Which reagent is used to determine the concentration of serum inorganic phosphate?

Which reagent is used to determine the concentration of serum inorganic phosphate?

• A. Ehrlich's reagent
• B. Ammonium molybdate
• C. 8-Hydroxyquinoline
• D. Bathophenanthroline

Answer: (B)

In colorimetric measurement of serum inorganic phosphate, the key step is forming a phosphomolybdate complex by reacting phosphate with ammonium molybdate in acidic conditions. This complex is then reduced to molybdenum blue, producing a intense blue color whose intensity is proportional to the phosphate concentration. Because this blue complex forms specifically from phosphate under these conditions, ammonium molybdate is the reagent that enables accurate quantification of inorganic phosphate in serum. The other reagents listed are used in different types of colorimetric assays: Ehrlich's reagent is associated with tests like urobilinogen detection, 8-hydroxyquinoline acts as a metal chelator in various assays, and bathophenanthroline is used in iron determinations to form a colored Fe(II)–bathophenanthroline complex.

In colorimetric measurement of serum inorganic phosphate, the key step is forming a phosphomolybdate complex by reacting phosphate with ammonium molybdate in acidic conditions. This complex is then reduced to molybdenum blue, producing a intense blue color whose intensity is proportional to the phosphate concentration. Because this blue complex forms specifically from phosphate under these conditions, ammonium molybdate is the reagent that enables accurate quantification of inorganic phosphate in serum. The other reagents listed are used in different types of colorimetric assays: Ehrlich's reagent is associated with tests like urobilinogen detection, 8-hydroxyquinoline acts as a metal chelator in various assays, and bathophenanthroline is used in iron determinations to form a colored Fe(II)–bathophenanthroline complex.