Based on spectrophotometric measurement of cyanide derivative of hemoglobin.
- Blood is mixed with a solution containing potassium cyanide and potassium ferricyanide (Drabkin’s solution).
- The red blood cells are lysed, producing an evenly disturbed hemoglobin solution.
- Potassium ferricyanide transforms hemoglobin into methemoglobin, and methemoglobin combines with potassium cyanide to produce hemiglobincyanide (cyanmethemoglobin).
- Cyanmethemoglobin has a peak absorbance at 540 nm and is measured photometrically.
- The absorbance is compared with that of the standard hemiglobincyanide solution by using a formula to obtain the amount of hemoglobin.