Chemical tests for identification of rutin are based on the properties of phenolic hydroxyl groups of rutinose and of the benzene nucleus. It may be chromatographically identified on a paper chromatogram developed descendingly (25% isopropyl alcohol) as a brown–orange band. Rutin is even conveniently identified by UV, Nuclear Magnetic Resonance (NMR), Infrared (IR) and mass spectroscopy.

1. An aqueous solution of rutin when treated with a solution of ferric chloride gives a dark green colour.
2. An orange–yellow precipitate intensified in colour by alkalies is formed when an aqueous solution of rutin is treated with lead acetate.
3. Similar coloured precipitates are formed by aqueous solutions of rutin with ammonium molybdate and antimony trichloride.

A. Method I

1. To 20 kg of freshly harvested buckwheat leaves taken in a stainless steel steam-heated vessel, add sufficient quantity of 85% isopropyl alcohol (IPA-75 l) to cover the plant material.
2. The solution is brought to boil as rapidly as possible and held at boiling temperature for 10 min.
3. The hot extract is drawn off by pressure through heavy filter sheets. After the second and third similar extractions (each with 45 l of IPA) followed by filtration, the combined extracts are concentrated by evaporation to one-fourth their original volume.
4. The boiling concentrate is then carefully strained through heavy filter sheets, washed with boiling water (2 l) and the filtrate and washings are immediately cooled by the addition of crushed ice (6 l) to bring the temperature to 5°C.
5. The cold solution containing crude crystallized rutin is allowed to stand for 1 h and filtered carefully, after thoroughly washing with small portions of cold water. The obtained rutin is dried to constant weight at 110°.

B. Method II

1. To 10 kg leaf meal contained in a stainless steel vessel, add 200 l of boiling water. The leaf and water mixture is boiled for about 15 min and filtered hot.
2. The spent leaf meal is washed with further 10 l hot water and the filtrate and the washings are collected in open wooden or stainless steel tanks. It is allowed to stand for about 24 h at room temperature.
3. Rutin crystallizes in yellow crystals as the temperature of the solution falls down. The crystals are filtered out and the filter cake washed with cold water.
4. Purified rutin so obtained may be recrystallized from ethanol.