standards or reference solutions, it is usually best to average
the readings from three to five aliquots of each sample to avoid
error.
If you are running the instrument for the first time, it is recom-
mended that you follow the Lactrol
®
530 reference solution sam-
ples with bracketing calibration standards to check the instru-
ment accuracy and linearity over the range of interest.
6. Using the same techniques, unknown samples may be loaded
into any remaining cassette positions if desired.
7. Place the first cassette in the left (input) deck, with the labels
facing you.
8. Press START. The 4C3 will position the cassette, wipe the
probe and stir wire between the probe wipers, pick up the first
sample tube, place it in the sample freezing chamber, and per-
form the freezing point test.
The sample temperature will be displayed as soon as it falls
below 0°C. The 4C3 will freeze the sample at a fixed crystal-
lization point, follow the plateau development, determine the
freezing point as defined by the plateau mode selected (see
Chapter 1, Section K), and display and record the results. After
completing the test, the 4C3 will return the first sample tube to
the cassette, wipe the probe and return to the cassette for the
second tube. Figure 9 shows the operating head either loading or
unloading the third sample tube from a cassette.
The 4C3 will automatically index and test each of the remaining
samples in the cassette in turn, then it will position and test any
other cassettes in the batch which are placed in the input deck.
NOTE If the STOP button is pressed while testing is in progress,
the current test will be discontinued and the 4C3 will dis-
play “Press Start to Continue, Stop to Quit”. If
STOP is pressed the second time, testing will be terminated
and “Cryoscope Ready” will be displayed.
If testing is stopped during a barcoded test batch, either inten-
tionally or through some mechanical fault, any untested samples
must be re-scanned.
35
Instrument Operation
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