Method for determination of calcium in serum, parotid fluid and urine in the weightless state.

Since the Manned Orbiting Laboratory program includes onboard monitoring of calcium metabolism, a method suitable for this determination under conditions of weightlessness has been investigated. Most techniques for calcium assay that are used at the present time have certain disadvantages that would preclude their use under conditions of weightlessness; whereas the nuclear fast red (NFR) technique of Baar, as modified by Kingsley and Robnett, is simple, and all steps in the procedure are compatible with performance in the weightless state. The possible interference of magnesium, hemolysis, and protein was investigated. These effects should be minimal unless drastic changes in magnesium and/or protein levels should occur. The interference by hemolysis may be obviated by the use of a proper blank. The method has been adapted to an apparatus to effect mixing in the weightless state and is regarded as a practicable first-generation method for monitoring calcium metabolism.