Drabkin's Reagent is used for the quantitative, colorimetric determination of hemoglobin concentration in whole blood at 540 nm. Drabkin's Solution reacts with all forms of hemoglobin except sulfhemoglobin, a pigment that normally occurs in only minute concentrations in blood.

Drabkin′s reagent is used in measuring haemoglobin from blood samples. It comprises potassium ferricyanide, potassium cyanide and potassium dihydrogen phosphate as components. Potassium ferricyanide oxidizes haemoglobin to methemoglobin and then to cyanmethemoglobin.

To all tubes, add 5.0 ml of the Drabkin's Solution. 4. To each tube labeled Test, add 20 µl of the whole blood sample, rinsing the pipette 3-4 times with reagent. Mix well and allow to stand for at least 15 minutes at room temperature

The principle of this method lies in conversion of hemoglobin to cyanmethemoglobin by the addition of Potassium cyanide and ferricyanide whose absorbance is measured at 540 nm in a photoelectric calorimeter against a standard solution. 

DRABKIN S SOLUTION DILUENT