OTHER METHODS AND ESTIMATION IN PLASMA, URINE, TISSUES 301 



40° C. The sum of hemoglobin derivatives including sulfhemoglobin is 

 determined. 



It is doubtful whether the alkaline hematin method recently recommended 

 (1536) is preferable to the acid hematin method. Since the method involves 

 heating, it is less simple to carry out than the acid hematin method and in 

 addition the color is weaker. The advisability of using hemin for standardi- 

 zation is open to question since the absorption spectrum of the alkaline 

 hematin from hemoglobin differs from that of an alkaline hematin solution 

 (cf. Section iA-i.). The use of this standard has also been found unsatis- 

 factory by Gibson and Harrison (.994), who devised an artificial standard 

 composed of cobaltous sulfate, potassium bichromate, and chromium potas- 

 sium sulfate. Horecker {13^5), however, has recently suggested a method 

 whereby the difficulties involved in using hemin as a standard can be over- 

 come, {cf. also 1320a, 1534a) . 



The colorimetric estimation of carboxyhemoglobin (Haldane method) has 

 been worked out as a British standard method. The Medical Research 

 Council Report of 1943 {1893) has recommended this method, and a standard 

 hemoglobinometer has been designed. A careful reading of the report, how- 

 ever, should convince everyone that the method is far from satisfactory. 

 Quite apart from the fact that the stability of the carboxyhemoglobin solution 

 is open to question, amazingly large errors were found, mainly due to faulty 

 matching. While some of these errors were certainly due to avoidable faults, 

 it has still to be shown that the method is superior to the acid hematin 

 method. It has recently been shown that variation of the intensity of the 

 light used for comparison exerts a marked influence on the exactness of the 

 method, the smallest percentage of errors being obtained at from 5 to 10 foot 

 candles {635). The carboxyhemoglobin method measures only part of any 

 hemj'globin and sulfhemoglobin present. 



The hemiglobin cyanide method is also applicable to the colorimeter 

 (467). Hemin may be used for the preparation of the standard. 



9.5. Other Methods and Estimation of Hemoglobin 

 in Plasma, Urine, and Tissues 



The estimation of total iron has frequently been used for hemoglobin 

 determination in blood. There is, ho^vever, little doubt that blood contains 

 some nonhemoglobin iron, although the amount of this is still a matter of 

 controversy {cf. Chapter X, Section 5.2.). Plasma iron forms only a small 

 part of this, far more nonhemoglobin iron being contained in the erythrocyte. 

 While in normal blood the difference between total iron and hemoglobin iron 

 is probably not significant, the values can be very different in pathological 

 blood; here differences up to 50% have been observed. Sulfhemoglobin and 

 choleglobin are, of course, also estimated as hemoglobin by this method. 



While the determination of iron can be very exact in the hands of an 

 experienced analyst, it is by no means simple and is time consuming. The 

 great divergences in the findings of different authors for the differences 

 between total iron and hemoglobin iron in normal blood (0-8%) raises serious 

 doubts as to whether all investigators have been able to carry out correct 



