Oxyhemoglobin is corrected by determining its absorbance at which wavelength?

• A. 410 nm
• B. 450 nm
• C. 510 nm
• D. 610 nm

Answer: (A)

The key idea is that hemoglobin has a strong, characteristic absorbance in the Soret band around 410 nm because of the heme porphyrin ring. Measuring absorbance at this wavelength provides a reliable signal that reflects the presence of hemoglobin and serves as a stable reference to correct or normalize other measurements. In practice, this 410 nm signal is used to correct for the contribution of oxyhemoglobin (and other Hb forms) when calculating or distinguishing between species, while the different wavelengths in the visible range (where oxy- and deoxyhemoglobin differ more) are used for determining oxygenation status. The 410 nm region is chosen specifically for this correction because of its strong, consistent absorption by Hb’s heme moiety, making it the most effective reference point among the options listed.