A manual method is described for determining the hydrogen peroxide produced from uric acid with uricase (pH 9.2) after deproteinization of 1.00 ml of serum. In the method, 2,4,6-tribromophenol is coupled with 4-aminoantipyrine (pH 7.0) by peroxidase oxidative coupling. The sensitivity of the method is such that 25 µg of uric acid from a fourth of the deproteinized serum (100 mg/liter) in a final volume of 5 ml of n-butyl acetate color extract gives a stable absorbance of 0.7 at 492 nm with a 1-cm cell. The method is reproducible, and many substances that may be encountered in serum do not interfere. Absorbances are linear for uric acid concentrations as high as 200 mg/liter.

The hydrogen peroxide produced from glucose by glucose oxidase action at pH 7 is determined by the peroxidase oxidative coupling of N,N-diethylaniline with 4-amino-antipyrine. A 20-µl sample of plasma or serum is reacted at room temperature for 10 min. The sensitivity of the method is such that 60 µg of glucose (300 mg/dl) in a final volume of 5 ml gives an absorbance of 0.8 at 553 nm with a 1-cm cell. Absorbances are linearly related to glucose concentrations as high as 10.00 g/liter.

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