20
Advanced
®
Cryoscope Model 4250 User’s Guide
Repeatability Tips
1. Sample tube cleanliness is extremely important for repeatabili-
ty. Glass tubes should be washed in hot water containing a non-
ionic detergent, rinsed in distilled water, and thoroughly dried
before each use.
2. Always treat all samples uniformly before the test. Treat stan-
dards and reference solutions the same as the unknowns. Do not
intermix different tube styles.
3. To avoid contamination and evaporation, cover all samples not
immediately being tested.
4. Use the same sample size consistently (i.e., during calibration,
testing, etc.).
5. For repeat runs, use another sample from the same source or
thaw the original sample before repeating. If you must rerun the
same sample or use it for another procedure, remove it from the
freezing chamber as soon as possible and keep it covered
between tests.
6. Always use the same operating procedure as proper, consistent
procedure is the key to repeatable results.
7. The first reading in any given period of operation may be slight-
ly off because of temperature conditioning or residual contami-
nation of the probe. Subsequent readings on aliquots of the same
sample should group within the specifications as in Appendix B,
if you practice good operating techniques.
8. If an occasional sample produces irregular results, discard obvi-
ously discrepant readings as long as the instrument has been
producing accurate readings repeatedly. Repeat the reading in
question.
NOTE Proper instrument operation and warranty protection is
dependent upon the use of Advanced Instruments supplies,
parts and accessories, noted on pages xi-xiii.
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