Vacuum centrifuges

The use of centrifuges for isotope enrichment was suggested by Lindemann and Aston as early as 1919, but success required the development of vacuum centrifuges in the late 1930s. The rotors in such devices are suspended in vacuum chambers and gas is introduced and withdrawn through metal capillaries. Introductory discussions have been given by London (1961) and Benedict et al. (1981). 

Pre-concentration by vacuum centrifugation is a common technique used in many versions of current in-gel digestion methods and pHPLC. Throughout the process, the sample is exposed to many surfaces, which may contain a minimal number of active sites where losses can occur. The amount of sample loss may be negligible for concentrated samples, but loses at lower peptide concentrations, such as the femtomole (fm=10 M) level (see Table 3.1), increase markedly. ... 

Fractions are analyzed by MS or subjected to in vitro assays. For MS analysis, the collected fractions can be directly analyzed following dilution in the appropriate solvent. For activity screening, fractions are dried in a vacuum-centrifuge, reconstituted either in water or in a suitable buffer adapted to the activity monitoring. 

M4, 22 amines), and after the reaction the cleavage solutions were recovered by filtration into 96 corresponding microtiter plates to give crude L3 as 8448 spatially separated crude benzopyrans that were submitted to an automated purification procedure (step f) (115) and concentrated using commercially available vacuum centrifuges to give the final pure library (Fig. 6.15). 

About 10% of the sample was concentrated in a vacuum centrifuge to give an estimated concentration of 1 pmol/pl if possible. Samples were not dried down completely to avoid sample loss. The MALDI matrix was a saturated solution of a-cyano-4-hydroxy cinnamic acid dissolved in water/acetonitrile (7 3) [8]. A 0.5-pl aliquot of the matrix solution was placed on the stainless steel probe and mixed with an equal volume of sample solution. The mixture was left to dry at room temperature prior to introduction into the mass spectrometer. A new sample preparation method which decouples matrix surface preparation and sample handling was also used [9]. 

After creating positive pressure at the bottom, a cleavage reagent is dehvered to the top plate, which contains all the resins with the synthesized peptides. Upon completion of the cleavage, a vacuum is applied and the filtrates are collected in the 96 deep well collection plate at the bottom. The collection plate is then placed in a vacuum centrifuge to eliminate the cleavage mixture. 

Conversion of the ATZ-amino acids (extracted with TFA) to the PTH form was carried out off-line. After cleavage, the extract from each Edman degradation cycle was collected into a 2(X)-pL vial, to which 25 lL of 25% aqueous TFA solution was added and mixed. The solution was heated at 67°C for 10 min. and then dried on a vacuum centrifuge. The residue in the vial was dissolved in 1 pL... 

Accelab offers a complete fully automated high-throughput synthesis laboratory (Fig. 7), which includes synthesizer, solid-phase extraction module, balance, vor-texer, liquid-liquid extractor, and a vacuum centrifuge. A robot arm is in charge of all vessel transfers. 

Special features/comments complete high-throughput organic chemistry stand with synthesizer, SPE, balance, vortexer, liquid-liquid extraction module, vacuum centrifuge cooling with cold nitrogen gas multichannel (up to 8) pipette for solvent delivery reactive gas chemistry possible (rv can be pressurized up to 6 bar) 16 independent heating zones analytical port for in-line analysis (optional) on-board liquid-liquid extraction... 

For high-throughput evaporation, vacuum centrifuges are currently the devices that are in most tvidespread use. Equipment using orbital shaking as an alternative has also become available from several vendors. 

Gentrifuge rotors are available for a large variety of vessels and can in most cases also be made according to the customers specifications. Special swing-out rotors permit evaporation directly from (deep-well) microtiter plates or from vials held in racks with a microtiter plate footprint. Vacuum centrifuges are offered in various sizes, up to machines that can handle 12 or more deep-well microplates (Table 7). 

Cultures in the stationary phase were harvested by centrifugation at 10,000 g for 10 min. Aliquots of 1.2 ml were washed with different concentrations of sucrose and trehalose. After this, they were dehydrated for 30 min in a vacuum centrifuge (Integrated Speed Back System ISS 100 (Savant Knowledge Storm, Inc. 2520 Northwinds Parkway Suite 300 Alpharetta, GA 30004) at 70°C. Then they were immediately resuspended in distilled... 

Evaporate in heated, vacuumed centrifuge (Savant SpeedVac AE2000) for 25 min... 

Sample clean-up can be done rapidly using a short LC column operated under gravity flow or under vacuum, centrifuge or syringe pressure. The most popular phases include silica and bonded phases. Disposable and inexpensive columns are available and can be found under the following trade names Sample Enrichment and Purification, PreSep Extraction, Bond-Elute, and solid-phase extraction. For example, purification of sulfamethazine in milk by SPE followed by quantitative analysis by TLC has been described earher... 

Remove supernatant and dry the pellet briefly in a vacuum centrifuge. 

Care should be taken to ensure that the material is fully resuspended. If, for example, the sample is dried for several hours in a heated vacuum centrifuge, it may settle on the bottom of a tube as a hard crust that may be very difficult to fully resuspend. There is also a danger of a soluble compound appearing to be insoluble because it is physically associated with insoluble material and not properly accessible to the solvent In this case, ultrasonication, or mechanical mixing of samples is useful... 

The component of interest must finally be isolated from a small volume of organic solvent or solvent/water mix to yield the requisite pure product. This can be achieved by rotary evaporation, freeze-drying, or vacuum centrifugation. The choice of method depends on the equipment available, the amount of product isolated, and the purpose for which it is intended. These techniques are discussed further in Chapter 9. 

Sample preparation 0.5 mL Plasma or synovial fluid + 50 p,L 24 p.g/mL flurbiprofen + 200 jjiL 2 M HCl + 5 mL hexane, tumble 10 min on a rotary mixer, centrifuge at 10 000 g for 5 min. Remove organic layer and evaporate it to dryness under vacuum centrifugation. Reconstitute residue in 150 p-L MeOH -t- 100 p,L water, vortex mix, inject aliquot. 

Sample preparation Prewash a 1 mL CIS Bondelut CIS SPE cartridge with 3 mL MeCN and 3 mL water. 1 mL Serum or urine -(- 0.25 mL (0.50 mL for urine) 6-12 p,g/mL oleandomycin phosphate in water, add 1 mL MeCN, vortex 1 min, centrifuge at 1600 g for 5 min, add to 8 mL water, load onto the SPE cartridge, wash with 5 mL water, wash with 5 mL MeCN. water 1 1, suck dry, elute with two 0.5 mL aliquots of MeCN 50 mM pH 6.30 phosphate buffer. Diy under vacuum in a rotary vacuum centrifuge, reconstitute in 20 p,L water, vortex 1 min, add 25 p,L MeCN, vortex 1 min, centrifuge at 1600 g for 1 min, inject 3-5 pL aliquot of upper layer. 

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