Glass electrode measurement of cerebrospinal fluid sodium and potassium

A routine p h meter and accessories have been modified for measuring sodium and potassium by the glass electrode method. CSF sodium and potassium concentrations measured by both the glass electrode and flame photometer have been compared. The mean concentration of sodium and potassium as measured by the electrode was 143/2.4 and by the photometer, 145/2.7. The average γ csf Na + + K + was 0.745. The average a Na + was 108.03, average a K +, 2.01. The relationship between the concentrations as determined by the electrode and photometer is expressed by the equation Y = 0.888 X + 14.35 ± 1.36 for sodium and Y = 0.980 X − 0.24 ± 0.21 for potassium.