Advanced Instruments 4250, User Manual

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are calibrated with standards consisting of stable sodium chloride solu-
tions of known freezing points which bracket those of the expected
unknowns. These standards are related to the most fundamental work
on freezing points of dilute solutions published, and are traceable to the
National Institute of Standards and Technology (formerly the National
Bureau of Standards).
However, the most important cryoscope determinations are made, not
on sodium chloride, but on complex biological solutions. How accurate-
ly they determine the freezing points of precisely-known concentrations
of sodium chloride solutions, therefore, is only one measure of
cryoscope accuracy. Another measure should involve determinations on
solutions or controls formulated to synthesize the solutions to be tested.
Please check with your associations and regulatory bodies for their
guidelines and/or control requirements.
Maintenance of standards
Doubts about the accuracy of standards destroy confidence in the accu-
racy of the test. Advanced cryoscope standards are specified to be with-
in very close tolerances. Several of the sodium chloride based reference
and calibration solutions designed for the Advanced cryoscopes are
sealed in glass ampules to insure against any possibility of alteration
during transit or storage. However, we recommend that you test samples
from each newly-received lot and maintain records of your test results
on cryoscope standards for reference.
Quality control implementation
The following recommendations outline the minimum requirements for
quality control:
1. Read, understand and follow the instructions and recommendations
in the user's guide as closely as practical.
2. The instrument repeatability and accuracy should be checked each
time it is used, as recommended in step 11 of the sample test proce-
Advanced
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Cryoscope Model 4250 User’s Guide
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