Flow rate enrichment

The liquid and vapour molar flow rate in the enriching section, are denoted by L and V, as previously and in the stripping section as L and V. The relationship between L, V, L and V is determined by the feed rate F and the thermal quality of the feed "q". 

Abstract A preconcentration method using Amberlite XAD-16 column for the enrichment of aluminum was proposed. The optimization process was carried out using fractional factorial design. The factors involved were pH, resin amount, reagent/metal mole ratio, elution volume and samphng flow rate. The absorbance was used as analytical response. Using the optimised experimental conditions, the proposed procedure allowed determination of aluminum with a detection limit (3o/s) of 6.1 ig L and a quantification limit (lOa/s) of 20.2 pg L, and a precision which was calculated as relative standard deviation (RSD) of 2.4% for aluminum concentration of 30 pg L . The preconcentration factor of 100 was obtained. These results demonstrated that this procedure could be applied for separation and preconcentration of aluminum in the presence of several matrix. 

Application of 2 fractional factorial design allowed the optimization of the enrichment procedure for the determination of aluminum by AAS. The optimum conditions were found to be 4 of pH, 10 of reagent/metal mole ratio, 15 luL of elution volume and 1 mL min of flow rate. 

The membrane performance for separations is characterized by the flux of a feed component across the membrane. This flux can be expressed as a quantity called the permeability (P), which is a pressure- and thickness-normalized flux of a given component. The separation of a feed mixture is achieved by a membrane material that permits a faster permeation rate for one component (i.e., higher permeability) over that of another component. The efficiency of the membrane in enriching a component over another component in the permeate stream can be expressed as a quantity called selectivity or separation factor. Selectivity (0 can be defined as the ratio of the permeabilities of the feed components across the membrane (i.e., a/b = Ta/Tb, where A and B are the two components). The permeability and selectivity of a membrane are material properties of the membrane material itself, and thus these properties are ideally constant with feed pressure, flow rate and other process conditions. However, permeability and selectivity are both temperature-dependent... 

Electrospray ionization can be considered as an electrolysis cell (Fig. 1.11) where, in the positive mode, cations are enriched at the surface of the solution and negative ions move inside the capillary. Oxidation of the analyte has been observed at certain occasions, in particular at very low flow rates. Also in the case of... 

Figure 3.5 Measurement of the chiral purity of commercially available Jacobson s catalyst using a cyclodextrin-based CSP. (a) Lower trace / ,/ -enantiomer product upper trace / ,/ -enantiomer product artificially enriched with S -enantiomer and (b) lower trace S. S -enantiomer product upper trace S. S -enantiomer product artificially enriched with / ,/ -enantiomer. (Conditions CYCLOBOND 1 2000RSP 25 cm X 0.46 cm i.d. mobile phase acetonitrile triethylamine glacial acetic acid [1000 0.5 2.5, v/v] flow rate 1 ml/min temperature ambient detection UV at 240 nm sample preparation 1 mg/ml in acetonitrile injection volume 10 fxl). Reprinted from [19], copyright 1998, with permission of Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc.

Figure 3.6 Resolution of the enantiomers of omeprazole using a protein-derived CSP. The chromatogram shows the analysis of esomeprazole API artificially enriched with 0.1% w/w of the R-enantiomer. (Conditions cti-AGP 10 cm X 0.4 cm i.d. mobile phase sodium phosphate [pH 6.0, 60 mM] acetonitrile [85 15, v/v] flow rate 1 mbmin detection UV at 302 nm column temperature ambient sample preparation 0.02mg/ml in sodium phosphate [pH 11.0, 18 mM] methanol [98 2, v/v] injection volume 20 pi.)...

The particle-beam interface is an analyte-enrichment interface in which the column effluent is pneumatically nebulized into a near atmospheric-pressure desolvation chamber connected to a momentum separator, where the high-mass analytes are preferentially directed to the MS ion source while the low-mass solvent molecules are efficiently pumped away (71, 72). With this interface, mobile phase flow rates within the range O.l-l.O ml/min can be applied (73). Since the mobile phase solvent is removed prior to introduction of the analyte molecules into the ion source, both EI and CI techniques can be used with this interface. 

Figure 2. A, chromatogram from elution of 100 mL of enriched drinking water (Athens, GA) fortified with 1, 0.26 pg of caffeine 2, 0.050 gig of m-nitroaniline 3, 0.44 pg of atrazine 4, 0.75 pg of 2,6-dichloroaniline 5, 0.43 fig of N-nitrosodiphenylamine 6, 0.85 pg of decafluorobiphenyl (not detected) and 7, 0.41 pg of disperse red dye 13. B, chromatogram from elution of 100 mL of enriched drinking water (Athens, GA). Conditions for both enrichments 100-mL samples enriched on an ODS-packed precolumn at 5 mL/min. Analytical separation was on Partisil-10, ODS-2, 250-mm X 4.6-mm i.d. column. Mobile-phase gradient was 10% to 90% (v/v) acetonitrile in distilled-deionized water at 5%/min, and flow rate was 1.0 mL/min. Detection was at 254 nm. (Reproduced with permission from reference 17.

Figure 3. Standards recovered from 10 mL of distilled-deionized water on an ODS precolumn. Peak identities 4, 0.14 pg of caffeine 5, 0.20 pg of pentachlorophenol 7, 0.061 pg of m-nitroandine 8, 0.15 pg of atrazine 9, 0.40 pg of quinoline 10, 0.26 pg of 2,6-dichloroaniline 11, 0.14 pg of N-nitrosodiphenylamine and 12, 0.055 pg of pyrene. Conditions for concentration 10-mL sample enriched on an ODS-packed precolumn. Analytical separation was on Zorbax ODS, 250-mm by 4.6-mm i.d. column. Mobile-phase gradient was 100% pH 7,0.1 M acetate buffer for 2 min followed by ramp to 90% acetonitrile/10% pH 7, 0.1 M acetate buffer (v/v) in 20 min at 1.0-mL/min flow rate. Detection was at 254 nm. (Reproduced with permission from reference 18.)...

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