Increase in the sensitivity of the fluorescent reaction of the complexing of aluminium with morin using surfactant agents

Abstract

The effects of surfactants on fluorescence analysis were studied. The addition of non-ionic surfactants (ethylene oxide - propylene oxide condensates) to a metal complex solution causes a remarkable enhancement of fluorescence, by which means the sensitivity of the fluorimetric determination of aluminium is increased ten-fold over conventional methods.

The optimum conditions in which the increase in fluorescence intensity is produced were studied and are as follows: 3% surfactant, pH 3.8 in acetic acid - acetate buffer at 25 °C; and the intensity of fluorescence is measured at 495 nm and excited at 430 nm. Using a morin concentration of 0.005% in the solution under analysis, the calibration graph is linear up to 35 p.p.b. (35 parts in 10⁹) of aluminium. The relative standard deviation for the analysis of ten replicates of a solution containing 2 p.p.b. of aluminium is 3%; when it contains 10 p.p.b. the relative standard deviation is 2%.

The detection limit of the method is 0.2 p.p.b., using an excitation slit of 10 nm and an emission slit of 5 nm.

From the study of interfering ions it was deduced that the presence of surfactants gives a higher selectivity than a conventional method.