BUCHI SpeedExtractor E-916 - Manual (Page 26)

4 Description of function
26 SpeedExtractor E-916/E-914 Operation Manual, Version D
cells is absolutely mandatory. Placing the cells in the cold instrument followed by heating up the
closed system might damage the cup seals. It is therefore crucial to note that the temperature of the
instrument must not be changed once the system is closed. The instrument is ready once the set
temperature is reached (which is shown in the main display) and the extraction process is started by
pressing START. In order to achieve reproducible results, it is recommended that the same proce-
dure always be followed. As the time used to reach the set temperature is depending on the absolute
set temperature, it is suggested that the extraction cells never be placed in the heating block until the
instrument is ready and to start the extraction process right away. This procedure guarantees that
the sample is not unnecessarily exposed to the hot environment and that this time period before the
actual process starts does not significantly influence the recovery of the extraction process.
In addition, placing extraction cells in all positions is highly recommended even though not all posi-
tions are used. This improves the heat uniformity of the heating block. It is possible to deactivate the
positions with the empty cells to avoid needless solvent consumption.
4.4 Schematic representation of the process
The following illustration provides a schematic representation of the pathways of the different media
for the E-916. Up to four different solvents a and nitrogen b are connected to the E-916. A media
valve f switches between solvent and nitrogen. The mixer d mixes the solvents that are selected
with the help of the solvent valves c.
The pump e transfers the solvent mixture to divider g where it is equally distributed to each of the
activated positions. Once the system is sealed by closing the extraction cells l with the upper and
lower tightening device that holds the cup seals k and m, the outlet valve o is closed in order to
increase the pressure inside the system. The pressure of each position is displayed by the pressure
sensors j. When the set pressure is reached (at the end of the heat-up step) the position valves i
are permanently closed, and the sample is extracted (hold step). In the discharge step the outlet
valve o opens, the hot mixture is cooled down by the cooling units n and finally transferred to the
collection vials p. Pressure compensation is achieved by the lines to the exhaust q. In case of an
overpressure, the outlet valve opens and releases solvent into the collection vials. Residual solvent
is optionally flushed with fresh solvent. An additional thorough flushing step with nitrogen removes
residual solvent in the lines. In addition, another optional flushing with solvent into waste instead of the
collection vials is possible by setting the outlet valve to waste r. This is usually done to prepare the
system for another run with a different solvent. For a thorough description of each step please refer to
section 6.4.