Colorimetric determination of the molar substitution of 2-hydroxybutyl and related starch ethers

The molar substitution (MS) of 2-hydroxyalkyl starch ethers, e.g. 2-hydroxybutyl starch, can be determined spectrophotometrically. The principle involves a dehydrative-hydrolytic generation of n-butyraldehyde from the 2-hydroxybutyl starch ether substituent in concentrated sulfuric acid. The resulta...

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Bibliographic Details
Published in:Carbohydrate polymers 1992, Vol.17 (4), p.313-318
Main Authors: Harry-O'Kuru, R.E., Moser, K.B., Gordon, S.H.
Format: Article
Language:English
Subjects:
Applied sciences
calorimetry
chemical reactions
corn starch
derivatives
ethers
Exact sciences and technology
hydroxylation
Natural polymers
Physicochemistry of polymers
spectral analysis
Starch and polysaccharides
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Summary:The molar substitution (MS) of 2-hydroxyalkyl starch ethers, e.g. 2-hydroxybutyl starch, can be determined spectrophotometrically. The principle involves a dehydrative-hydrolytic generation of n-butyraldehyde from the 2-hydroxybutyl starch ether substituent in concentrated sulfuric acid. The resultant hydrolyzate containing the aldehyde and allylic species of the substituent is complexed with 2,2-dihydroxyindan-1,3-dione (ninhydrin) in bisulfite giving a colored complex the absorbance intensity of which can be determined by a spectrophotometer at 470 nm. From the maximum intensity observed the concentration of butyraldehyde in the sample is derived by interpolation on a standard curve. The percentage of 2-hydroxybutane in the sample is calculated by comparison of the concentration of substituent to that of the hydrolyzed starting material. The MS is then calculated from the per cent substituent.
ISSN:0144-8617
1879-1344
DOI:10.1016/0144-8617(92)90175-P