Determination of copper oxinate used as fungicide and antiseptic

Abstract

In the work reported by Darbey, the sample was treated with hot dilute hydrochloric acid to leach the contained oxine. Then, the color intensity of the solution was measured at 365 mμ. However, this method is seriously affected by iron and also by some organic substances, which show appreciable absorption at 365 mμ.
In the present method recommended by the authors, the sample is treated with phosphoric acid in order to eliminate the absorption of iron (Fig. 1-(3)), and the absorbancy of the solution is directly measured at 360 mμ (1st procedure). When colored organic materials are present in the sample, the following method is recommended (2nd procedure). The acid solution (oxine<1.5 mg) is treated with copper sulfate solution, and the pH is adjusted to about 5. Then the extraction is made with a definite volume of chloroform, and the absorbancy of the extract is measured at 410 mμ. Oxine is determined by the use of a prepared calibration curve.
On the other hand, copper is estimated with oxine by the extraction-differential photometric method: oxinates of copper and other materials contained in the sample are simultaneously extracted with a definite volume of chloroform. Then the extracted chloroform solution is divided into two fractions. One fraction is washed with about 10 ml of potassium cyanide solution (pH 89, saturated with chloroform) to remove the copper. The absorbancy of the other fraction is measured at 410 mμ using this washed one as reference. Copper is determined by the use of a prepared calibration curve.
Very satisfactory results were obtained with this method.