Colorimetric Method For Determination Of Sugars And Related Substances

Colorimetric Method for Determination of Sugars and Related Substances
MICHEL DUBOIS,

K. A. GILLES,

J. K. HAMILTON, P. A. REBERS, and FRED SMITH

Division o f Biochemistry, University o f Minnesota, St. Paul, M i n n .

Simple sugars, oligosaccharides, polysaccharides, and their derivatives, including the methyl ethers with free or potentially free reducing groups, give an orangeyellowcolor w-hentreated with phenol and concentrated sulfuric acid. The reaction is sensitive and the color is stable. By use of this phenol-sulfuric acid reaction, a method has been developed to determine submicro amounts of sugars and related substances. In conjunction with paper partition chromatography the method is useful for the determination of the composition of polysaccharides and theirmethyl derivatives.

OLORIMETRIC tests for reducing sugars and polysaccharides have been known for a considerable time. The reagents such as 1-naphthol (33) for carbohydrates in general; benzidine for pentoses and uronic acids (27, 49,50); naphthoresorcinol for uronic acids (61 ); and resorcinol (43), naphthoresorcinol (.%), and resorcinol disulfonic acid (31) for ketoses are well-knon-n examples ofcolorimetric tests that may be carried out in acid solution. Such tests as these and modifications of them using aromatic amines and phenols (4,22, 38) have recently gained added importance since the ext,ensive development, of partition chromat'ography for the separation and characterDETERMIhATION OF COYCENTR4TION OF PURE S C G 4 R SOLUTIOYS izat,ion of minute amounts of sugars and theirderivatives ( 1 , 4, 8, 1 1 , 12, 17, 18, 21-23, 26, S6, 39, 4 7 ) . Polyols and carbohyReagents and Apparatus. Sulfuric acid, reagent grade 95.5%, conforming t o -4CS specifications, specific gravity 1.84. drates with a reducing group may be detected by the Tollens Phenol, 80% by weight, prepared by adding 20 grams of glasssilver reagent (39, 52), perhaps one of the best reagents in the distilled water to80 giams of redistilled reagent grade phenol. art, of chromatography. Reducing sugars are also detectable This mixture forms a v-ater-n-hite liquid that is readily pipetted. by picric acid ( 7 , l 7 ) , 3,4-dinitrobenzoic acid (5), 3,5-dinitroCertain preparations have been known to remain water-white after a years' storage, while others turn a pale yellow in 3 or 4 salicylic acid (6, 32, 48),o-dinitrobenzene (17, 401, and methylene months. The pale yellon- color that sometimes develops does not blue (54), Tvhile diazouracil is said to be specific for sucrose as interfere in the determination, inasmuch as a blank is included. well as oligosaccharides and polysaccharides containing the Coleman Junior, Evelyn, Klett-Summerson, or Beckman sucrose residue ( 4 2 ) . Model DUspectrophotometers. All \vere used with satisfactory results in this inwstigation. Volunietric procedures involving the use of potassium ferricyanide (19), ceric sulfate ( i s ) , copper sulfate (16, 44), and sodium hypoiodite (20) are ap120plicable to the determinat,ion of small amounts of reducing sugars after separation hy parti1.00t,iori chromatography. However, experience s h o w that t,hese methods requireconsiderable skill and are time-consuming and sensit,ive to slight variation in the condit,ions. The anthrone (13, 1 4 , 28, 3dJ 35, 5 3 ) and the 1-naphtholsulfonat,e (10) reagents are excellent for st,andard sugar solut,ions ( 3 $ ) > but, when applied to the anal)-sis of sugars separated by partition chromatography, the presence of only traces of residual solvent drveloper may render themuseless. 3Iost sugars can be separated on filter paper hy a phenolO0 ' lb ' 20 ' 30 ' 40 ' 20 ' $0 ' '710 ' do ' 9'0 ' ,bo ' I l b ' ,io 1 1 MICROGRAMS OF SUGAR s-ater solvent (,E?), but the!- cannot then be determined by the anthrone reagent because Figure 1, Standard curves residual phenol, held tenaciouslJ- in the paper, 1. D-Xylose, Coleman Jr., 480 mp, 17 mg.of phenol interferes TT-ith the green...