1.2 Processing
The Stomacher® 80 Biomaster is factory-set with minimal paddle clearance
between the inner face of the door and the fully extended paddles. Although
suited to a wide range of applications these settings are by no means suitable for
all sample processing and adjustment may be necessary for your application.
Provision for this adjustment is provided inside the instrument. Since this requires
the removal of the rear cover a competent qualified technician should carry out
this work.
1.3 Paddle Adjustment
Switch off and disconnect the instrument from the mains electrical supply. Turn
the instrument over, suitably supporting it to prevent damage. Remove the rear
cover and slacken the socket cap screws holding the motor carriage to the main
body via the slotted holes. Do not slacken any of the screws within the carriage
assembly or the motor alignment will be lost. Remove the large hexagon headed
blanking plug (if fitted) from the rear chassis to access the adjusting screw. Turn
the adjusting screw until each paddle just touches the inside face of the door
when they are at their maximum forward stroke position, this can be tested by
manually rotating the gearbox output shaft.
If the instrument is run briefly the alternate tapping noise of each paddle touching
the door should just be audible. Take up any backlash in the adjusting screw and
turn the screw back one to one and a quarter turns.
This is the minimum clearance setting.
For a greater paddle clearance, each additional backward turn of the adjusting
screw increases the clearance by 1.5mm up to a maximum of 10mm.
When adjustment is complete always re-tighten the socket cap screws, replace
the hexagon headed blanking plug where fitted, and replace the rear cover.
1.4 After Processing
Due to the infinite variety of samples that may be processed in a Stomacher® it
is not possible to provide definitive procedures for every application, or give any
undertaking, implied or otherwise, as to the validity of any method used. Seward
Limited maintain a library of reference papers covering practical experience with
the Stomacher® system over many years and these details are available to users
upon request.
2. APPLICATION
There are no set rules in the application of the Stomacher® instrument and the
following is intended as a guide only and not to restrict laboratory technique.
2.1 Bag Selection and Filling
For best results it is recommended that only genuine Seward Stomacher® Bags
be used. Deep frozen foods should not harm the bags but hard particles such
as bone, grit, fruit-stones and seeds may cause puncturing. Where a marginal
condition exists or any hazardous material is being blended it is recommended
that two bags are used one inside the other.
If required, several bags may be processed simultaneously providing the total
volume does not exceed 80 ml. When doing so, it is recommended that they be
layered vertically so that the ‘load’ is fairly evenly distributed over the paddle
faces.
For volumes greater than 80ml, an alternative Stomacher® model should be used.
2.2 Speed Selection
The NORM. (normal) speed is suitable for the vast majority of applications and the
instrument will always set automatically to that position upon powering up. If an
alternative speed setting is desired this may be selected either prior to or during
operation of the instrument. When depressed a short signal will be heard and the
corresponding small indicator lamp at the top corner of the touch pad will
illuminate.
The LOW speed may be more suitable for delicate work e.g. cell separation
to reduce or avoid cell damage. Use of the HIGH speed can provide better
agitation when blending predominantly liquid substances possibly reducing the
processing time. In the event of the power being interrupted the speedsetting will
always revert to NORM.
2.3 Control Key Functions
The touch control panel, located on top of the Stomacher®, has the following
functions:
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