Filtration and degassing

The potential danger for flask implosion during vacuum filtration and degassing should be noted. This danger can be substantial when vacuum fil-... 

It is good to realize that the problem domains as defined above are generally characterized by a great complexity with regard to the composition of the samples. Moreover, very often the samples will contain not only dissolved material but also solid particles may be present with inherent risks of clogging of the analyzing equipment, etc. Dissolved gas may also cause problems, especially when the sample is heated and gas-bubble formation may occur. These problems may require special precautions to be taken in combination with pTAS such as filtration and degassing of the solutions. However, there are many more aspects to be considered which can be better discussed for the various domains separately. 

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The compounds benzonitrile, p-methylbenzonitrile, /)-methoxybenzonitrile, p-trifluoromethyl-benzonitrile, /)-methoxycarbonylbenzonitrile, and triethoxysilane are commercial products and are degassed and stored under argon before use. Trimethylsilane was prepared according to a literature report [38]. The nitrile (9.8 mmol) and the hydrosilane (49 mmol) are added to the rhodium catalyst (0.1 mmol) contained in a Carius tube. When using trimethylsilane, the operation is performed at —20°C. The tube is closed and the mixture stirred at 100 °C for 15h. The liquid is separated by filtration and the excess of hydrosilane removed under vacuum to leave the N, Wdisilylamine derivative. If necessary, a bulb to bulb distillation is performed to obtain a completely colorless liquid. The yields obtained in the different runs are reported in Table 6. The product have been characterized by elemental analysis, NMR spectroscopy, and GC-MS analysis. 

Left, Charlie Focht of the Nebraska State Agriculture Laboratory prepares the mobile phase for an atrazine assay. Note that the vacuum flask is positioned in an ultrasonic cleaner bath. Simultaneous vacuum filtration and sonication provide a more efficient means for degassing. Right, Charlie adjusts the flow rate setting on the HPLC pump. 

In this process, a vacuum extrusion step (melt treatment) is followed by a continuous SSP (solid treatment). The process starts with PET flakes which are introduced without pre-drying into a ring extruder. The flakes are dried, melted and degassed inside the extruder. A gear pump builds the necessary pressure for melt filtration, where solid particles are removed. After granulation the pellets are fed to a continuous three-step SSP unit [10]. 

The polymer-supported hydridoiron tetracarbonyl (33 mmol) is prepared by the addition ofFe(CO)5(6.46g, 33 mmol) to KOH (5.6 g, 0.1 mol) in aqueous EtOH (1 1 v/v, 100 ml) under N2. The mixture is heated with stirring under reflux for 2 h and Amberlyst A-26 resin (24 g) is then added and the mixture is stirred for a further 15 min. The resin is collected, washed with degassed H20 (to neutrality), MeOH and Et20, dried at room temperature under a flow of N2, and used immediately. The haloalkane (11 mmol) in THF (50 ml) is added to the resin and the mixture is stirred under reflux for ca. 4 h. When GLC analysis shows the reaction to be complete, the resin is removed by filtration, and the filtrate evaporated under reduced pressure to give the aliphatic aldehyde. 

Fort he determination of preservatives and sweeteners in soft drinks or fruit juices LC analysis with UV detection is widely used. The sample pretreatment, prior to LC analysis, often consists only of degassing, filtration and dilution of the Uqirid [2]. Sometimes a Uqirid-Uqitid extraction, suitable not only for soft drinks but also for more complex matrices, is appUed [3]. Chemometric methods appUed to overlapped spectra offer the advantage of minimizing or eliminating sample preparation by allowing to simirltaneoirsly determining one or more analytes in relatively complex matrices. 

G.L Eskin, Degassing, filtration, and grain refinement processes of light alloys in a field of acoustic cavitation. Advances in Sonochemistry, T.J. Mason (ed.), JAI Press, London, 1996, 4, 101-159. 

A degassed solution of potassium hydroxide (570 mg 9.62 mmol) in freshly distilled methanol (8mL) is prepared under nitrogen in a 50 mL round-bottomed flask equipped with a magnetic stirring bar. Solid Os6(CO)18 (150 mg 0.09 mmol) is added and the mixture is stirred at room temperature for 30 min. After addition of [PPN]C1 (Ventron) (330 mg, 0.57 mmol), the solution is cooled to — 25 °C for l6h. A brown powder is formed that is removed by filtration and washed with ice-cold methanol (10 mL). Yield 190 mg (85%). The compound does not need to be purified further. 

For the Al-modification of the PCH, 0.5g is degassed overnight at 200°C before reaction with Al(acac)3 during 1 hour at room temperature in toluene. The concentration of the complex is respectively 25%, 50%, 75%, 100%, 150% and 200% of the silanol concentration of the PCH. After reaction, the mixture has been filtrated and washed with fresh toluene. To remove excess of toluene, the Al-modified PCH is degassed during 4 hours at room temperature. To convert the adsorbed Al(acac)3 into aluminium oxide, a temperature treatment at 550°C during 16 hours (heating rate 2°C/min) was performed. 

Fluxing and degassing methods, combined with filtration, to give highest quality aircraft and other critical alloys. 

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