Determination of Levulose in Presence of Dextrose and Sucrose

Quantifying carbohydrate fractions in forage plants

“…Selective determination of fructose in the presence of glucose generally depends on a choice of alkalizing agents and temperature of the reaction bath during oxidation. Jackson and Matthews (1950) used carbonate and bicarbonate, whereas Becker and Englis (1941) employed a mixture of sodium carbonate and sodium phosphate buffer for selective oxidation, and determined the reduction product titrimetrically with sodium thiosulfate or ceric sulfate (Englis and Becker, 1939).…”

Sugar Analysis by Alkaline Ferricyanide Method - Determination of Ferrocyanide by Iodometric and Other Procedures

“…Notes. Since metastannic acid is a colloidal precipitate, contamination is increased if the solution is evaporated to dryness, as some authors recommend (1). The process of evaporating to dryness consumes an excessive amount of time, and if the evaporation is hastened by overheating, cupric nitrate may be decomposed, with consequent contamination of the metastannic acid.…”

“…The last-mentioned was carried out according to Kolthoff (4•) by making the solution 3 N with hydrochloric acid, adding a 1 N potassium iodide solution, and titrating the iodine with thiosulfate after the mixture had stood for about 5 minutes in a glassstoppered flask. The conditions for the sugar oxidation were those previously described for the selective oxidation of levulose (1). Since under these conditions dextrose is only slightly oxidized and the products of oxidation left might be expected to respond somewhat differently from those after oxidation of levulose, experiments were carried out with each of the sugars.…”

Ceric Salts in Volumetric Analysis

“…Many have used a cerate solution in the determination of reducing sugars. The sugar was treated with an excess of Fehling's solution (14,126) or of ferricyanide in alkaline medium (9,31,56,57,143,144,148), and the cuprous oxide or ferrocyanide formed has been estimated by the usual procedures employing ceric salts.…”