IV. DETERMINATION 91 



by Morton and Stubbs.^'^ The estimation in foodstuffs is in most cases 

 possible only after saponification and chromatography. Thus, a method for 

 determination in dried eggs, which describes the separation of vitamin A 

 from xanthophylls in egg yolk, was worked out l)y Thompson et alP and 

 by Schrenk (/ al.-^ Mann," as well as Raynes and McLellan,'-^ give a de- 

 scription for the determination of the vitamin A content of vitaminized 

 cocoa and chocolate goods. The vitamin A and carotene content of milk, 

 butter, and margarine has been discussed in many investigations.^^-^^ Uni- 

 versally applicable prescriptions for the determination in fish liver oils, 

 margarine, butter, milk, and other foods have been i)ul)lished by Gridgeman 

 and his collaborators^^ and by Hjarde.-' Both use the chromatographic 

 adsorption method for the purification of the vitamin A. 



As mentioned before, fish liver oils often show irrelevant absorption. 

 Therefore, a series of investigations was carried out to make the determina- 

 tion more specific, by testing the material in the usual way, then destro3ing 

 the \'itamin A through oxidation, and again measuring spectrophotometric- 

 ally. From the difference, the vitamin A content may be calculated.'*^ ■ ^^ 

 But these methods cannot be credited A\'ith special importance. Somewhat 



^* H. R. Rosenberg, Chemistry and Physiology- of the Vitamins. Interscience Pub- 

 lishers, New York, 1945. 



25 C. R. Thompson, M. E. Ewan, S. M. Hauge, B. B. Bohren, and F. W. Quacken- 

 bush, Ind. Eng. Chetn. Anal. Ed. 18, 113 (1946). 



26 W. G. Schrenk, D. S. Cliapin, and R. INI. Conrad, Ind. Eng. Chem. Anal. Ed. 16, 

 632 (1944). 



2' T. B. Mann, Analyst 68, 233 (1943). 



28 E. G. Raynes and B. G. McLellan, Analyst 68, 109 (1943). 



29 P. D. Boyer, R. Spitzer, C. Jensen, and P. H. Phillips, Ind. Eng. Chem. Anal. Ed. 

 16, 101 (1944). 



^o J. Effern, Vorratspflege u. Lehensmitteljorsch . 3, 53 (1940). 



" F. R. Olson, D. M. Hegsted, and W. H. Peterson, J. Dairy Sci. 22, 63 (1939). 



32 M. Hochberg, /. Dairy Sci. 31, 315 (1948). 



" L. Skurnik and M. Hellen, Z. Vitaminforsch. 15, 52 (1944). 



" F. P. Zscheile, R. L. Henry, J. E. White, Jr., H. A. Nash, C. L. Shrewsbury, and 



S. M. Hauge, Ind. Eng. Chem. Anal. Ed. 16, 190 (1944). 

 " F. P. Zscheile, H. A. Nash, R. L. Henry, and L. F. Green, Ind. Eng. Chem. Anal. 



Ed. 16, 83 (1944). 

 3« W. Wodsak, Pharmazie 4, 370 (1949). 



" A. E. Sobel and A. A. Rosentag, Anal. Chem. 21, 1.540 (1949). 

 3« P. B. Midler and H. Moor, Mill. Gehiete Lebensm. u. Hyg. 40, 358 (1949). 

 39 J. B. Wilkie, J. Assoc. Offic. Agr. Chemists 30, 382 (1947). 

 "» I. L. Bowen, N. T. Gridgeman, and G. F. Longman, Analyst 71, 20 (1946). 

 " J. R. Edisbury, Aimlyst 65, 484 (1940). 

 « T. W. Goodwin and R. A. Morton, Analyst 71, 15 (1946). 

 « W. Heimann, Z. Untersuch. Lebensm. 85, 502 (1943). 

 " A. Fujita and T. Sakamoto, Biochem. Z. 308, 344 (1941). 

 « G. T. Jones and R. T. Harris, Analyst 68, 8 (1943). 



