Chloroform/toluene/acetone separation

Another HPTLC method has been developed for the separation of kaempferol and quercetin in the extract of Ginkgo biloba leaves showing beneficial effect in brain diseases. Leaves were refluxed with methanol for 30 min then filtered. The filtrate was refluxed with 25 per cent HC1 for 60 min then neutralized with ammonia and the clear supernatant was applied for HPTLC. Silica plates were predeveloped in chloroform-methanol (1 1, v/v). Separation was performed with toluene-acetone-methanol-formic acid (46 8 5 1, v/v) as the mobile phase using incremental multiple development. A densitogram illustrating the good separation charactersitics of the system is shown in Fig. 2.42. The relative standard deviation (RSD) of the method was low (1.37 and 1.40 for kaempferol and quercetin,... 

Column chromatography is generally used for compositional analyses (ASTM D-2007 ASTM D-2549). The former method (ASTM D-2007) advocates the use of adsorption on clay and clay-silica gel followed by elution of the clay with pentane to separate saturates, elution of clay with acetone-toluene to separate polar compounds, and elution of the silica gel fraction with toluene to separate aromatic compounds. The latter method (ASTM D-2549) uses adsorption on a bauxite-silica gel column. Saturates are eluted with pentane aromatics are eluted with ether, chloroform, and ethanol. 

Example 3.3 Separation Alternatives of the Mixture Acetone/Chloroform/Toluene [5]... 

There are many well-established methods for separation and structure determination of ecdysteroids.20 27 A newly described method is two-dimensional thin-layer chromatography. It has been used to separate complex mixtures of phytoecdysteroids. Silica plates were developed first with toluene—acetone—ethanol—25% aqueous ammonia (100 140 32 9 v/v) and then developed in the other direction with chloroform—methanol—benzene (25 5 3 v/v)48... 

The mobile phase for a particular separation is usually selected empirically using prior personal experience and literature reports of similar separations as a guide or by use of a systematic mobile-phase optimization scheme, usually the PRISMA model. Typical mobile phases that have been used for separations of many classes of pesticides on sihca gel have been mixtures of hexane-acetone, toluene-acetone, chloroform-diethyl ether, and toluene-methanol, whereas mobile phases for RPTLC analyses on Cig layers are usually methanol-water and acetonitrile-water mixtures. 

Roy et al. (1991) extracted the pigments of green leafy vegetables in methanol-acetone-diethyl ether (1 1 1) the extracts were evaporated, reconstituted in the same solvent, and separated by TLC on silica gel G plates with a chloroform-petroleum ether-toluene-acetone (5 4 4 3) mobile phase. Pheophorbide b, mixed carotenoid, pheophorbide a, chlorophyll b, pheophytin b, chlorophyll a, pheophytin a, and carotene bands were obtained. This method can be used to detect artificial and natural colorants in food products. 

Keep halogenated and nonhalogenated solvents separately (e.g., mixing chloroform and acetone can cause unexpected reactions in the presence of bases). Halogenated solvents are organic solvents such as chloroform, dichloromethane, trichlorotriflu-oroethane, and dichloroethane. Some nonhalogenated solvents are pentane, heptane, ethanol, methanol, benzene, toluene, AT,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and acetonitrile. 

The following chiral reagents were employed for diastereomer formation before sample application and chromatography on silica gel or silica gel G TLC plates (L)-leucine Af-carboxyanhydride for D,L-dopa-carboxyl- " C separated with ethyl acetate/formic acid/water (60 5 35) mobile phase and detected by ninhydrin [7 f 0.38 (d)/0.56 (l)] [43] Af-trifluoroacetyl-L-prolyl chloride for D,L-amphetamine separated with chloroform/methanol (197 3) and detected by sulfuric acid/formaldehyde (10 1) (Rf 0.49 (d)/0.55 (l)) [44] Af-benzyloxycarbonyl-L-prolyl chloride for D,L-methamphetamine separated with n-hexane/ethyl acetate/acetonitrile/diisopropyl ether (2 2 2 1) and detected by sulfuric acid/formaldehyde (10 1) [/ f 0.57 (l)/0.61 (d)] [44] (l/ ,2/ )-(-)-l-(4-nitrophenyl)-2-amino-1,3-propanediol (levobase) and its enantiomer dextrobase for chiral carboxylic acids separated with chloroform/ethanol/acetic acid (9 1 0.5) and detected under UV (254 nm) light R[ values 0.63 and 0.53 for 5- and / -naproxen, respectively) [45] (5)-(4-)-a-methoxyphenylacetic acid for R,S-ethyl-4-(dimethylamino)-3-hydroxybutanoate (carnitine precursor) with diethyl ether mobile phase [/ f 0.55 R)/0J9 (5)] [46] and (5)-(4-)-benoxaprofen chloride with toluene/acetone (100 10, ammonia atmosphere) mobile phase and fluorescence visualization (Zeiss KM 3 densitometer 313 nm excitation, 365 nm emission) (respective R values of R- and 5-isomers of metoprolol, oxprenolol, and propranolol were 0.24/0.28, 0.32/0.38, and 0.32/0.39) [47]. 

A suspension of 4 g of trans-2-(2,5-dimethoxy-4-methylphenyl)-cyclopropanecarboxylic acid in an equal volume of H20, was treated with sufficient acetone to effect complete solution. This was cooled to 0 °C and there was added, first, 2.0 g triethylamine in 35 mL acetone, followed by the slow addition of 2.5 g ethyl chloroformate in 10 mL acetone. This was stirred for 0.5 h, and then there was added a solution of 1.7 g NaN i in 6 mL If20, dropwise. After 1 h stirring at 0 °C, the mixture was quenched by pouring into H20 at 0 °C. The separated oil was extracted with EtzO, and extracts dried with anhydrous MgS04. Removal of the solvent under vacuum gave a residue of the azide, which was dissolved in 10 mL anhydrous toluene. This solution was heated on the steam bath until the nitrogen evolution was complete, and the removal of the solvent under vacuum gave a residue of crude isocyanate as an amber oil. This intermediate isocyanate was... 

The toluene phase was separated and discarded. The aqueous phase, together with a precipitated water- and toluene-insoluble oil, was made alkaline and extracted repeatedly with chloroform. The chloroform solution was concentrated in vacuo. The residue was recrystallized from a mixture of acetone and ether (alternatively, from chloroform and ether), and formed needles melting at 164° to 165°C. It was identified as 3-benziloyloxy-l-azabicyclo[2.2.2]octane. 

Figure 15 Phase separation conditions of the gas-liquid microflows. Solvents 1,1-decanol 2,1-octanol 3,1-propanol 4, nitrobenzene 5, dodecane 6,1,4-dioxane 7, ethanol 8, water 9, carbon tetrachloride 10, m-xylene 11, hexane 12, toluene 13, chloroform 14, ethyl acetate 15, dichloromethane 16, hexane 17, acetone 18, pentane and 19, diethyl ether. The open circles show the theoretical higher limit, the open triangles the theoretical lower limit, the solid circles the experimental results of the higher limit, and the solid triangles the experimental results of the lower limit (Aota et al., 2009a).

The concentration profiles are displayed in Figure 3.15 (right-hand). The first column has 50 theoretical trays with feed on 20, entrainer/feed ratio 2 and reflux ratio 3.5. A bound in the concentration profile takes place around the feed. In the stripping zone the toluene carries out preferentially the chloroform. The rectification part separates mainly the binary acetone-chloroform, the entrainer concentration being negligible. The profile of the second column... 

Figure 3.15 Separation of acetone and chloroform with toluene (alternative 1).

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