[Microflame-photometric estimation of sodium and potassium for testing the purity of inner ear fluids (author's...

A simple micromodification of simultaneous flame-photometric estimation of sodium and potassium concentration in sample volumes of 0.1 microliter is described for testing the purity of inner ear fluids, especially of perilymph. The precision of the method is about 10% (calibration standards, Table 2) and depends mainly on the precision of measuring the small sample volumes. The method has been used for examining cerebrospinal fluid, perilymph, and endolymph samples of guinea pigs. The increased perilymphatic potassium (Fig. 1a) and endolymphatic sodium values suggest a more or less substantial contamination of the tested samples and underline the necessity of checking the purity of inner ear fluid samples which are used in biochemical analysis.