Atomic Absorption Spectrophotometry of Rubidium in Biological Fluids

Abstract The atomic absorption spectrophotometric method for measurement of rubidium in serum, plasma, whole blood, and urine was evaluated, and the effects of interfering ions were studied. Absorbance was most enhanced by potassium and sodium; calcium, bicarbonate, and chloride at the concentrations found in serum did not affect rubidium absorption. Naturally occurring rubidium concentrations in serum, plasma, whole blood, and urine are 3, 4, 70, and 18 µEq/liter, respectively, much lower than expected therapeutic concentrations. Methods for preparing standards, optimum instrument settings, and special treatment of samples were established with specimens from monkeys treated with rubidium. These procedures are applicable to human bloods from patients receiving rubidium therapy when such therapy is begun for treatment of affective disorders.