Extraction Unit B-811 Standard
 | Automated Extraction in Three Steps |
Extraction Methods
What is the difference between the four extraction methods offered by the B-811?
- Soxhlet Standard:
The sample is extracted in condensed solvent, which is regularly exchanged against fresh solvent. - Soxhlet Warm:
The sample is extracted in hot solvent, which is regularly exchanged against fresh solvent. This leads to faster extraction times compared to Soxhlet Standard. - Hot Extraction:
The sample is extracted in boiling solvent. The principle is comparable to extraction according to Randall or Twisselman. - Continuous Extraction:
The sample is rinsed with condensed solvent.
Ex-proof
Why doesn't BUCHI offer an ex-approved version of the B-811?
Ex-protection means to prevent the origin of explosions: sources of ignition and explosive mixtures.
- Sources of ignition:
Extraction Systems are used in labs, which are usually not ex-protected. Placing ex-protected devices into a room, where for example the light switch can generate sparks, is counterproductive. This means not only the device itself but also the surrounding has to fulfill special requirements to affect real ex-protection. - Explosive mixtures:
Typical ranges of solvent volumes for ex-protected areas are 5 to 10 l. With the B-811 less than 500 ml are used at the same time. If necessary, the presence of explosive gas mixtures can be minimized by performing the extraction in an inert gas atmosphere or at least those gas mixtures can be removed under a fume hood.
Fume hood
When is it recommended to work under a fume hood?
The B-811 offers under normal conditions (when the unit is adequately used and maintained in good condition) an excellent solvent recovery rate thanks to its high degree of tightness. This means that there is practically no loss of solvent vapors and that it is not necessary to work under a fume hood.
However, when the cooling water temperature is not cold enough or when working with health hazardous solvent, we recommend that for safety reasons, the unit is placed in a fume hood.
Inertness
What does "inert" mean?
In the B-811, the sample, the extract and the solvent only get in contact with inert materials glass, PTFE (sealing systems) and Fluorez (membrane in the glass valve).
Additionally the extraction and drying process can be performed in an inert gas atmosphere.
LSV
What is the use of the B-811 Large Sample Volume?
The basic idea of these glass parts is to offer our customer the possibility to work with larger amounts of sample (for sample preparation for example).
You can extract more sample (volume LSV glass sample tube 280ml) with more solvent (volume LSV solvent cup 230ml).
Program diversity
Is it possible to use different programs in different extraction positions simultaneously?
No, it is not possible to run different programs simultaneously. The set temperature and extraction times are the same for all four extraction positions.
Which heating level is recommended?
Application Note 811049en shows a list of common solvents and the recommended heating steps as well as the relationship of heating level, enthalpy of vaporization and boiling point.
Recirculating chiller
When is it recommended to work with a recirculating chiller?
The temperature difference between the boiling point of the solvent and the cooling water temperature should be 20-25°C in order to achieve a good condensation of the solvent in the condenser and to keep a good solvent recovery throughout the extraction. When using solvents like dichloromethane or petroleum ether, a recirculating chiller should be used if the tap water is warmer than 15°C.
Safety
Which safety features does the B-811 offer?
- Cooling water:
The extraction can?t be started without cooling water. If the water flow stops during the extraction the instrument is switched off automatically. - Tight system:
Solvent-resistent sealing materials and reliable workmanship produce a tight system. With two spirals per cooler the cooling efficiency is very high, minimizing loss of solvent through evaporation and therefore damage of human and environment. - Empty solvent cup:
A sensor in the heating plate recognizes an increase of temperature indicating that almost no solvent is left. The appropriate heating power is switched off automatically, the process of the other positions is not afftected. - IR Heating:
after switching off the heating plate is cold within seconds. - Protective shield:
The infrangible shield provides an extra precaution.
Sample tubes
What are the differences between glass thimbles and paper filters?
- Glass sample tube:
Consists of a glass tube closed with a glass frit (porosity of 1). The standard glass sample tube has a volume of approx. 120ml, the LSV version 280ml. They are reusable and may be cleaned in the dishwasher. The standard glass sample tube also fits into the Hydrolysis Unit B-411. - Paper thimble:
They are usually used once and then thrown away. BUCHI offers four different adapters for different sizes of paper thimbles (25x100, 22x100, 33x94, 43x123 mm).
