Flow-injection spectrophotometric determination of copper using bis(cyclohexanone) oxalyldihydrazone

Copper can be determined spectrophotometrically at 600 nm based on the reaction of copper(II) and bis(cyclohexanone)oxalyldihydrazone using flow-injection analysis. The carrier stream was distilled water and the reagent streams were 27% (frsol|w/v) citric acid solution, 37% (frsol|v/v) ammonia solution and 0.18% (frsol|w/v) bis(cyclohexanone)oxalyldihydrazone solution. The calibration graph was linear up to 20 μg ml−1 copper and the relative standard deviation for the determination of 5 μg ml−1 of copper was 0.92% (n = 10), the detection limit was 0.13 μg ml−1 copper, both based on injection volumes of 250 μl. The system has been applied to the determination of copper in steels, copper-based alloys and pig feeds and to monitoring copper in an alkaline scale removal process.