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Electrolytes, Blood Gases, and Blood pH

Clinical Chemistry

  1. Robert C. Elser

Published Online: 15 SEP 2006

DOI: 10.1002/9780470027318.a0515

Encyclopedia of Analytical Chemistry

Encyclopedia of Analytical Chemistry

How to Cite

Elser, R. C. 2006. Electrolytes, Blood Gases, and Blood pH. Encyclopedia of Analytical Chemistry. .

Author Information

  1. York Hospital, York, USA

Publication History

  1. Published Online: 15 SEP 2006


The term electrolytes, in the clinical sense, refers to the principal ionic constituents of blood: sodium (Na+), potassium (K+), chloride (Cl), and bicarbonate (HCO3). Technology for the measurement of these ions has evolved from colorimetric and spectrophotometric methods to ion selective sensors. With the evolution of the technology has come an important reduction in the quantity of sample required to make the determination of concentrations of the ions in blood.

The assessment of respiratory function and the acid–base balance of the blood is accomplished by the measurement of pH, PCO2, and PO2. These measurements are usually not made singly, but rather as a combination of determinations made at the same time on the same blood sample.

In critically ill persons, these seven analytes are of major diagnostic importance.