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  • Spectrophotometric total reducing sugars assay based on cupric reduction.

Spectrophotometric total reducing sugars assay based on cupric reduction.

Talanta (2015-11-26)
Kevser Sözgen Başkan, Esma Tütem, Esin Akyüz, Seda Özen, Reşat Apak
ABSTRACT

As the concentration of reducing sugars (RS) is controlled by European legislation for certain specific food and beverages, a simple and sensitive spectrophotometric method for the determination of RS in various food products is proposed. The method is based on the reduction of Cu(II) to Cu(I) with reducing sugars in alkaline medium in the presence of 2,9-dimethyl-1,10-phenanthroline (neocuproine: Nc), followed by the formation of a colored Cu(I)-Nc charge-transfer complex. All simple sugars tested had the linear regression equations with almost equal slope values. The proposed method was successfully applied to fresh apple juice, commercial fruit juices, milk, honey and onion juice. Interference effect of phenolic compounds in plant samples was eliminated by a solid phase extraction (SPE) clean-up process. The method was proven to have higher sensitivity and precision than the widely used dinitrosalicylic acid (DNS) colorimetric method.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Phenol, puriss., meets analytical specification of Ph. Eur., BP, USP, 99.5-100.5% (GC)
Sigma-Aldrich
Phenol solution, Equilibrated with 10 mM Tris HCl, pH 8.0, 1 mM EDTA, BioReagent, for molecular biology
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Liquified Phenol, ≥89.0%
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Phenol, ≥96.0% (calc. on dry substance, T)
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Sodium hydroxide-16O solution, 20 wt. % in H216O, 99.9 atom % 16O
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Supelco
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Supelco
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Copper(II) chloride dihydrate, powder, BioReagent, suitable for cell culture
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3,5-Dinitrosalicylic acid, used in colorimetric determination of reducing sugars
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Gallic acid monohydrate, ≥99% (HPLC)
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Sigma-Aldrich
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