Fluorimetric determination of potassium ion using hexadecyl-acridine orange immobilized on a poly(vinyl chloride) membrane attached to a flow-through cell

A cationic fluorescent probe of hexadecyl-acridine orange is immobilized on a poly(vinyl chloride) membrane containing valinomycin. The membrane is attached to the inner wall of the flow-through cell in a fluorescence spectrometer, and potassium ion is detected repetitively by a flow injection system without consuming the indicator reagent. The response is proportional to the logarithmic concentration of the potassium ion in the range 0.5-50mM. Fifteen samples are determined in 1 h, and the relative standard deviation of peak height is 2.4% for a sample containing 0.1 μmol (1mM) of potassium ion. The extended Nicolsky equation is applied to the observed peak height, the selectivity coefficient for sodium being 4x10-3. The concentration of potassium ion in human blood plasma is also determined by this system (author). 16 refs.; 2 figs