The microdetermination of biological copper with oxalyldihydrazide

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Abstract
Methods are described for the determination of microgram quantities of biological copper in aqueous medium as the intensely coloured oxalyldihydrazide-acetaldehyde complex (molar extinction coefficient 23,000 to 23,500). The methods are applicable on a routine basis to any biological material, in particular to serum, urine, or tissues, such as liver, brain, or kidney. In the case of urine a simple semi-quantitative screening method is also described. For quantitative work copper is liberated from serum by acid extraction and protein precipitation, and from urine and tissues by a rapid wet-ashing procedure. Recoveries of added copper from urine are quantitative. Precision is high although day-to-day control with standards and blanks is desirable. The methods are applied in an investigation of the diurnal variations in a normal man and in two cases of Wilson's disease.