Fluorometric ultramicrodetermination of calcium in biologic fluids.

HE PURPOSE OF THIS PAPER 5 to describe a micromethod for the fluorometric determination of calcium in blood serum, plasma, urine, and cerebrospinal fluid. The method is an adaptation of the fluorometric procedure of Wallach et al (1, 2) and Kepner and Hercules (3) to the TJnopette system* (4, s). The original procedure involved the preparation of a stock solution of Calcein or fluorescein complexone, 1 mg/ml, in 0.8 N potassium hydroxide. This solution is stable 30 days at 4#{176}. The working reagent, prepared to contain 33 g of Calcein or fluorescein complexone in 5 ml of 0.8 N potassium hydroxide is stable only 4-I days at room temperature. The reagents in the Unopette system adaptation of the procedure are stable indefinitely at room temperature. All the reagents for a single determination are premeasured and prepackaged: 5.0 ml of the 0.8 N potassium hydroxide in a Unopette reservoir, and 35 g of Calcein in dry form in a 2O-j.ml Unopak. The Calcein and sample are added to the diluent simultaneously. The procedure is outlined in Fig. 1.