If premature crystallization is occurring because of congealed liq-
uids in the sample, the problem may be alleviated by pre-warming
the samples to 40°C for five minutes but note that, for calibration
accuracy, the standards should be pre-warmed as well.
Particulate matter can also cause premature crystallization. Both
particulate matter and congealed liquids may be removed by filtra-
tion through an inert filter, or by centrifugation of the sample.
D. Sample test procedure
If the 4C3 has been turned off, it should be started as indicated in
Chapter 1.
Like most measuring instruments, cryoscopes need calibration
against standards. Your 4C3 was calibrated at -408 m°C and -600
m°C at the factory using the procedure described in Chapter 4. The
probe and calibration parameters are stored in parameter RAM,
which is powered by an internal battery when the instrument power
is off or disconnected. Thus, when “Cryoscope Ready” is dis-
played, your 4C3 is calibrated and ready to run. However, the cal-
ibration should always be verified during operation to be sure that
none of the parameters affecting calibration have changed. In the
recommended procedure which follows, calibration verification is
accomplished by starting with the Lactrol
®
530 reference solution.
Then, if recalibration is indicated, see Chapter 4.
If either batch numbering or barcode scanning has been enabled,
follow the procedure in section E before returning to the following
steps. If neither batch numbering nor barcode scanning has been
enabled via the setup menu, instrument operation in the following
manner is recommended:
1. Check the probe wipers (see figure 5). Replace the wiper spong-
es when they begin to appear dirty, or about every 50 tests.
Check the drip catcher (see figure 5). Replace the drip catcher
sponge when it appears dirty, ineffective or shows excessive
wear.
33
Instrument Operation
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