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Extraction Column (extraction + column)

Distribution by Scientific Domains

Chemistry	90%

Selected Abstracts

New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid-Liquid Extraction Column

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2007
M. Ismail Al-Rahawi
Abstract Sauter mean drop sizes (d32) generated from a hole distributor in liquid extraction RDC columns were studied under various conditions. Experiments were designed to generate data required to determine the main variables that control the drop sizes in RDCs. Two precise correlations were proposed for predicting d32 in a RDC extraction column. The first was based on operating variables, hole-distributor diameter, disc speed, column geometry, and system physical properties. The second one considered the same variables, except the column geometry. This model can be used for design purposes. The two correlations are the first of their type to consider the distributor hole inlet diameter in a RDC column. This diameter has been neglected by previous investigators. The maximum standard deviation for all data is 0.75,%, with a maximum absolute error of 6.8,%. [source]

A Genetic Algorithm Based Approach to Coalescence Parameters: Estimation in Liquid-Liquid Extraction Columns

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2006
A. Hasseine
Abstract The population balance model is a useful tool for the design and prediction of a range of processes that involve dispersed phases and particulates. The inverse problem method for the droplet population balance model is applied to estimate coalescences parameters for two-phase liquid-liquid systems. This is undertaken for two systems, namely toluene/water and n-butyl acetate/water in a rotating disc contactor (RDC), using a droplet population balance model. In the literature, the estimation procedure applied to this problem is often based on the deterministic optimization approach. These methods generate instabilities near a local minimum, inevitably requiring information about the derivatives at each iteration. To overcome these limitations, a method providing an estimate for the coalescences parameters is proposed. It is based on a simple and adapted structure of the genetic algorithm, for this particular problem. The agreement between the experimental observations and the simulations is encouraging and, in particular, the models used have proven to be suitable for the prediction of hold-up and Sauter diameter profiles for these systems. Finally, these results demonstrate that the optimization procedure proposed is very convenient for estimating the coalescences parameters for extraction column systems. [source]

Determination of 17,-estradiol in bovine plasma: development of a highly sensitive technique by ion trap gas chromatography,tandem mass spectrometry using negative chemical ionization,

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2002
Giancarlo Biancotto
Abstract A novel approach to the determination of 17,-estradiol in bovine plasma is presented. The observed enhanced sensitivity is gained by the application of tandem mass spectrometry (MS) fragmentation to a stable, well characterized negative ion produced by chemical ionization (methane as reagent gas). A specific derivatizing reactant is employed (pentafluorobenzyl bromide), combined with bis-trimethylsilyltrifluoroacetamide, to favor the formation of a diagnostic precursor negative ion. Plasma samples are purified through a C18 solid phase extraction column and derivatized before gas chromatography,MS analysis. The accuracy and the precision of the method, tested over a set of spiked samples, were satisfactory. The limit of detection was found to be 5 pg ml,1 and the limit of quantification was fixed at 20 pg ml,1. The fragmentation pattern is fully explained and the method is applicable for the official analysis of bovine plasma for the detection of 17,-estradiol according to the European criteria 256/93 and to the draft SANCO/1805/2000 rev. 3. The quantification of incurred positive samples was performed according to the proposed procedure and compared with the results obtained by standardized radio immuno assay; the estimated concentrations were significantly similar. Copyright © 2002 John Wiley & Sons, Ltd. [source]

A direct injection high-throughput liquid chromatography tandem mass spectrometry method for the determination of a new orally active ,v,3 antagonist in human urine and dialysate

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2003
Wei Zeng
A generic high-throughput liquid chromatography (HTLC) tandem mass spectrometry (MS/MS) assay for the determination of compound I in human urine and dialysate (hemodialysis) was developed and validated. By using the HTLC on-line extraction technique, sample pretreatment was not necessary. The sample was directly injected onto a narrow bore large particle size extraction column (50,×,1.0,mm, 60,,m) where the sample matrix was rapidly washed away using a high flow rate (5,mL/min) aqueous mobile phase while analytes were retained. The analytes were subsequently eluted from the extraction column onto an analytical column using an organic-enriched mobile phase prior to mass spectrometric detection. The analytes were then eluted from the analytical column to the mass spectrometer for the determination. The linear dynamic range was 2.0,6000,ng/mL for the urine assay and 0.1,300,ng/mL for the dialysate assay. Intraday accuracy and precision were evaluated by analyzing five replicates of calibration standards at all concentrations used to construct the standard curve. For the urine assay, the precision (RSD%, n,=,5) ranged from 1.9 to 8.0% and the accuracy ranged from 87.8 to 105.2% of nominal value. For the dialysate assay, the precision (RSD%, n,=,5) ranged from 1.1 to 10.0% and the accuracy from 94.5 to 105.2% of nominal value. In-source fragmentation of the acyl glucuronide metabolite (compound III) did not interfere with the determination of parent compound I. The developed HTLC/MS/MS methodology was specific for compound I in the presence of compound III. Column life-time is increased and sample analysis time is decreased over traditional reversed-phase methods when direct injection assays for urine and dialysate are coupled with the technology of HTLC. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Direct-injection high performance liquid chromatography ion trap mass spectrometry for the quantitative determination of olanzapine, clozapine and N -desmethylclozapine in human plasma

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2002
Manfred Kollroser
A specific and sensitive direct-injection high performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) method has been developed for the rapid identification and quantitative determination of olanzapine, clozapine, and N -desmethylclozapine in human plasma. After the addition of the internal standard dibenzepin and dilution with 0.1% formic acid, plasma samples were injected into the LC/MS/MS system. Proteins and other large biomolecules were removed during an online sample cleanup using an extraction column (1,×,50,mm i.d., 30,µm) with a 100% aqueous mobile phase at a flow rate of 4,mL/min. The extraction column was subsequently brought inline with the analytical column by automatic valve switching. Analytes were separated on a 5,µm Symmetry C18 (Waters) analytical column (3.0,×,150,mm) with a mobile phase of acetonitrile/0.1% formic acid (20:80, v/v) at a flow rate of 0.5,mL/min. The total analysis time was 6,min per sample. The inter- and intra-assay coefficients of variation for all compounds were <11%. By eliminating the need for extensive sample preparation, the proposed method offers very large savings in total analysis time. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Evaluation of 3-hydroxy-3-methylglutaryl-COA-reductase, cholesterol-7, -hydroxylase and acyl-COA:cholesterol acyltransferase activities: alternative chromatographic methods to separate metabolites

BIOMEDICAL CHROMATOGRAPHY, Issue 9 2004
Alain Montoudis
Abstract Alternative HPLC and solid-phase extraction column methods were developed to separate metabolites of enzymes involved in cholesterol metabolism in rabbit liver microsomes: hydroxyl-methylglutaryl-CoA reductase, cholesterol-7, -hydroxylase and acyl-CoA:cholesterol acyltransferase. A comparison method of thin-layer chromatography and solid-phase extraction column were assayed to separate substrate and metabolite of hydroxy-methylglutaryl-CoA reductase, whereas for cholesterol-7, -hydroxylase and acyl-CoA:cholesterol acyltransferase, this comparison was done between thin layer chromatography and HPLC. The results obtained by the new analytical chromatographic methods are not signi,cantly different than those observed in literature. Moreover a larger percentage recovery was obtained for analysed metabolites. Our results demonstrate the reliability of these alternative chromatographic techniques and showed that they are valuable tools to precisely and rapidly measure the activity of those enzymes. Copyright © 2004 John Wiley & Sons, Ltd. [source]

New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid-Liquid Extraction Column

Terminal and transient drop rise velocity of single toluene droplets in water

AICHE JOURNAL, Issue 1 2010
Mirco Wegener
Abstract The knowledge of the drop rise velocity in dispersed systems is of fundamental importance. Especially, the residence time is needed for calculation of mass transfer rates in extraction columns. This work deals with fluid dynamic measurements of toluene droplets rising in water ranging from 1.0 to 7.0 mm, with the premise of high purity of the used chemicals. The toluene/water-system is widely used as a test system with high interfacial tension. A semiempirical correlation for pure systems to predict the terminal velocity of single rising/falling droplets based on experimental data is presented. Results show that a distinction between maximum and characteristic mean values of the drop rise velocity is necessary, especially in the diameter range 2.4,3.0 mm where unexpected velocity fluctuations occur. Two distinct terminal rise velocities were observed for 3 mm droplets. Furthermore, comparisons of the Weber-Reynolds-correlation and the drag coefficient with correlations from literature show good agreement. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

A high-rate perfusion bioreactor for plant cells

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2006
C. De Dobbeleer
Abstract A perfusion bioreactor allowing continuous extraction of secondary metabolites was designed and challenged for Eschscholtzia californica plant cell suspensions. Four sedimentation columns mounted inside a 2.5-L bioreactor separated single cells and cell aggregates from the culture medium. Cells were elicited with chitin at day 4 and the liquid medium free of cells and debris was then continuously pumped to the extraction columns containing fluidized XAD-7 resins, and then recirculated back to the cell suspension. A medium upward velocity corresponding to cell sedimentation velocity maintained a stable cell/medium separation front in the columns for sedimented cell volume (SCV) of 90% (70% packed cell volume, PCV). Two perfusion bioreactor cultures of 10 and 14 days were performed. A maximum dilution rate of 20.4/day was reached from day 4 to day 6, and was then reduced to 5/day at day 9 for 55% SCV. Control cultures were performed without and with free extraction resins into the cell suspension. Perfusion cultures showed similar specific growth rates of 0.24,±,0.04/day before and after elicitation. However, production level in the perfusion cultures was similar to that from the culture without resins with a maximum of 2.06 µmole/gDW total alkaloids, with 1.54 µmole/gDW in the resins. Cultures with free resins resulted in 30.94 µmole/gDW with 28.4,±,8.8 µmole/gDW in the resins. Difference in the cells nutritional state from elicitation was identified as a major cause in the production reduction. However, pathway to chelilutine was favored in the continuous extraction culture. © 2006 Wiley Periodicals, Inc. [source]