How does a blood chemistry analyzer work?

A blood chemistry analyzer is an instrument that performs biochemical assays on clinical samples such as blood serum, plasma, urine, and cerebrospinal fluid and other biological fluids to detect the presence of analytes related to body metabolism, disease, or drugs. These kits are used in a variety of institutions, including small clinics, research laboratories, and large clinical laboratories.

Analytes that are frequently determined on these instruments include enzymes, substrates, electrolytes, specific proteins, drugs of abuse, and therapeutic drugs. The results provide physicians with information on kidney, heart, and liver function and toxicology.

How a blood chemistry analyzer works

They can have two modes of use, semi-automatic or automatic. The semi-automatic ones are ideal for small laboratories where you work with small volumes, while the automated analyzers are suitable for medium and large laboratories, where large quantities of samples are analyzed.

Semi-automatic analyzers analyze one sample after another. Unlike the automatic analyzers that have a different structure, with two spaces:

  • A rack where the reagents are placed.
  • A rack where the samples are placed.

Automated blood chemistry analyzers maximize performance, improve user safety against biological hazards, and decrease the risk of cross contamination. The samples are loaded into the equipment and the tests are scheduled by the user. A probe measures an aliquot of sample and places it in a reaction vessel. Reagents are added from a refrigerated supply on board. Incubation time is allowed, if necessary; then the photometric or ion selective electrode (ISE) test determines the analyte concentration. Results are displayed on the screen or sent to a printer or computer.

Assays and analytical methods

There are several analytical methods of measurement, although a blood chemistry analyzer can offer several principles of measurement. They are divided into two categories:

Optical techniques


It is the most common method. The sample is mixed with the appropriate reagent to produce a reaction that results in a color. The concentration of the analyte determines the intensity of the color obtained.


Light is projected onto the sample with a suitable wavelength, while a photodetector, located on the other side of the sample, measures the amount of absorbed light. It is directly related to the concentration of the analyte in the sample.

Electrochemical techniques

Through direct potentiometry where ion selective electrodes (ISE) are used for the determination of ions in samples such as sodium, potassium, chlorine, and lithium, ISEs are sensors capable of determining the concentration of ions in a solution measuring current flow through an ion selective membrane and also indirect potentiometry using ion selective electrodes.

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