Furfural, determination

Pentoses have frequently been determined in soils by the furfural-phloro-glucinol method.But phloroglucinol also gives precipitates with a variety of other aldehydes, such as 5-methyl-2-furaldehyde, 5-(hydroxymethyl)-2-furaldehyde, and formaldehyde. Orcinol and aniline acetate are much more specific reagents, and no aldehyde present in the hydrochloric acid distillate from soils has been found to interfere in the furfural determination by the orcinol method. The orcinol and aniline acetate methods give, for various Swiss and Norwegian soils, a pentose anhydride content of 0.5 to 8.5 % of the soil organic matter (see Table III) no corrections were made for the furfural derived from uronic acids. 

Hexoses yield hydroxymethylfurfural, and methyloses yield methylfurfural. These substances are not produced in quantitative yields, and they interfere with the furfural determination. (See Chapters I and VI.)... 

Type C requires the most complex data analysis. To illustrate, we have reduced the data of Henty (1964) for the system furfural-benzene-cyclohexane-2,2,4-trimethylpentane. VLB data were used in conjunction with one ternary tie line for each ternary to determine optimum binary parameters for each of the two type-I ternaries cyclohexane-furfural-benzene and 2,2,4-... 

Furfural was first isolated in the eady nineteenth century. Dobereiner is credited with the discovery. He obtained a small amount of a yellow "oil" (too Htde to characterize) as a by-product in the preparation of formic acid (8). Other chemists found that the same "oil" having a charactedstic aroma could be obtained by boiling finely divided vegetable materials such as oats, com, sawdust, bran, etc, with aqueous sulfuric acid or other acids (9,10). The oil was present in the Hquid resulting from condensation of the vapors produced during heating. The empirical formula was determined by Stenhouse... 

Jaganathan, J. and Dugar, S.M., Authentication of straight whiskey by determination of the ratio of furfural to 5-hydroxymethyl-2-furaldehyde, JAOC Int., 82, 997, 1999. Wang, R. and Schroeder, S.R., The effect of caramel coloring on the multiple degradation pathways of aspartame, J. Food Sci. 65, 1100, 2000. 

Lage, M.A., Simal, J., Yanez, T., Analytical methods applied to coffee liqueur. III. Determination of furfural, caffeine and tannic substances, Tecnicas de Laboratorio, 12,204,1989... 

Explosion temperatures were determined for a wide range of combustible liquid and solid organic materials sealed into glass tubes with potassium perchlorate. The lowest temperatures were shown by mixtures with ethylene glycol (240°), cotton Enters (245°) and furfural (270°C). 

Hydrolysis products of neomycin may be an amino-sugar, a pentose or furfural depending on the reaction conditions chosen. Each of these entities has been utilised for indirect spectrophotometric determination of neomycin. 

Vigorous hydrolysis of neomycin results in the formation of furfural which may be quantitated in a number of different ways- 5 156. Dutcher et all57 use(j a UV spectrophotometric procedure, measuring the absorbance of the solution at 280nm. A similar procedure combined with measurement of the optical rotation has been used by Brooks et all58 to determine the neomycin B and C content... 

Determination of xylan is frequently made by estimation of furfural production. Data so obtained, even when appropriately corrected for furfural that arises from uronic acid, may be high if araban is present in the polysaccharide preparation. In the absence of interfering carbohydrates, furfural estimation may lead to accurate xylan values. 

Furfural even in dilute aqueous solution gives, almost at once, a precipitate of the phenylhydrazone with phenylhydrazine acetate. Collect the precipitate at the pump and dry. Purify by dissolution in a little ether and careful addition of petrol ether until crystallisation begins. Melting point 97°-98°. Method for quantitative determination of furfural. 

Hydrocarbon distillates in the gas oil range ( diesel or derv ) are subject to duty when used as a road fuel. Gas oil, which is often identical to diesel oil in hydrocarbon composition, is exempt from duty when used for stationary machines. In order to prevent its misuse as a road fuel, gas oil is marked with a mixture of 1,4-dfhydroxyanthraquinone (quinizarin), 2-fiirfuraldehyde (furfural) and a red dye. An automatic method for the extraction, identification and determination of quinizarin in gas oil has been used hy the Laboratory of the Government Chemist (LGC) for some years. The presence of furfiiral provides evidence for legal prosecution and the numbers of analyses ordered in the UK merit automatic analysis. 

The lARC has determined that there is limited evidence in animals and inadequate evidence in humans for the carcinogenicity of furfural. Overall, furfural is not classifiable as to its carcinogenicity to humans. 

Guthrie and co-workers11" have measured tile liquid heal capacity of funm from - KJX to 2r C . The room lempeta-lure value have been determined for dioxanc" urn) furfural," The method of Yuan and Slid has been used to extend the useful range ol the data/ ... 

The room temperature viscosities ol dioxtmc and furfurut have been measured Cwxlant for the equation proposed by Van Vcl/en. Cordozo. and I-angcnk.imp are available for furan. Till, and dioxanc - The const.inis for furfural were determined from experimental daru ... 

Pentosans. This determination is made by Tollens and Kriiger s method, which is based on the transformation of pentosans into furfural by distillation with hydrochloric acid and on subsequent precipitation of the furfural with phloroglucinoL The analysis comprises, therefore, two distinct operations ... 

Detection and Determination of Furfural.—(A) Qualitative Test 10 c c of the spirits are shaken with 10 drops of aniline and 1 c.c. of concentrated acetic acid and then allowed to stand in presence of furfural, a red coloration forms either immediately or after some time. 

For this purpose a standard solution containing 0-005 gram of furfural per litre of pure 50% alcohol is prepared, the spint to be tested being also brought to 50% concentration. 10 c c of each of the two liquids are treated at the same time with 10 drops of aniline and 1 c c of concentrated acetic acid. If, after 20 minutes, the colorations are approximately similar, they are compared in the Duboscq colorimeter, if, however, the two colorations differ greatly, the test is repeated m the manner described for the determination of the aldehydes (tee above). The proportion of furfuraldehyde present is readily calculated from the colorimeter readmgs... 

A number of workers have investigated the oxidation of dextrins80 and starch81 with halogens in neutral and alkaline solutions and have reported the presence of significant amounts of anhydroglucuronic acid units in the products obtained, as determined by furfural formation. No attempt has been made, however, to develop a practical synthesis of D-glucuronic acid by this means. 

The KIE in the dehydration of fructose to 5-(hydroxymethyl) furfural has been determined624 and interpreted as arising in the rate-determining addition of H+ to... 

---