Is VariPrep for me?

We found a multitude of benefits beyond the initial design for MATRIX deposition via sublimation: While many laboratories replicate a publication about matrix deposition inside of a glass sublimator (in-house built setup), only few are financially able to obtain devices by mass spectrometer manufacturers.

 

There are clearly two main reasons to go to do MALDI sample preparation with VariPrep:

  1. No need for grant money.

  2. It does'nt need a hood.

How much does it cost?

The starter kit is available from 650€. We provide additional parts (pump, vacuum sensor, heater) up to the entire infrastructure for a sample preparation workplace for less than 10k€.

What can it be used for?

Sublimation of chemicals, like MALDI matrix deposition. Sublimation is also possible for derivatization agents like 4-APEBA.

You can use VariPrep for solvent vapor, so recrystallization is possible.

Desiccation, so a sample can be dried under vacuum. Additionally, a VariPrep fits a fridge or even freezer, so the sample does not need to dry at room temperature.
Due to VariPrep being cordless, one can transfer it into a glove box to work in inert gas atmosphere.
In the end, it is a small and lightweight container to move samples between different rooms and laboratories.
Core facilities can provide customers of their services with VariPrep to perform sample preparation sooner and preserve almost in-situ sample quality.

What do I need to make a VariPrep work in my lab?

For sublimation: A sub millibar vacuum pump (chemically resistant membrane pumps are NOT strong enough), and a flat surfaced heater like a magnetic stirrer.

For desiccation: A vacuum pump.

For recrystallization: The respective solvent.

 

Ask for free consultation to learn about the most cost efficient way to achieve more without additional grants!

 

Does VariPrep yield good results?

Yes. VariPrep crystal sizes outperform the spatial resolution of todays MALDI mass spectrometers with less than 1µm, e.g. for DHB. Integrating recrystallization enables high signal intensity.

How long does it last?

VariPrep consists of robust, shatter-free materials. Operated below 200°C, VariPrep does not encounter known defects. We do not know of any deterioration since its launch, durability is more than one year so far.

Which matrix chemicals are supported for sublimation with VariPrep?

Any (matrix) chemical that has been shown to sublime is supported. VariPrep is a vessel, the capability of a matrix chemical to sublime is inherent to it if the physical system provides the necessary temperature and pressure. VariPrep supports temperatures up to 200°C, while the pump provides the vacuum.

Matrix    Typical use                     Target density [mg/cm²]    Source amount [mg] sublimation time [min] Temperature [°C]
1,5-DAN   Lipids                                      ~0.05 - 0.2        ~2.2 - 9         TBD                    130°C
2,5-DHB   Lipids, metabolites, glycans                ~0.1 - 0.5         ~4.5 - 22        3:00                   140°C      
DHAP      Lipids, proteins                            ~0.05 - 0.2        ~2.2 - 9         3:00                   100°C
9AA       Metabolites, lipids                         ~0.05 - 0.2        ~2.2 - 9         TBD                    TBD
NEDC      Small metabolites, anions                   ~0.1 - 0.3         ~4.5 - 14        20:00                  160°C   
SA        Intact proteins                             ~0.2 - 0.5         ~9.0 - 22        TBD                    150°C
CHCA      Peptides, tryptic digests, small molecules  ~0.1 - 0.3         ~4.5 - 14        15:00                  160°C   

Here is a table of matrices which sublime below 200°C in sub-millibar vacuum (pmax < 0.1mbar). Times differ, cooling of the vessel top might be necessary after 5 minutes. Displayed amounts are calculated for 7.5cm * 2.5cm slides.

Sublimation workflow

Sublimation of MALDI matrices is performed in sub-millibar vacuum. Journal publications mention different matrices to be eligible for sublimation below 200°C. A detailed workflow with caveats is described in the user manual, generally it breaks down to these 5 steps:

  1. Prepare the VariPrep bottom with 1.25 times the amount of matrix you want to deposit on the target.
  2. Assemble the VariPrep with the target inside, so that the specimen faces the matrix powder at the distancer, and close it with the top lid.
  3. Evacuate the VariPrep with a suitable vacuum pump.
  4. Heat up the VariPrep on a magnetic stirrer or other regulated heat source for the needed sublimation time.
  5. Remove the VariPrep from the heat source and ventilate it to recover the prepared sample.

Recrystallization workflow

Solvent can be dispensed on the bottom lid of the VariPrep to provide solvent vapour. Usually performed in a petri dish, VariPrep allows for the reduction of solvent volume and therefore better control of the solvent saturation within the gas phase and smaller droplet size. The airtight design of the VariPrep enables oxygen-free preparation where needed. Details will be provided in a newer version of the user manual.