254 



Scientific Proceedings (129) 



120 (2080) 



A criticism and modification of the MacLean blood sugar method. 

 By A. BAIRD HASTINGS and ALEITA HOPPING. 



[From the Department of Physiology, Columbia University, New 



York City.] 



The titrimetric method for the determination of blood sugar 

 proposed by Maclean 1 in 1919 has been used with success in 

 a number of researches both abroad and in this country. Its 

 simplicity, accuracy and the small amount of blood required 

 recommend it to those who prefer titrimetric to colorimetric 

 quantitative determinations. Briefly, the principle of the Mac- 

 Lean method is : 



1. Removal of the proteins by heating oxalated blood with 

 acidified sodium sulphate, adding colloidal iron, and filtering. 



2. Boiling, under standardized conditions, an aliquot part of 

 the filtrate with a known amount of an alkaline copper solu- 

 tion containing potassium iodide and potassium iodate. 



3. Titration of the iodine liberated upon acidification with 

 standard thiosulphate. 



Since, under the conditions defined by MacLean, the cuprous 

 salt reduced by the sugar is oxidized by the iodine liberated, the 

 excess iodine titrated with thiosulphate is inversely proportional 

 to the amount of reduction. Empirical factors can, therefore, be 

 determined converting the volume of thiosulphate used into con- 

 centration of glucose. 



It was found, however, that by MacLean's method the deter- 

 minations of sugar in freshly drawn blood to which no anti- 

 coagulant had been added gave values distinctly higher than 

 those determined on the same blood which had been oxalated, 

 (Table I). 



TABLE L 



Sugar determinations of blood to which K2C2O4 had been added and had not 



been added. 







Concentration of 



sugar in 



mgs. per 



100 c.c. of blood. 



Method. 



Dog. 



K 2 C 2 04 present. 



K2C2O4 not present. 







a 



b 



Average 



a 



b 



Average 



Original 



A 



.105 



100 



103 



89 



88 



89 



MacLean 



B 



91 



92 



92 



55 



55 



55 



Modified 



C 



90 



85 



83 



90 



85 



88 



MacLean 



D 



93 



90 



95 



93 



93 



93 



1 MacLean, H., Biochem. J., 1919, xiii, 135. 



