I want to prepare NaOMe (I have sodium metal and methanol), Alcl3,alcl3/hcl, naoac, naoac/h3bo3. Please i need information on the concentrations and the quantity to apply during UV Scan. Thanks.
Reagents for Ultra–Violet Spectroscopic Analysis of Flavonoids (Mabry, et al., 1970).
1. Sodium methoxide (NaOMe).
Freshly cut metallic sodium (2.5 gm.) was dissolved in 100 ml. spectroscopic methanol.
2. Aluminum chloride.
Anhydrous AlCl3 (5 gm.) was cautiously dissolved in 100 ml. spectroscopic methanol and filtration was carried out after about 24 hours.
3. Hydrochloric acid.
Fifty ml. concentrated HC1 was mixed with 100 ml. distilled water.
4. Sodium acetate (NaOAc).
Anhydrous reagent grade NaOAc was melted and allowed to stand for about 10 minutes. The material was then powdered and stored in a dry bottle.
5. Boric acid (H3BO3).
Anhydrous powdered reagent grade H3BO3 was used.
Reagents for Ultra–Violet Spectroscopic Analysis of Flavonoids (Mabry, et al., 1970).
1. Sodium methoxide (NaOMe).
Freshly cut metallic sodium (2.5 gm.) was dissolved in 100 ml. spectroscopic methanol.
2. Aluminum chloride.
Anhydrous AlCl3 (5 gm.) was cautiously dissolved in 100 ml. spectroscopic methanol and filtration was carried out after about 24 hours.
3. Hydrochloric acid.
Fifty ml. concentrated HC1 was mixed with 100 ml. distilled water.
4. Sodium acetate (NaOAc).
Anhydrous reagent grade NaOAc was melted and allowed to stand for about 10 minutes. The material was then powdered and stored in a dry bottle.
5. Boric acid (H3BO3).
Anhydrous powdered reagent grade H3BO3 was used.
In recording the UV spectrum of flavonoidal compounds, the certain reagents find use in finding the presence of phenolic hydroxyls at various positions of the flavonoidal ring as well as the presence of chelated hydroxyl group.
It is usual to add these reagents to a solution of the sample for which UV spectrum is recorded.
The commonly used shift reagents are:
1. Sodium Acetate solid
2.Sodium methoxide or sodium ethoxide solution (dissolve few tiny pieces of freshly cut sodium in 10ml of methanol or ethanol. This will serve for 5 samples)
3. Boric acid solid solid
4. Aluminium Chloride solid
The steps followed are:
1. Record UV spectrum of the flavonoidal compound or flavonoid fraction of a plant extract in ethanol
2. To the sample in ethanol 5ml add a few drops of freshly prepared sodium methoxide solution. Shake the cuvette thoroughly. Then record the UV spectrum.(bathochromic shift in UV max compared to the original spectrum will be observed if hydroxyl groups are present in the flavonoidal sample)
2. To the sample in ethanol 5ml add a pinch of sodium acetate solid. Shake the cuvette thoroughly and allow to settle. Then record the UV spectrum.(bathochromic shift in UV max compared to the original spectrum will be observed if a hydroxyl group at the 7 position is present in the flavonoidal sample)
3.To the sample in ethanol 5ml add a pinch of boric acid solid. Shake the cuvette thoroughly and allow to settle. Then record the UV spectrum.(bathochromic shift in UV max compared to the original spectrum will be observed if a ortho dihydroxy system is present in the flavonoidal sample). Add few drops of Conc,HCl to the same sample solution and record the UV spectrum again. The UV max will return to the original value. This confirms presence of ortho dihydroxy system.
4.To the sample in ethanol 5ml add a pinch of Aluminium chloride solid . Shake the cuvette thoroughly and allow to settle. Then record the UV spectrum.(bathochromic shift in UV max compared to the original spectrum will be observed if chelated hydroxy group is present in the flavonoidal sample). Add few drops of Conc,HCl to the same sample solution and record the UV spectrum again. The UV max will return to the original value. This confirms presence of chelated hydroxy group.
- Badges
- Science method
- Similar topics
- Methodology
- Absorption Spectroscopy
- UV-Visible Spectroscopy