Bromcresol purple at a pH of 5.2 is used in a colorimetric method to measure which protein?

• A. Albumin
• B. Globulin
• C. Bence Jones protein
• D. Immunoprotein

Answer: (A)

Bromcresol purple colorimetric measurement relies on dyes that form a colored complex with a specific protein. At pH 5.2, bromcresol purple binds preferentially to albumin, producing a color change whose intensity tracks the albumin concentration in serum. The pH condition enhances the dye’s affinity for albumin while minimizing binding to other serum proteins, so the optical signal mainly reflects albumin rather than globulins, Bence Jones protein, or other immunoproteins. That specificity is why this dye is used to quantify albumin in clinical chemistry.