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Instrument Operation
Glass tubes generally are not as uniform in shape and size as plastic
tubes, nor do they thermally isolate test samples as well. The 3250
operating parameters are optimized for Advanced Instruments plastic
sample tubes (Part No. 3LA825); glass sample tubes may not provide
the same repeatability. If you need further information concerning
sample tube requirements, please contact Advanced Instruments as
recommended in Chapter 5.
Samples should always be pipetted or measured. 0.25-mL or 0.2-mL
samples may be used in Advanced Instruments sample tubes. To
achieve the specified performance, we recommend that you use 0.25-
mL samples; 0.2-mL samples require somewhat more critical probe and
stir/freeze wire adjustments for similar precision in results. The 3250
should be calibrated with the same sample size used for testing.
Verifying calibration daily
Like most measuring instruments, osmometers need calibration against
standards. Your 3250 was calibrated at the factory using the optional
Zero calibrator. The probe and calibration parameters are stored in
parameter RAM which is powered by an internal battery when the
instrument power is off or disconnected. Thus, when Osmometer Ready
is displayed, your 3250 osmometer is calibrated and ready to run.
However, the calibration should always be verified during operation to
be sure that none of the parameters affecting calibration have changed.
(If recalibration is required, see Chapter 4).
Note To verify the precision of your instrument, test products with
known values within your reportable range (i.e., Clinitrol
™
290
mOsm/kg, Protinol
™
Protein-based Controls, Renol
™
Urine
Osmolality Controls).
Following is the recommended procedure for instrument operation:
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