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The Advanced
®
Osmometer Model 3900 User’s Guide
Repeatability Tips
• Gently wipe the mandrel, probe and stir/freeze wire with a pure water
dampened tis sue to remove any contaminant’s before each set of tests,
after about every 50 tests, and after each set of tests. Be careful not
to bend the probe or stir/freeze wire.
• Sample tube cleanliness is extremely important for repeatability. New
Advanced plastic sample tubes may be expected to be clean. If glass
tubes are required, they should be washed in hot water con taining a
non-ionic detergent, rinsed in distilled water, and thoroughly dried
before each use.
• Always treat all samples uniformly before the test. Treat standards
and reference solutions the same as the unknowns. Do not intermix
different tube styles.
• To avoid contamination and evaporation, cover all samples not imme-
diately being tested.
• Dirty wipers can affect the results. Replace the probe wipers when
they begin to appear dirty (about every 50 tests).
• Use the same sample size consistently during calibration and testing.
• Samples should not be rerun; use duplicate samples for repeats.
• The first reading in any given period of operation may be slightly off
because of temperature con ditioning or residual contamination of the
probe. Subsequent readings on aliquots of the same sam ple should
group within the specifications listed in Appendix B.
• If an occasional sample produces irregular results, discard obviously
discrepant readings as long as the instrument has been producing
accurate read ings repeatedly. Repeat the reading in question on
another aliquot.
• To reduce the effects of evaporation, use the evaporation kit provided
in the accessory kit. Refer to the instructions on the cover for instal-
lation.