Simultaneous determination of methemoglobin and total hemoglobin by a continuous-flow method.

We describe a sensitive, accurate automated method for the simultaneous measurement of methemoglobin and total hemoglobin in blood. The method can be used for either continuous in vivo monitoring or intermittent sampling at a rate of 20/h. Standardization procedures are described, in which human blood treated with sodium nitrite is used. Repeatability of methemoglobin and total hemoglobin measurements, expressed as coefficient of variation in percent, are within ±4.1 and ±2.6%, respectively. Normal methemoglobin concentration’s in humans and dogs did not exceed 0.55 g/dl (3.3% of the total hemoglobin).