OsmoPRO MAX Automated Osmometer User Guide
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1.1 Product Description and Purpose
Built for clinical laboratories of all sizes, the
OsmoPRO MAX delivers unprecedented ease-of-use and
efficiency. Innovative flow-through technology
revolutionizes osmolality testing by eliminating the need
for consumables.
With the OsmoPRO MAX, samples are automatically
pipetted directly from the primary tube and tested
within the device. Continuous loading and unloading
allows the user to begin testing as soon as samples come
in, removing the need to batch test.
1.2 Intended Use
Advanced Instruments Osmometers use the method of
freezing point depression to measure osmolality.
Osmolality is the total solute concentration of an
aqueous solution. Osmometers measure the number of
solute particles irrespective of molecular weight or ionic
charge.
The OsmoPRO MAX provides osmolality measurement of
serum, plasma, and urine, and is intended for use by
trained healthcare professionals. Osmolality is a valuable
clinical tool used in the diagnosis and treatment of
patients. It is a quick and effective test to help evaluate
the body’s water balance or its ability to produce and
concentrate urine, to investigate low sodium levels
(hyponatremia), to detect the presence of toxins in the
body, and to monitor the osmolality of patients
undergoing osmotically active drug therapies such as
mannitol, which is used to treat cerebral edema.
This test is also ordered to help monitor the effectiveness
of a treatment for a condition found to be adversely
affecting a person’s osmolality.
Operation of the instrument is deemed moderately
complex under CLIA and FDA guidelines.
Refer to
Configuring Instrument Settings
for instructions
on using any of the data management features
mentioned in this chapter.
1.3 Principles of Freezing-Point Osmometry
When a solute is dissolved in a pure solvent, the
following changes in the solution’s properties occur:
•
The freezing point is depressed
•
The boiling point is raised
•
The osmotic pressure increases
•
The vapor pressure decreases
These are the so-called
colligative
or concentrative
properties of the solution which, within reasonable limits,
change in direct proportion to the solute concentration
(the number of particles in solution).
Of the colligative properties, measuring the freezing
point allows for precisely determining the concentration
of an aqueous solution.
One mole of a non-dissociating solute (one that does not
dissociate into ionic species)—such as glucose dissolved
in 1 kg of water—depresses the freezing point of the
water by 1.858 °C. This change is known as the freezing
point depression constant for water.
The freezing point depression also depends on the
degree of dissociation of the solute. If the solute
dissociates, each species contributes to the freezing
point depression. For example, if one mole of sodium
chloride were to completely dissociate into one mole of
Na+ and one mole of Cl- in 1 kg of water, the freezing
point would be depressed by 3.716 °C. However,
dissociation is never complete. Interference between
solute molecules reduces dissociation by a factor called
the osmotic coefficient.
In a simple solution—for example, glucose or sodium
chloride in water—the freezing point can be measured
and the unit concentration easily determined from an
equation or a reference table. However, the equation is
unique for each solute. In a more complex solution, all
ionized and non-dissociated species contribute to the
freezing point depression. The concentration of each
solute cannot be easily determined.
Chapter 1:
OsmoPRO MAX Overview
