A colorimetric method for the determination of carboxyhaemoglobin over a wide range of concentrations.

A colorimetric technique for the determination of carboxyhaemoglobin in blood is described. Carbon monoxide released from blood in a standard Conway unit reacts with palladous chloride/arsenomolybdate solution to produce a blue colour. Using 0.5 to 2 ml. of blood, the method will estimate carboxyhaemoglobin accurately at levels from 0.1% to 100% of total haemoglobin and in the presence of other abnormal pigments.A number of methods are available for the determination of carboxyhaemoglobin; none is accurate below a concentration of 1.5 g. carboxyhaemoglobin per 100 ml. but for most clinical purposes this is not important. For forensic purposes and occasionally in clinical use, an accurate determination of carboxyhaemoglobin below 750 mg. per 100 ml. may be required and no really satisfactory method is at present available. Some time ago when it was important to know whether a person who was found dead in a burning house had died before or after the fire had started, we became interested in developing a method which would determine accurately carboxyhaemoglobin at levels of 750 mg. per 100 ml.