Automated fluorometric method for the determination of serum calcium.

A. FULLY automated nlethod for the (leterinination of serum calcium which is accurate, reproducible, and relatively simple seemed desirable. The additioll of the fluorometer (1) to the modular system of the AutoAnalyzer* suggested the search for a fluorometric calcium procedure. Accordingly, several substances known to complex with calcium were obtained and their fluorescent emission spectra in acid, neutral, and alkaline solutions with and without calcium and magnesium present were obtained. One of these substances, fluorescein-complexone was found to fluoresce ill strongly alkaline solution in the presence of calcium but not magnesium. This communication describes a method for the determination of calcium in serum, using fluorescein-complexone, which has proven rapid, reproducible, accurate, and dependable for use in a clinical chemistry laboratory. With this method, 0.1-ml. samples were analyzed at a rate of 60 per hour, and results were comparable with those obtained with the classical oxalate precipitation and permanganate titration as modified by Clark and Collip (2).