When mixed with phosphotungstic acid, which compound causes reduction to a tungsten blue complex?

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Enhance your knowledge with the Ciulla Clinical Chemistry Test. Study with interactive quizzes, featuring flashcards and multiple-choice questions. Each question offers hints and explanations for better understanding. Prepare effectively and excel in your exam!

Multiple Choice

When mixed with phosphotungstic acid, which compound causes reduction to a tungsten blue complex?

Explanation:
The test hinges on a redox reaction where phosphotungstic acid is reduced to form a blue tungsten complex when a reducing substance is present. Uric acid can readily donate electrons under the assay conditions, becoming oxidized and reducing the phosphotungstate to the blue tungsten complex. This distinctive color change signals a positive result for a reducing substance in the sample. The other substances listed—urea, ammonia, and creatinine—do not act as reducing agents strong enough to reduce phosphotungstic acid here, so they do not produce the tungsten blue color.

The test hinges on a redox reaction where phosphotungstic acid is reduced to form a blue tungsten complex when a reducing substance is present. Uric acid can readily donate electrons under the assay conditions, becoming oxidized and reducing the phosphotungstate to the blue tungsten complex. This distinctive color change signals a positive result for a reducing substance in the sample. The other substances listed—urea, ammonia, and creatinine—do not act as reducing agents strong enough to reduce phosphotungstic acid here, so they do not produce the tungsten blue color.

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