Albumin concentration is commonly measured by which dye-binding method?

• A. Dye binding
• B. Salting out
• C. Optical density
• D. Precipitation

Answer: (A)

Albumin concentration is determined with a dye-binding colorimetric assay because albumin binds specifically to certain acidic dyes, forming a colored albumin-dye complex whose intensity reflects how much albumin is present. Dyes like bromocresol green or bromocresol purple are used; after mixing the sample with the dye, the bound complex turns a color whose absorbance is measured with a spectrophotometer. A standard curve generated from known albumin concentrations lets you calculate the albumin level in the sample. This approach is favored for its speed, simplicity, and cost-effectiveness, and it directly links color change to the amount of albumin, unlike methods based on salting out (which relies on precipitation), or general optical density without a specific binding reaction. Precipitation alone can separate proteins but doesn’t provide a direct dye-bound color measurement for albumin.