Seliwanoff's test

Positive Seliwanoff’s test

Seliwanoff’s test is a chemical test which distinguishes between aldose and ketose sugars. Ketoses are distinguished from aldoses via their ketone/aldehyde functionality. If the sugar contains a ketone group, it is a ketose and if it contains an aldehyde group, it is an aldose. This test is based on the fact that, when heated, ketoses are more rapidly dehydrated than aldoses.

Seliwanoff-Reaction

The reagents consist of resorcinol and concentrated hydrochloric acid:

• The acid hydrolysis of polysaccharides and oligosaccharides yields simpler sugars.

• The dehydrated ketose then reacts with the resorcinol to produce a deep cherry red color. Aldoses may react slightly to produce a faint pink color.

Fructose and sucrose are two common sugars which give a positive test. Sucrose gives a positive test as it is a disaccharide consisting of fructose and glucose.

References

• Seliwanoff, Theodor (1887). "Notiz über eine Fruchtzuckerreaction". Berichte der deutschen chemischen Gesellschaft 20: 181. doi:10.1002/cber.18870200144. 
• Katoch, Rajan (2011-06-30). Analytical Techniques in Biochemistry and Molecular Biology. p. 71. ISBN 9781441997845. http://books.google.de/books?id=rCU2-gvkjo0C&pg=PA71. 
• Chawla (2003-01-01). Practical Clinical Biochemistry: Methods and Interpretations. p. 35. ISBN 9788180611087. http://books.google.de/books?id=gP2whA97gPgC&pg=PA35.