APPENDIX
D
Special Application Notes
Clinical and General Research
The Vapro osmometer has unique advantages in many aspects of clini-
cal chemistry due to its very small sample requirement. This is particu-
larly true in pediatric practice. For example, the amount of sample col-
lected for sweat, fecal, sputum, duodenal, and gastric analysis is fre-
quently too small to allow osmolality assay by older macro methods,
especially since other analytical parameters are very often simultane-
ously requested on such specimens.
An equally important advantage is that the vapor pressure osmometer
does not physically change the sample. Where biological specimens or
medications are multiphasic, or highly viscous, vapor pressure osmome-
try becomes the only reliable method of measurement. For example,
feces, sputum, and gastrointestinal aspirate specimens usually contain
variable amounts of mucous material that interferes with or prevents
freezing point depression measurements but does not affect vapor pres-
sure osmometry. Neither does the presence of finely suspended insolu-
ble material, a feature of radio-opaque media, which are often examined
to detect grossly high osmolality values likely to produce rapid dehydra-
tion when given to small infants.
In general research, the potential applications are too numerous to list.
However, the vapor pressure osmometer is of value to a wide range of
biologists and microbiologists concerned with fluid and electrolyte bal-
ance in all forms of life, especially where specimens are necessarily very
limited in size, and may exhibit unusual viscosity.
The instrument is capable of vapor pressure determinations
(expressed as osmolality) even on complex specimens such as tis-
sue sections. Such specimens should be cut to approximately the
diameter and thickness of the paper sample disc, if possible.
For experimental purposes, large-volume sample holders are available.
These sample holders will accommodate gross specimens that are not
amenable to testing with the standard shallow sample holder.
Contact Wescor for more information.
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