Bayer HealthCare Rapidlab 800 - Manual (Page 641)

Operating Principles IĆ21
The loss of electrons in the oxidation of H
2
O
2
creates a current flow that is directly
proportional to the lactate concentration in the sample.
In the lactate sensor, lactic acid from the sample interacts with the lactate oxidase
on the surface of the measuring electrode to form pyruvic acid and hydrogen
peroxide
C
3
H
6
O
3
) H
2
O
) O
2
LOD
³ C
3
H
4
O
3
) H
2
O
2
(lactic acid) (pyruvic acid)
where LOD is the lactate oxidase.
The polarizing voltage is sufficient to cause oxidation of the hydrogen peroxide to
oxygen.
H
2
O
2
³ 2H ) ) O
2
) 2e –
The loss of electrons in the oxidation of H
2
O
2
creates a current flow that is directly
proportional to the lactate concentration in the sample.
Hemoglobin and its Derivatives
Hemoglobin analysis yields important information necessary to assess the function
of the oxygen transport system. The need for hemoglobin determinations has led to
the development of a number of methods to determine the concentration of total
hemoglobin, hemoglobin derivatives, and dyshemoglobins in whole blood. The
presence of dyshemoglobins and toxins changes the oxygen binding capacity of
hemoglobin and therefore its ability to transport oxygen.
33
Hemoglobin is a tetrameric protein consisting of two pairs of polypeptide chains,
each chain having a heme group containing one atom of iron. Each molecule of
hemoglobin can bind up to four molecules of oxygen, one at each heme group.
Hemoglobin has a key role in the transport of oxygen from the lungs to the tissues
and the transport of carbon dioxide from the tissues to the lungs.
Hemoglobin’s ability to bind and release oxygen depends on several factors: 37 pH,
pCO
2
, pO
2
, 2, 3–diphosphoglycerate concentration, temperature.
The presence of dyshemoglobins (that is, hemoglobins not available for reversible
binding with oxygen), such as carboxyhemoglobin, methemoglobin, and
sulfhemoglobin, as well as abnormal concentrations of hemoglobin variants, such
as fetal hemoglobin, may also affect the normal oxygen transport mechanism.
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