The purpose of the presence of phenol in the determination of sugars by phenol-sulfuric acid method?

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Luay A. Al-Helaly

The PRINCIPLE of using phenol in this assay is: In hot acidic medium glucose is dehydrated to hydroxymethyl furfural. This forms a green coloured product with phenol and has absorption maximum at 490 nm. The color for this reaction is stable for several hours, and the accuracy of the method is within ±2% under proper conditions...

Best wishes

Dhia Ahmed Taain

Thank you very much Prof.Dr. Luay A. Al-Helaly

Zohreh Khayat

In presence of H2SO4, sugars oxidize to furfural or hydroxymethyl furfural. These products then react with phenol to form a conjugated system with a yellow-gold color. In presence of naphthol, a purple color is produced (Molisch's Test). You can find more in: Chapter Phenol-Sulfuric Acid Method for Total Carbohydrates

Thank you very much Prof.Dr. Zohreh Khayat

Pushpendra Koli

In certain cases, different plant tissues develop yellow color after adding sulfuric acid then why there is a need to add Phenol?