The application of flame photometry to sodium and potassium determinations in biological fluids.

The need for a rapid, accurate method to determine quantitatively Na and K present together in biological fluids has been met by the procedures to be described. The necessity of separating these elements prior to their determination by the various chemical methods usually employed has led to procedures which are often prohibitively tedious and time-consuming. The recent development of flame photometry has now made possible physical methods of analysis in which chemical separation of Na and K is unnecessary (1, 2). Although we are dealing with Na and K determinations only, the principle of flame photometry originally used by Lundegardh (3-5), and modified and called the air-acetylene flame method by Cholak and Hubbard (6), can theoretically be applied to the determination of all the alkaline metals. At present the available commercial instruments employ a relatively low temperature flame which activates the ions rather than the metals themselves; the sensitivity of the photocells is such that the lines of the metals themselves would not be of sufficient intensity to measure, and suitable optical filters for other metals are not readily available. The present report concerns the use of the Perkin-Elmer flame photometer (model lS)l in sodium and potassium determinations on blood, plasma, red blood cells, and urine.