Drying by vacuum

A flask charged with A-carboxyanhydrides of tyrosine (14.5 mmol), alanine (72.1 mmol), y-methoxyglutamate (22.2 mmol), and e-A-Boc-lysine (51.5 mmol) were treated with 583.3 ml of dioxane and then stirred for 30 minutes and treated with 116 jlL of diethyl amine. Within the first hour the mixture became viscous and very cloudy. After 24 hours the mixture was quenched by pouring into a second flask containing 1.58 liter of water and awhile colored solid collected. The precipitate was dried by vacuum filtration and washed six times with 250 ml of water and then dried overnight and the product isolated. 

A mixture of 24.5 g 9-(2-dimethylaminoethyl)-9-hydroxymethyl-10-(methylacridan) 1 L of m-xylene and 125.0 g phosphorus pentoxide are refluxed for 3 h the reacture mixture is cooled, poured on to ice, agitated for 15 min, alkaline by the addition of sodium hydroxide solution, and extracted with ethyl acetate the organic phases are washed with water, dried over magnesium sulfate, and dried by vacuum distillation. The residue is dissolved in ether, filtered, and concentrated to a small volume pentane is added with distillation to remove the ether. The mixture is filtered and concentrated to about 100 ml crystallization is allowed to commence and the mixture is... 

A typical Mazzoni fatty acid neutralization soap plant is illustrated in Fig. 36.5.6 The operation of this plant involves the pumping of the reactants through preheaters to a turbodisperser, or high-shear mixer, where the contact of the reactants with each other initiates the formation of neat soap. The soap mass, which is partially reacted at this stage, then proceeds to the mixer where it is recirculated until the neutralization is complete. The completion of the neutralization reaction is monitored continuously by an electric potential (millivolt, mV) measurement for alkalinity. The neat soap is then dried by vacuum spray-dryers, as described earlier, to produce soap pellets ready for finishing into soap bars. 

The diazonium salt that should be used in this experiment is benzenediazonium fluoborate (C6H5N2BF4, M = 191.9). The great majority of diazonium salts are notoriously unstable solids and ean deeompose with explosive violence. The fluoborates are by far the safest to use and are not known to explode however, reasonable caution should be used in preparing the compound. Since even benzenediazonium fluoborate will decompose slowly, it should not be prepared too far in advance, and it must be stored in a refrigerator. A simple high-yield procedure for its preparation has been given by Dunker, Starkey, and Jenkins. Recrystallization of the product from 5 percent fluoboric acid yields white needlelike crystals, which can be dried by vacuum pumping at 1 Torr for several hours, t... 

D. Grieff and W. A. Rightsel, Stabilities of suspensions of virus after freezing or drying by vacuum sublimation and storage. Cryobiology i(6) 432 44, 1967. 

The typical cleaning sequence of a reusable cuvet and/or reaction vessel Involves aspiration of the reaction mixture out of the cuvet at an in situ wash station. A detergent, alkaline, or acid wash solution is then repeatedly dispensed into and aspirated out of the cuvet. The cuvet is rinsed several times with deionized water and dried by vacuum or pressurized air. Optical clarity is verified automatically in most systems (usually while the cuvets contain the water). If performance is unsatisfactory, the operator is alerted to replace individual cuvets. If the cuvets are not replaced promptly, the system cannot be used for analysis until they are replaced, the results for the unsatisfactory cuvets will be flagged. 

While there are other solvents that may also be used effectively with reversed-phase sorbents, these solvents are capable of dissolving the range of compounds that are generally isolated by SPE. If more hydrophobic solvents are used in bonded-phase SPE, then the sorbent must be carefully dried by vacuum to remove all traces of water in the silica matrix in order that the eluting solvent can interact with all areas of the sorbent and not be stopped by residual water trapped in the pores. If this is not done, then the hydrophobic solvent (let us say, methylene chloride) will not effectively wet the surfaces of the C-18 bonded phase and poor recoveries will result. If methanol, acetonitrile, or ethyl acetate is used, then complete drying of the sorbent is not required because the solvent will either be miscible with water (methanol and acetonitrile) or displace the water from the silica (ethyl acetate). 

Ui The enzymatic charge offered for immobilization in U/g of support, U t the enzymatic charge theoretically immobilized in U/g of support, R1 the immobilization yield, defined as (C/rr/Ui)x 100, U i the measured immobilized enzyme activity, in U/g of biocatalyst, RA the activity recovered in the immobilized enzyme, defined as (Uei/[/it)=< 100, Note I gelation/encapsulation=45 °C, ethanolic/acid medium, 155 min, aging=18 h at 4 °C, drying=suck dried by vacuum, followed by a 24-h resting period in a desiccator All the results of this immobilization are the averages of duplicates. 

MBHA resin, 3.0 g (>0.2 mmol/g), is added to a filtered assembly suitable for manual peptide synthesis. DCM is added and the resin is allowed to swell for 1 h. DGM should completely cover the resin. DCM is removed by vacuum filtration and the (DCM/DIEA) solution is added to neutralize the resin. After 1 min the base solution is removed by filtration and this treatment is repeated. The resin is washed with DCM and air dried by vacuum filtration for 5 min. 

C) for each solvent, respectively. The extracts were dried by vacuum distillation. The extraction yields are defined as ... 

Various test methods for moisture were screened. An optimum method for determining moisture absorption and diffusion through the polymer was selected. This method involved tracking the weight changes of a small polymer sample on a McBain balance when subjected to 100% relative humidity at constant temperature. The sample was first dried by vacuum in the balance. Any weight gain by the sample when exposed to 100% relative humidity would allow for the calculation of the material s moisture permeability rate. 

Figure 6 AMD 2 with a syringe (8) via the motorized valve (1) the selected portions of solvent are taken from the storage bottles (15) and delivered to the chamber (9). When the mobile phase has reached the programmed height on the plate (10) the chamber is drained into the waste bottle (16) and the plate is dried by vacuum from a pump (18). Vacuum is released through conditioning bottles (6, 7) allowing adjustments to the gas phase in the chamber, (photograph courtesy of CAMAG.)...

A schematic representation of this method is also shown in Fig. 1. Neat AlEl, was added dropwise to neat Ti(0-/i-Bu)4 in a Schlenk flask. The flask had been precooled on an ice bath to avoid an evolution of heat due to rapid exothermic complex formation between Ti(0- -Bu)4 and AlEtj. The catalyst was then subjected to aging at room temperature for 1 h, followed by high-temperature aging (150°C) for 1 h. The flask was then degassed and the catalyst was coated on the inner wall of the flask by rotating it. After cooling the flask with a dry ice and ethanol mixture (-78°C), acetylene gas was introduced into it. The polymerization was carried out for 0.5-1 h. The polyacetylene film prepared was washed several times with toluene cooled at -78 C and dried by vacuum pumping. We emphasize here that all procedures from the catalyst preparation to the end of polymerization are free of solvent. 

Important new instruments were developed after the UM chamber, aimed at increasing the efficiency of TLC through improvement of the separation mechanism. Programmed multiple-development TLC as elaborated by Perry (12) combines the techniques of continuous multiple development and evaporation. Recently this technique was improved by Burger (13). In this system the chomato-plate is developed several times in the same direction with various eluents of decreasing elution power. Between developments the chromatoplate is dried by vacuum. This method is termed automated multiple development (AMD) (14). High-performance TLC (HPTLC) is based on the use of chromatoplates coated with fine particles of narrow particle size distribution sorbent and is carried out with sophisticated instrumentation (15,16). 

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