benedict's test
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Benedict’s TestScreening Tests for Certain
Inborn Errors of Metabolism
Benedict’s TestO Test for presence of reducing
sugars:
O Reducing monosaccharides:O glucose, fructose, glyceraldehyde and
galactose
O DisaccharidesO Lactose and maltose
Benedict’s TestO Benedict’s reagent can be used to
test for presence of glucose in urineO Indication of diabetes
O Heating a Benedict’s solution mixed with monosaccharides will produce a reddish-orange color
Benedict’s Reagent
Contains blue copper(II) sulfate (CuSO4)
reduced to copper(I) ions
(Cu+)
which are precipitated as red copper oxide which is
insoluble in water.
Benedict’s ReagentO Carbohydrates that contain aldehydes or a-
hydroxymethyl ketones can be oxidized by Cu(II)ions are classified as reducing sugars. They reduce the Cu(II) to Cu(I).
O
H + Cu2+
O
H + Cu2O(s)
R R
Results
Negative Blue
Green to Yellow +
Yellow to Brown ++
Brown to Orange +++
Orange to Red ++++
Reducing Substance
Clinical State
Drugs Ascorbic acid, chloral hydrate, tetracyclines, sulfonamides, chloramphenicol
Fructose Fructosemia, essential fructosuria, hereditary fructose intolerance
Galactose Galactosemia, classic and variant (galactokinase deficiency)
Glucose Diabetes mellitus, renal glycosuria, Fanconi’s Syndrome, Wilson’s Disease
Homogentisic acid Alkaptonuria
Lactose Lactase deficiency, lactose intolerance, newborn
Phenolic compound Phenylketonurias, tyrosinosis
Xylose Excessive fruit intake
Xylulose Pentosuria
Urinary Substances and Clinical Syndromes Associated with Reducing Substances
Methodology
Pour 5 ml of
Benedict’s Reagent
Heat to Boiling
Add 8 Drops of
Urine
Boil for 2 minutes/ Place in boiling
bath for 3 minutes
Results
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