Description of the analyser
20.08.2012 Page 15 of 42 Rev. 04
Fig. 3.6 Flow chart photometer
3.3.2 Measuring principle for hemoglobin determination
The hemoglobin in the blood is photometrically determined. To avoid serious
environmental load, the sodium dodecyl sulfate method is used instead of the
hemoglobin cyanide method.
The photometer unit, consisting of LED, flow cuvette, interference filter, photo
detector and electronic evaluation unit, is arranged in front of the biosensor and
the pump. These are used to determine an extinction equivalent value for the
sample solution. The dependence of the extinction on the concentration is
described by the Lambert-Beer-Bouguer law. Under the constraints defined
there, the size of the extinction is proportional to the material concentration.
Determining hemoglobin
The hemoglobin is released from the erythrocytes by the haemolysis which takes
place in the reaction cup after addition of the sample. This reacts with the
sodium dodecyl sulfate contained in the solution in the cup to produce a stable
colour complex.
The pump is used to add the resulting sample solution to the flow cuvette and
the extinctionequivalent quantity is produced with a wave length of 530 nm. With
the aid of a mathematical function, the hemoglobin concentration of the sample
is calculated and produced from this quantity. The parameters for the
mathematical function have been produced by measuring samples with known
hemoglobin content and securely stored in the equipment.
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