Solid-liquid Separation after Liquid-liquid Extraction. Spectrophotometric Determination of Copper after Extraction of Its Oxine (8-hydroxyquinoline) Chelate with Melted Naphthalene

A new method of liquid-liquid extraction of copper oxinate with melted naphthalene followed by solid-liquid separation has been proposed by Fujinaga et al for the trace analysis of copper. In this experiment, the pH of sample solution was adjusted to 3.5-12 after oxine solution was added. The solution was then heated on a water bath at about 90°C, shaken vigorously after the addition of naphthalene as the solvent to extract copper oxinate, and stood still at room temperature. The solidified naphthalene phase was washed with distilled water by decantation, dissolved and diluted to a definite volume with benzene. The optical absorbancy at 420 nm was measured to determine the amount of copper. Beer's law was obeyed with the amount of copper up to 100 μg in 10ml of benzene