A critical examination of the Nelson-Somogyi method for the determination of reducing sugars

In a critical examination of the modified Nelson-Somogyi method for reducing sugars proposed by Somogyi in 1952, the following were established:

• 1.1. The blue complex absorbs maximally at 750 mμ, but full color development at this wavelength is only achieved after 1.5 hr.
• 2.2. For maximum reduction of the copper reagent by fructose, glucose, and arabinose heating periods of 5, 20, and 25 min, respectively, are required, and data are presented which indicate that each worker ascertain the required time of heating under his experimental conditions.
• 3.3. A constant ratio of copper reagent to sugar solution must be used and the volume of arsenomolybdate reagent should not be less than half the volume of the copper reagent.
• 4.4. The difficulties experienced in working at wavelengths longer than 500 mμ can be attributed to changes in the absorption spectrum of the colored complex obtained when increasing amounts of sugar are determined, but these difficulties can be eliminated by increasing the volume of arsenomolybdate reagent used.