The precision of a direct-reading flame photometer for the determination of sodium and potassium in biological fluids

Publisher Website
Google Scholar
Abstract
The flame spectrum was analyzed and efficiency of the filter combinations assessed. The operation of diluting and reading of samples containing 2-5[mu]g. Na or K/ml. has a mean standard deviation of 0.03 [mu]g./ml. The validity of Na and K estimations in urine and serum, by direct comparisons with standard solns. of NaCl or KC1, was assessed by addition expts., comparison with chemical methods and serial dilutions. Urinary Na and K estimations are free from interference at sample dilutions between 1:300 and 1:1000. At lower dilutions, readings of both Na and K are depressed. Serum Na estimations are free from interference, but serum K estimations (dilution 1:100) are subject to a systematic error of +13% of the chemical estimation. Estimations accurate to [plus or minus] 1.5% can be made by applying an arithmetical correction. At lower dilutions, progressive depression of the K reading occurs.