of size 12-28 p,m are shown in Fig. 1.4. There is a clear difference in the size distribution between the monodispersed particles and the traditional column material (87). 

Remarks Moderate selectivity Moderate separation speed Narrow mobile-phase selection Fow selectivity High-speed separation Most generous mobile-phase selection Fow selectivity High-speed separation Generous mobile-phase selection Best for high MW polymers Thermal gradient may be programmed for broad MW separation... 

High speed separations, particularly with narrow-bore HCOT columns of 100 aicroneters or less, places special demands upon the instrument design [131,134,148-150]. The gas chromatograph... 

A high-speed separation of tryptic peptides of horse cytochrome c is shown in Figure 6. As the temperature and flow rate were increased, the separation substantially improved, an observation consistent with data demonstrating that conformational issues may be increasingly important factors in peak broadening as the time scale of the chromatography approaches that... 

Solid-phase microextraction (SPME) is compatible with high-speed separations. SPME-IR has been applied to VOCs in soil [156]. G6recki and Pawliszyn [69] reported separation of 28 volatile organic compounds listed in EPA method 624, with ITMS detection, in less than 150 s. 

As mentioned earlier, high-speed separation is necessary to carry out fast, comprehensive 2D HPLC. The polymer monoliths have not been employed in such 2D HPLC, probably because permeability of polymer monoliths is not high enough to allow fast elution of the second dimension (2nd-D) in simple 2D operation, and the gradient cycle at the 2nd-D cannot be so fast to allow online 2D operation without reducing peak capacity at first dimension (lst-D). 

Development of short monolithic silica columns with high efficiencies (up to 200.000 plates per meter) and high-speed separations, performance parameters that can be obtained with column packed with sub-2 pm particles, but achieved with monolithic silica columns at very lower system back-pressure. 

It was thought that high-speed separations would be achieved by the development of a physically stable pumping system and highly sensitive detectors ... 

High-speed separations can be achieved with a short column packed with 3 pm stationary phase material, as shown in Figure 1.2. The sensitivity was also improved by the use of smaller-size stationary phase materials, due to less sample diffusion inside the column. The following conditions are required to obtain such a separation. 

Effenhauser, C. S., Paulus, A., Manz, A., and Widmer, H. M. (1994). High-speed separation of antisense oligonucleotides on a micromachined capillary electrophoresis device. Anal. Chem. 66, 2949-2953. 

High efficiency columns currently available for gel permeation chromatography of small molecules and oligomers provide high speed separations. The use of multiple detectors provides additional information which facilitates characterization and determination of the separated species. 

Jacobson, S. C., R. Hergenroder, L. B. Koutny, and J. M. Ramsey. High-speed separations on a microchip. Anal. Chem. 66, 1114-1118 (1994b). 

Non porous silica particles (NPS) with diameters of around 1.5 jm are used in high-speed separations [11]. Retention takes place here only at the geometrical surface, which amounts to 3 m /g. By the preparation process, uniform spherical particles with narrow size distribution are obtained. 

Elevated Temperature HPLC for High-Speed Separation—Effects on Viscosity... 

ELEVATED TEMPERATURE HPLC FOR HIGH-SPEED SEPARATION-EFFECTS ON VISCOSITY AND COLUMN EFFICIENCY... 

Finally, the fourth element is a widened scope of application. The fact that LC/MS is now routinely used during every stage of drug development is a powerful benchmark for acceptance. The increased performance of applications that incorporate LC/MS have, in turn, stimulated new performance levels for sample preparation, high speed separations, automated analysis, information databases, and software tools, to name a few. Motivated by unmet industry needs, the drive for new applications has stimulated tremendous growth in pharmaceutical analysis marked by invention and creativity. 

Despite the attraction of high-speed separations, the choice of whether to use standard-bore HPLC or small-bore HPLC is mostly governed by practical considerations (the need for a detector capable of providing positive identifications), environmental considerations (low solvent consumption), sample size considerations (small injection volumes), or price considerations (the need to use exotic solvents and expensive samples, such as DNA). Simple separations are best carried out in conventional short, wide columns, whereas more difficult separations can be achieved with the use of longer, narrower columns.15 However, difficulties arise when downscaling HPLC. The difficulties are divided into theoretical and practical considerations. 

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