Advanced Instruments 4250, User Manual

Page: 45 / 121

reference solution and standards.
13. Always wipe the probe, stir/freeze wire, mandrel, and the top of the
freezing chamber with a soft, clean, dry, lint-free paper tissue after
the last test, to avoid having contaminating material dry on the
probe.
14. Leave an empty sample tube in the freezing chamber to help avoid
having to clean out accidentally-introduced material.
Sample test procedure
Instrument operation in the following manner is recommended:
1. Remove the sample tube from the freezing chamber (see Figure 5,
Item 8).
2. Gently wipe the probe, stir/freeze wire, mandrel, and the top of the
freezing chamber (in that order) with a soft, lint-free, non-ionic paper
tissue dampened with distilled water to remove anything that might
contaminate the sample to be tested. Be careful not to bend the probe
or stir/freeze wire.
3. Select a reference solution or NaCl standard with a freezing point
close to that expected for your unknown (Advanced Lactrol® 530
Reference Solution is recommended for milk). Swirl and carefully
open an ampule of the reference solution (or NaCl standard selected).
4. Pipette or measure a sample into the clean sample tube and place the
tube in the freezing chamber (see page 20, Repeatability Tips).
5. Press the START soft key.
6. If “ I.D. # ” has been enabled, the instrument operator will be prompt-
ed for a sample or user identification number of up to 13 digits at
this time. A new number may be entered via the optional barcode
scanner or one digit at a time from the left via the numeric keypad.
Press ENTER . “ Press Start to Continue ,” will begin to scroll
across the display. Press START .
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Instrument Operation