Centrifugation vacuum concentration

Compare the techniques of lyophilization and centrifugal vacuum concentration. Give advantages and disadvantages of each. 

The SpeedVac centrifugal vacuum concentrator Courtesy of Savant Instruments (savantec savec com)... 

Dry the gel pieces completely in a centrifugal vacuum concentrator. Caution should be exercised in handling the dried gel pieces, as they are easily lost from tubes or plates. 

Centrifugal vacuum concentrator (SAVANT SPD 111 V SpeedVac Concentrator, Thermo Electron Corporation). 

For precipitation of DNA and RNA, add 10% of the volume sodium acetate, pH 7 or 5.2, respectively. Add four parts of ice-cold 98% ethanol and mix well. Add 1 pi of linear acrylamide (3%). Incubate for 2 h at -20°C and centrifuge at 12,000 for 30 min in a tabletop centrifuge. Carefully remove the supernatant—the DNA or RNA should be visible against the light as one or several small shiny specks, usually attached to the tube, but they may be loose—and wash the pellet with 200 pi 80% ethanol. Remove the supernatant, and dry the DNA or RNA (3 min in a speed vacuum concentrator) until all visible liquid has gone, but avoid overdrying of the pellet because the DNA or RNA will then be difficult to redissolve. Dissolve the DNA in 100 pi dd H O. 

Production of lactose essentially involves concentrating whey or ultrafiltration permeate by vacuum concentration, crystallization of lactose from the concentrate, recovery of the crystals by centrifugation and drying of the crystals (Figure 2.15). The first-crop crystals are usually contaminated with riboflavin and are therefore yellowish a higher grade, and hence more... 

An oven-dried reaction vial was charged with 0.100 g of nucleoside (0.171 mmol), 0.078 g of cesium carbonate (0.24 mmol, 1.4 equiv), 0.004 g of palladium acetate (0.017 mmol, 0.1 equiv), 0.016 g of BINAP (0.025 mmol, 0.15 equiv), 0.22 mmol of aryl bromide (1.3 equiv), and 1 mL of toluene. The vial was flushed with argon prior to sealing. The reaction mixture was stirred for 30 min at room temperature, heated at 80°C for 16 h, and then diluted with ethyl acetate. Centrifugation and concentration in a vacuum of the supernant liquid afforded a residue, which was purified by flash chromatography (silica gel, 10-30% ethyl acetate in hexane) to afford 0.116 g of A -(2-nitrophenyl)-(7 -benzyl-3, 5 -bis-0-( r -butyldimethylsilyl)-2 -deoxyguanosine as a yellow amorphous solid, in yield of 96%. 

Although there are several ways in which solid/liquid separation may be achieved (e.g. settling, flotation, hydrocyclones, evaporation, magnetic, electrostatic, gravity, centrifuge, vacuum, and pressure), the mechanisms that consume the largest volume of textile filter media, and on which this section will concentrate, are those of pressure and vacuum. 

The water methanol extract is divided into 10-1. batches, and to each is added, with mixing, 15 ml. of 2 JV NaOH and 380 ml. of a solution of the following composition 450 g. lead acetate 150 g. lead oxide -f 2 1. of water. The precipitate is separated by centrifugation, washed, and the supernatant and wash water are pooled. This liquid is acidified by addition of 30 ml. of 2 N sulfuric acid per 10 1., then is vacuum concentrated to one-sixteenth of its volume. The excess lead is removed by addition of sulfuric acid and filtration. 

Concentration and Aroma Recovery. Concentration of juice from deciduous fmit is best carried out using an evaporator that causes as httle thermal degradation as possible and that permits recovery of volatile materials important to the aroma of the fresh fmit, ie, essence. Evaporators that use a high temperature for a short time and operate under a vacuum, such as the APV Crepaco falling film plate evaporator or the Alfa Laval centrifugal... 

The reaction takes place at atmospheric pressure. For stable control of the reaction rate, the reaction is first carried out at a temperature of 50°C and then at 60°C. Overall, this batch reaction takes about 9 hours. After completion of reaction, the slurry is diluted to about 70% sulfuric acid solution, and cmde sulfamic acid crystals are separated by centrifuge. The crystals are dissolved in mother Hquor to make a saturated solution at 60°C and the solution is concentrated under vacuum at 40°C. Purified sulfamic acid is obtained by recrystallization. 

The cmde oxide is pressure-leached in a steam-heated autoclave using water or circulating mother hquor. The arsenic trioxide dissolves, leaving behind a residue containing a high concentration of heavy metal impurities and sihca. The solution is vacuum-cooled and the crystallisation is controUed so that a coarse oxide is obtained which is removed by centrifuging. The mother hquor is recycled. The oxide (at least 99% purity) is dried and packaged in a closed system. 

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