Features of sodium determination in dilute mixed solutions with phenylalanine by flame photometry

Abstract

Flame spectrophotometry is one of the main methods for determining alkali and alkaline earth metals in solutions. Chemical analysis by the flame photometric method have become of great importance for estimation of trace elements content and for work on small quantities of sample. The most important disadvantages of flame spectrophotometry are different types of interference (spectral, chemical, and physical). The paper considers mainly the physical interference which directly relates to the state of the sample itself and includes solution temperature, viscosity, surface tension, and vapor pressure. These effects are interdependent and not easily isolated for study. The addition of a substance increases the viscosity of the solution, which affects aerosol formation, transport, droplet size distribution, evaporation rate and flame temperature. All that leads to a decrease in the intensity of light emission. In the present article, the effect of phenylalanine on the sodium determination by the flame photometric method in the field of dilute solutions was studied. A decrease in the photocurrent emission of sodium in its joint determination with phenylalanine was found. The main reason is the increase in viscosity. It leads to a reduction in the spraying rate in the analyzer and a diminution in the analytical response of the device. The systematic type of errors in determining the concentration of sodium in the presence of phenylalanine is proved.