Prepared by
Nam Sun Wang
Department of Chemical & Biomolecular Engineering
University of Maryland
College Park, MD 20742-2111

Table of Contents


Unlike other carbohydrates, sucrose is the only non-reducing common disaccharide. Consequently, most tests for sugar detection utilizing such reagents as Benedict's solution, Fehling's solution, and DNS (3,5-dinitrosalicylic acid) solution result in negative readings for sucrose. (The student should convince himself of this fact by performing the test with a pure sucrose solution.) However, these methods can still be applied if sucrose is first hydrolyzed in an acid solution to yield glucose and fructose. This method is a straightforward modification of the original DNS method for glucose analysis.

List of Reagents and Instruments

A. Equipment

B. Reagents


  1. Add 1 drop, or 20 µl, of concentrate HCl solution to 1 ml of the sucrose solution. Allow the hydrolysis to proceed at 90ºC for 5 minutes.
  2. Add 3 drops, or 0.05 ml, of the 5 N KOH solution to neutralize the acid, because the DNS method must be applied in an alkaline condition to develop the red brown color which represents the presence of reducing sugars.
  3. Add the DNS reagent and follow the DNS method henceforth.
  4. Generate a calibration curve to correlate the absorbance to the sucrose concentration.


The DNS method can be applied twice to measure the individual concentrations of a mixture of glucose and sucrose. First, a small part of the original sample is consumed in measuring the glucose concentration by following the original DNS procedure. Another part of the sample is hydrolyzed and subsequently subjected to the same DNS procedure. The difference in the absorbance between the acid treated sample and the untreated sample is due to the presence of sucrose. The sucrose concentration can then be calculated from a calibration curve based on that difference in the absorbance.

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Sucrose Assay by the Dinitrosalicylic Colorimetric Method
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Nam Sun Wang
Department of Chemical & Biomolecular Engineering
University of Maryland
College Park, MD 20742-2111
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e-mail: nsw@umd.edu