Solvent flow-rate

The flow-rates used in most reported PHSE methods range from 0.5 to 3.0 ml/min. The use of very low flow-rates ( 0.5 ml/min) is not recommended because it may easily lead to blockage of the restrictor used to maintain the pressure in the system on the other hand, flow-rates above 3 ml/min increase dilution of the analytes in the extracts and this causes difficulty in subsequently determining the extracted species [18]. 

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The solvent flow rate to the distillation usually can be varied... 

Since the total gas and Hquid flow rates per unit cross-sectional area vary throughout the tower (Fig. 5) rigorous material balances should be based on the constant iaert gas and solvent flow rates and respectively, and expressed ia terms of mole ratios and X. A balance around the upper... 

The variable that has the most significant impact on the economics of an extractive distillation is the solvent-to-feed (S/F) ratio. For closeboiling or pinched nonazeotropic mixtures, no minimum-solvent flow rate is required to effect the separation, as the separation is always theoretically possible (if not economical) in the absence of the solvent. However, the extent of enhancement of the relative volatihty is largely determined by the solvent concentration and hence the S/F ratio. The relative volatility tends to increase as the S/F ratio increases. Thus, a given separation can be accomplished in fewer equihbrium stages. As an illustration, the total number of theoretical stages required as a function of S/F ratio is plotted in Fig. 13-75 7 for the separation of the nonazeotropic mixture of vinyl acetate and ethyl acetate using phenol as the solvent. 

In case A the solvents are immiscible, so the rate of feed solvent alone in the feed stream F is the same as the rate of feed solvent alone in the raffinate stream R. In like manner, the rate of extraction solvent alone is the same in the stream entering S as in the extract stream leaving E (Fig. 15-12). The ratio of extraction-solvent to feed-solvent flow rates is therefore S /F = E /R. A material balance can be written around the feed end of the extrac tor down to any stage n (see Fig. 15-12) and then rearranged to a McCabe-Thiele type of operating line with a slope of F /S [Eq. (15-11)]. 

Packing Column Solvent Flow Rate Temp ... 

Column Solvent Flow rate Pressure Detector ... 

In this study, four Styragel columns were utilized one column had a nominal porosity rating of 10, two colvtmns of 10, and the fourth column of 10 A. The refractometer was maintained at 37°C. A 5 ml syphon was used to monitor a solvent flow rate of 1 ml/min. The instrviment was run at the highest sensitivity setting because the refractive index difference between our solvent and polymer was only moderate and because a number of samples analyzed had a broad molecular weight distribution (MWD). 

The total solvent flow rate was set to 2.0mlmin . Separate streams of catalyst (0.02 M in toluene) and cocatalyst (0.02 M in toluene) formulations were fed to the tubing reactor in the microliter per minute range by use of special micro-pumps. 

Figure 3.42. Maintenance of raffinate outlet concentration, by regulation of solvent flow rate.

Proportional plus integral control manipulates the solvent flow rate based on the exit solute concentration in the raffinate. Thus G is a function of GO, KC,... 

INTEGRAL TIME CONSTANT BASE SOLVENT FLOW RATE RAFFINATE SET POINT... 

The extent of extraction can be investigated as a function of solvent flow rate. 

ESI-MS is the most successful method of coupling a condensed phase separation technique to a mass spectrometer. Because the input to ESI is a liquid, electrospray serves as an interface between the mass spectrometer and liquid chromatographic techniques, including SEC and CE (capillary electrophoresis). In LC-MS the flow-rate should lie in the range recommended for the HPLC pump and the mass spectrometer (typically 0.001 -l.OmLmin-1). Recent advances in (nano)electrospray technology include the development of the use of very low solvent flow-rates (30 to 1000nLmin-1) [130,131],... 

Much LC-MS work is carried out in a qualitative or semi-quantitative mode. Development of quantitative LC-MS procedures for polymer/additive analysis is gaining attention. When accurate quantitation is necessary, it is important to understand in depth the experimental factors which influence the quantitative response of the entire LC-MS system. These factors, which include solvent composition, solvent flow-rate, and the presence of co-eluting species, exert a major influence on analyte mass transport and ionisation efficiency. Analyte responses in MS procedures can be significantly affected by the nature of the organic modifier used in the RPLC... 

The transfer functions are constants and hence we denote them with the gains Kn and K12. If the solvent flow rate m2 increases, the solute will be diluted. Hence, K12 is negative. 

Figure 4. CSP-HPLC separation of the enantiomers of BaP dihydro- and tetrahydro- trans-7,8-diol and trans-9.10-diol. A column (4.6 mm ID x 25 cm) of y-aminopropylsilanized silica with ionically bonded (R)-N-(3,5-dinitrobenzoyl)phenylglycine was eluted with 18% (v/v) of ethanol/acetonitrile (2 1, v/v) in hexane at a solvent flow rate of 2 ml/min.(Reproduced with permission from Ref. 20.

This chapter reviews recent findings about the health benefits of phytochemicals present in fruits, vegetables, nuts, seeds, and herbs, including phenolics, carotenoids, sterols, and alkaloids. These phytochemicals are extracted using emerging technologies such as supercritical carbon dioxide (SC-CO2) extraction, PEF, MWE, HPP, UE, and OH. The impact of important parameters related to sample preparation (particle size and moisture content) and extraction process (temperature, pressure, solvent flow rate, extraction time, and the use of a cosolvent) on the efficiency of extraction and on the characteristics of the extracted products is evaluated based on an extensive review of recent literature. The future of extraction of phytochemicals is certainly bright with the... 

Flow rate and extraction time. Decreasing solvent flow rate results in an increased of extraction yield using SC-CO2. The extraction time is a function of the matrix structure, differing with the type of material. For example, diffusion through a nut is faster than that through a seed. Time is inversely related to the particle size, and many other process parameters can influence this variable, such as temperature, pressure, flow rate, and cosolvent addition (Saldana 1997 Saldana and others 2002a,b Mohamed and others 2002). 

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