Sensitive, direct colorimetric assay for copper in serum.
We have developed a sensitive procedure for determination of serum copper by use of the color reagent 4-(3,5-dibromo-2-pyridylazo)-N-ethyl-N-sulfopropylaniline. After mixing serum sample and reagent, and incubating at 37 degrees C for 5 min, we measure the absorbance of the resulting chelate complex at 580 nm (molar absorptivity, 80,000 L.mol-1.cm-1). Results of the method varied linearly with copper concentration to at least 5 mg/L; the lower limit of detection was 0.1 mg/L. Within-run CVs were 1.6% and 3.3% for copper concentrations of 1.03 and 0.72 mg/L, respectively (n = 10 each). Between-run CV was 2.8% at 1.22 mg/L (n = 14). Results of the proposed method (y) correlated well with those determined by standard atomic absorption spectrophotometric techniques (x): y = 0.99x - 0.02 mg/L; Syx = 0.08; r = 0.977; n = 56. Iron, zinc, cadmium, cobalt, and lead do not interfere.
Abe
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Department of Laboratory Medicine, Gifu University School of Medicine, Japan.
Yamashita
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Noma
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D000814:Aniline Compounds; D001205:Ascorbic Acid; D001391:Azo Compounds; D002614:Chelating Agents; D003124:Colorimetry; D003300:Copper / Q000097:blood*; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D011786:Quality Control; D013053:Spectrophotometry
D000814:Aniline Compounds; D001391:Azo Compounds; D002614:Chelating Agents; D007202:Indicators and Reagents; C059185:4-(3,5-dibromo-2-pyridylazo)-N-ethyl-N-sulfopropylaniline; D003300:Copper; D001205:Ascorbic Acid