Biomedical Engineering Reference
In-Depth Information
as the working electrode. This carbon rod is drilled longitudinally so that the fluid passes
through the rod onto the carbon particles, which have been distributed evenly onto the
filter by centrifugation. Another hollow carbon rod acts as the counter electrode and a
hollow Ag/AgCl rod acts as the reference electrode as shown in Figure 22.4. The design is
engineered so that the fluid flows from the inlet of the immunosensor through the hollow
carbon rod onto the carbon particles on the filter and through the filter, and passes through
the hole in the hollow Ag/AgCl to the hole in the hollow carbon rod and then through the
outlet of the immunosensor. The design of the simple system is shown in Figure 22.5a. The
cross-sectional view is given in Figure 22.5b.
22.4.1
Field Test of Hemolysis Blood Samples
Since the introduction of quantitative determinations in clinical chemistry, hemolysis has
been recognized as an interference factor leading to increased levels of substances in
serum (plasma). Hemolysis is a well-known interferent in many assays [18
22].
Hemolysis is common in blood specimens, which occurs when blood contacts foreign
surfaces [22].
Hemolysis of samples is often encountered in clinical biochemistry. It results in a rosy to
bright red appearance of the plasma after centrifugation or sedimentation of red blood cells
and platelets. Hemolysis reflects the destruction of erythrocytes with release of hemoglobin
into the plasma, giving the red color. It is a source of error in electrolytic and enzymatic
Pump
Analyte
containing sample
W
R
C
Sampler
Flow
controller
Waste
FIGURE 22.4
Schematic flow-through automated immunofiltration system.
