A Simple and Accurate Internal Standard Flame Photometer for the Determination of Sodium and Potassium in Biological Fluids

Abstract

One of the authors (Leppänen) had previously developed a simple flame photometer with two photocells, based on the internal standard principle (V. Leppänen & O. Forsander, Flame-Photometric Determinations of Potassium and Sodium in Biological Fluids. — Scandinav. J. Clin. & Lab. Investigation 1951, 3, 33). Since, however, this apparatus was found to have some technical drawbacks in continuous use, two of the authors (Leppänen & Krusius) intended to use another simple type of flame photometer, with only one selenium photocell (flame photometer proposed by Riehni & Lange, Model 2, Dr. B. Lange, Berlin— Zehlendorf. See H. Riehm & B. Lange, Bestimmung von Kalium, Natrium, and Calcium im Flammenphotometer nach Riehm-Lange. — Ztschr. f. anal. Chem. 128, 1948). Experience with this photometer showed, however, that it was not suitable for clinical use. The authors, therefore, designed a new simple flame photometer in collaboration with a radiotechnical specialist (Mettinen). The new flame photometer is based on the internal standard principle and uses vacuum photocells (type Mullard 90 and CV 90). The apparatus operates by ordinary domestic coal gas, the light emission of which is rendered monochromatic by means of interference filters and measured by the photocells. The electric impulses are compensated against each other, and the difference between them is amplified by a special amplifier and measured by a sensitive galvanometer. A high vacuum pump acts as an air compressor and gives a satisfactory and steady pressure to the atomizer. There are special valves to regulate both air and fuel pressure. This relatively simple apparatus is suitable for the clinical determination of potassium and sodium in both plasma (sera) and erythrocytes, but it can also be used for the examination of other biological fluids. The accuracy of the apparatus is demonstrated by calibration curves for potassium and sodium standard solutions, by control determinations, and by analyses with known amounts.