Sample holders: the right tool for the job

Solvent evaporation is used for a wide range of applications with many different solutes, solvents and containers. Using the right sample holder for your container type is important to ensure operating efficiency and to prevent product waste

Samples in racks loaded in a centrifugal evaporator

Solvent evaporation is used for an incredibly wide range of applications with many different solutes, solvents and containers. Using the right sample holder for your container type is important to ensure operating efficiency and to prevent product waste.

A major factor in determining the speed of evaporation is the rate at which heat enters the sample. As well as the temperature of the heat lamps or thermal medium, the thermal conductivity of any materials in between must also be taken into consideration. This includes the container itself and the plates or racks holding the samples.

Materials such as glass and plastic do not transfer heat energy well and will act as insulators to prevent the sample being effectively warmed. For best results, sample holders should be manufactured from solid metal. Aluminium is ideal: as well as being a good heat conductor, it is lightweight.

Evaporate up to 3.5 times faster

It might seem this adjustment would not make a significant difference. However, the difference in runtime between a 'real' Gilson rack and Genevac’s 'modified rack' was dramatic: 15 hours compared with just four hours. The Genevac approach is more than 3.5 times faster.

Genevac’s 'modified racks' are completely compatible with the relevant fraction collection system but also optimised as an evaporator sample holder. This also means no manually moving tubes from one rack to another after fraction collection.

Heat transfer plates

Genevac’s heat transfer plates provide improved evaporation results when using microtitre plates, by improving the flow of heat to the product. Improvements will be seen in the evenness of sample drying across the plate and, for some applications, they may help to reduce evaporation times by up to 50%.

Genevac’s heat transfer plate ensures maximum heat transfer to the sample itself

Precise fit

Sample holders should be designed to match the container type as tightly as possible. Firstly, this helps with heat transfer as any air pockets or spaces would slow down the heat transfer. Secondly a precise fit will help prevent breakages.

For added protection against glassware breakage, some sample holders must be used with thermal cushions. Thermal cushions are made from a filled polymer with excellent heat transfer and cushioning properties.

Concentrating large volumes directly into small vials

Many laboratories are familiar with the problem of significant sample loss when concentrating large volume samples and transferring the residue into a dedicated analysis support or storage format, such as a vial. The SampleGenie comprises a specially designed glass funnel/flask that securely seals to a storage vial, dramatically increasing its capacity, allowing a large volume sample to be evaporated directly into the sample vial and eliminating the transfer step.

SampleGenie is particularly beneficial for applications such as medicinal chemistry, metabolism and environmental analysis.

SampleGenie allows concentration of a large volume of sample directly into the final vial or bottle

A word about glass

Glass can be a highly variable product. Not all types of glassware can reliably be used in a Genevac solvent evaporator, due to the fragility of the material, frequency of defects, shape of the container or variation in dimensions that is difficult to accommodate in a standard sample holder.

Handmade or hand-blown glassware tends to have more variation, but even mass-produced machine-made glass cannot be produced to precise dimensions, particularly own-brand catalogue stock. Genevac can evaluate any glassware to ensure it is suitable for centrifugal evaporation.

Standard and non-standard sample holders

As the market leader in centrifugal evaporation, Genevac has already designed holders for the majority of applications. Standard sample holders are available for containers such as:

  • Microtitre plates
  • Radleys Carousel Tubes
  • Dionex ASE tubes
  • Round-bottomed flasks
  • GC auto-sampler vials
  • HPLC vials
  • Scintillation vials
  • Centrifuge and microcentrifuge tubes

Should you find your application or tube size is not already covered, a special holder can be designed.

Featured Companies

Biopharma Group (more information, website)

See also