Bilirubin oxidase method measures decreased absorbance at which wavelength range?

• A. 405-460 nm
• B. 450 nm
• C. 560 nm
• D. 600 nm

Answer: (A)

Bilirubin has its strongest light absorption in the visible region near 450 nm. In the bilirubin oxidase method, bilirubin is oxidized to biliverdin, so the chromophore that gives the absorbance around 450 nm is diminished. Because spectrophotometers use a bandwidth rather than a single exact wavelength, the absorbance decrease is measured over a practical range that captures this peak, typically about 405–460 nm. Wavelengths like 560 nm or 600 nm are outside bilirubin’s absorption band and won’t show the expected drop, while 450 nm lies within the useful range but is usually reported as part of the broader 405–460 nm window.