Solvent collection system

Choose initial positions for the atoms. For a molecule, this is whatever geometry is available, not necessarily an optimized geometry. For liquid simulations, the molecules are often started out on a lattice. For solvent-solute systems, the solute is often placed in the center of a collection of solvent molecules, with positions obtained from a simulation of the neat solvent. 

Application of the Solvent Formulation System. In contrast to the acrylic polymerization model discussed previously which is extremely complex mathematically and computation wise the solvent formulation system is a growing collection of models which are much less complex mathematically and computation wise. However, the system does allow one to evaluate many properties of solvent blend quickly and with relative ease. The system has been found to be valuable in ... 

Figure 1 is a schematic representation of the wet oxidation micro-pilot plant. The system consists of three sections, an electrically heated oxidation vessel, a high pressure solvent delivery system, and a water cooled depressurization and collection chamber. A more detailed description of the pilot plant can be found in previous publications (3,4). 

The HPLC-FTIR technique has recently been used to identify six catechins and two methyl-xanthines present in green tea extracts." " A reversed-phase separation of the compounds was performed on a C-18 column equilibrated at 30°C using an isocratic mobile phase of acetonitrile-0.1% formic acid (15 85), prior to introduction to the deposition interface linked to the FTIR detector. The solvent was evaporated at 130°C and spectra were collected every 6 sec during the run. Two distinct designs for HPLC-FTIR interfaces have been developed flow cells and solvent elimination systems. Flow cell systems acquired spectra of the eluent in the solvent matrix through IR transparent, nonhydroscopic windows. The... 

The use of small columns such as microbore liquid chromatographic columns, requiring smaller sample size, and computer-controlled solvent delivery and collection systems should lead to the development of fully integrated and automated cleanup systems. Small sample sizes facilitate miniaturization of sample preparation procedures, which in turn brings several benefits including reduced solvent and reagent consumption, reduced processing time, less demand for bench space, and ease of automation. 

Variable wavelength UV/VIS spectrophotometer suitable for detection at 654 nm Chromatographic data collection system Precolumn solvent filter... 

The fraction of column effluent containing the analyte and internal standard can be either collected manually for subsequent reinjection onto the second (analytical) column (offline operation) or diverted directly onto the second column via a high-pressure switching valve (online operation). For manual collection, a drop-counter-fraction collecting system rather than a volume collection system has been recommended (117). The fraction is collected in a small tapered tube, and the solvent is carefully evaporated off under a stream of nitrogen. The residue is then dissolved in a small volume of a suitable solvent for the analytical separation. Because the sample is reconstituted in offline operation, the potential problem of mobile phase incompatibility between the two HPLC systems is avoided, and hence any semipreparative/analytical combination can be used. 

Table 4.2. This does not take account of the solvent supply system or fraction collection arrangements, which will be dependent upon the mode of separation.

In the aerosol solvent extraction system (ASES), the protein is dissolved in a compatible solvent (i.e., water or DMSO) and then introduced by atomization into supercritical CO2 (12,13). The solvent is extracted from the droplet, and the protein precipitates to form particles with appropriate sizes for pulmonary delivery (see Note 3). CO2 is then removed by venting off and the particles are collected. Insulin powders (see Note 4) made by this method possess a mean geometric diameter of 9.6 xm, and 22% of the powder was in the respirable range (0.5-6 p,m) (12). 

Refer to manufacturers solvent delivery system (pump) manual. Since no column is installed, either collect flow from the injector into a suitably sized container or jumper the injector to the detector in order to flush the entire system to waste. 

This fraction should contain no sample as it represents the lag volume in the connecting tube. Some solvent delivery systems may contain a valve for collecting mobile phase effluent. If so, simply turn this selector valve to the collect position. 

Analysis of Phenolic Compounds. A Hewlett-Packard (Palo Alto, CA) Model 1090 HPLC System, was used to determine the levels of specific phenolic components. The HPLC system was equipped with a ternary solvent delivery system, a diode array UV-VIS detector, and HP ChemStation software for data collection and analysis. Full chromatographic traces were collected at 280, 520, 316, and 365 nm, and spectra were collected on peaks. The stationary phase was a Hewlett-Packard LiChrosphere C-18 coliram, 4mm X 250 mm, with 5 pM particle size packing. Operating conditions include an oven temperature of 40 C, injection volume of 25 pL, and flow rate of 0.5 mL/minute. The mefriod was based on a previously published method for phenolic components in wine (30) and used the modified solvent gradient shown in Table II. Solvent A was 50 mM dihydrogen ammonium phosphate, adjusted to pH 2.6 with orthophosphoric acid. Solvent... 

F2). Once the desired compound has been detected by the mass spectrometer, the software will trigger the first fraction collector which will divert the flow into the first fraction vessel (FI) and the desired material will be collected. In this way, the purified material is collected by fraction collector one, the other components from the sample will be collected in a different vessel by fraction collector two and only solvent will be collected into the waste container. Similarly, if the system fails to trigger collection of the desired material, potentially valuable samples would not be lost by virtue of being bulked with other unde.sired entities in a common waste vessel. Instead, the unpurified sample can simply be recovered from the solvent collected in F2 and reprocessed. 

The comparison mentioned under 2. will result in knowledge on which method can reliably be used under which conditions. As other methods might be simpler (in terms of man-hours and equipment needed to perform the measurement) compared to the Guideline or produce online results on-site, we have named them shortcut methods . Examples of these methods are a) the solid phase adsorption (SPA) method developed by KTH (7], b) a number of solvent-free tar collection systems used by BTG, BEF, IGT [8-10] and c) the FID online tar analysing method under development at the University of Stuttgart (11,12]. Currently it is unknown under which conditions these methods give reliable results, for example it is unknown whether the SPA method can be used for updraft gasifier tars and at which conditions the solvent-free methods fail to collect ail tars, for instance as a result of aerosol formation. 

Volatile room temperature condensibles pyrolysis products were collected at cold parts within the reactor and in a collecting system made of a liquid trap followed by a Cambridge filter. The liquid trap contained inhibitor free tctrahydrofiiran (THF) at O C. The filter and the cold parts of reactor were washed with inhibitor free THF. Dry tars were prepared by evaporating the solvent in a vacuum oven at about 45°C. 

Before injecting the first sample some general considerations have to be taken into account with regard to the design of the preparative chromatographic plant. All preparative HPLC plants consist, basically, of the same components (Fig. 5.1) a solvent and sample delivery system, the preparative column and a detection and fraction collection system. 

Gas antisolvent processes can be performed in a semicontinuous mode. In this case the solution and the antisolvent are continuously introduced in the system until the desired amount of the product is formed. The introduction of the solution is then stopped and the DG flux extracts the residual solvent from the system. The system is then depressurized to enable collection of the product. The solution is generally introduced through an atomization nozzle that favors the prompt expansion of the solution and the formation of small particles. Different process configurations have been utilized, i.e., co- and countercurrent introduction of the solution and antisolvent fluxes and various nozzles have been designed. The process is referred to by different acronyms such as ASES (aerosol solvent extraction system), SAS (supercritical antisolvent), SEDS (solution enhanced dispersion by supercritical fluids), PCA (precipitation with a compressed fluid antisolvent), GASR (gas antisolvent recrystallization), GASP (gas antisolvent precipitation). 

When micronic or submicronic particles are produced, particle collection and harvesting is certainly the most acute issue Based on the considerable experience gathered in dust collection at any scale (83), different particle collection systems can be proposed depending on the final form desired by the operator dry powder, dry mixture of active substance and excipient particles, aqueous or solvent suspension. 

Since pressurized fluid extraction (PFE), also known as accelerated solvent extraction (ASE ), is a relatively new technique, the commercial availability of PFE instruments is limited. A commercial PFE system ( ASE 200 ) currently available is a fully automated sequential extractor developed by the Dionex Corporation, USA. This mainly consists of a solvent-supply system, extraction cell, oven, collection system and purge system, all of which are under computer control. A schematic diagram of a PFE system is shown in Figure 7.15. This system (ASE 200) can operate with up to 24 sample-containing extraction vessels and up to 26 collection vials, plus an additional four vial positions for rinse/waste collection. 

The most distinctly different approach to SPE is the use of a disc, not unlike a common filter paper. This SPE disc format is referred to by its trade name of Empore (discs). The 5-10 pm sorbent particles are intertwined with fine threads of PTFE which results in a disc approximately 0.5 mm thick and a diameter in the range 47 to 70 mm. Empore discs are placed in a typical solvent filtration system and a vacuum applied to force the solvent-containing sample through (Figure 8.7). To minimize the dilution effects that can occur, it is necessary to introduce a test-tube into the filter flask to collect the final extract. Manifolds are commercially available for multiple sample extraction using such Empore discs. 

Figure 17.2 The four-state PCET reaction in a solvent coordinate system. The four states are abbreviated with labels according to the initial and final states of the electron (i and f, respectively), and the initial and final states of the proton (a and b, respectively). The coordinates Zj and Zp refer to the collective solvent coordinates that are coupled to ETand PT, respectively. A concerted PCET reaction can...

It also minimizes sample handling, provides fairly clean extracts, expedites sample preparation, and reduces the use of environmentally toxic sol vents.SFE has been applied to the extraction of carcinogenic AAs from soil and sand. The paper studies the possibilities of using MAE and SFE in determination of AAs by HPLC after reduction of the azo colorants. Two SFE pieces of equipment differing in the trapping step (solid-phase trap or solvent collection) were utilized for the extractions. The MAE experiments were then performed with a vessel system with temperature and pressure control. 

It should be noted that the partition ratio at equlibrium predicts the optimum desorption effiency attainable, and other experiments may be necessary to detect nonequlibrium situations. Desorption efficiency should not be taken as the recovery since other factors may have a significant effect. After a solvent/sorbent system is selected and tested using the phase equilibrium technique, direct injections of the test compound are made into collection tubes with and without air being pulled through. If the desorption efficiencies as determined by direct injection are considerably lower than phase equilibrium values, interaction or reaction on the sorbent surface is indicated. If the total recovery from the simulated air collection is lower than the direct injection efficiency (even through no breakthrough has occurred) hydrolysis, oxidation, or another reaction may indicated. 

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