Rapid Modified Eriochrome Cyanine R Method for Determination of Aluminum in Water

Abstract

This study developed a rapid, sensitive, accurate method for the determination of small amounts of aluminum in water. The method uses an eriochrome cyanine R dye that is a modification of Knight's method. The key factors in the modification are adjustment of the dye solutions and elimination of alkalinity, which, even in “trace” amounts, has a marked inhibitory effect. Other interferences are also eliminated, including iron and manganese with ascorbic acid, complex phosphates by boiling with acid, and fluoride, removed either by volatilization or by adding known concentrations of the ion to the aluminum solutions used in preparing calibration curves. Data are also presented to show that glass wool, absorbent cotton, and most filter papers remove nearly all the soluble aluminum from an aluminum solution. Only membrane filters can be used with confidence for this purpose. Finally, using the PSW modified method, it has been possible to demonstrate that aluminum concentrations of 0.05 mg/l or less can be expected in the filter effluent from a well‐operated water treatment plant.