Elution ethylacetate

Bromocriptine 2 (0.65 g, 1 mmol) was dissolved in 100 ml of dry ethanol and 60 ml of tetrafluoroboric acid / diethylether complex (85 %) was added while stirring. After standing overnight at RT the solvent was evaporated and the raw product isolated by extraction in the system dichloromethane 12% ammonia in water and evaporated to the dry residue. This residue was applied to the chromatographic column (I.D. = 2 cm, lenght = 20 cm) packed with silicagel and eluted with dichloromethane / ethylacetate =1 1. The fractions containing 2 were evaporated to the dry residue and crystallized from alcohol. 

Dried and powdered aerial parts of the plant (500 g) were extracted with actone at room temperature for 24 h. After filtration, the extract was evaporated in vacuo to a small volume. The extract was concentrated by distillation and evaporated to dryness. The residue (16 g) was chromatographed over a silica gel column eluting with on petroleum ether, a gradient of petroleum ether-chloroform, up to chloroform, followed by chloroform-ethylacetate, up to ethylacetate and fiially with methanol. 

HAAs HPLC-MS. Supelco LC-CN or Supelco LC-18-DB column. Mobile phase NH4 (acetate) (pH = 6.8)-ACN-MeOH in gradient elution. Low ppb level Cooked beef products, beef extract, fried beef MeOH extraction, cleaning on XAD-2, ethylacetate elution. 1%... 

Aldehyde (5 mmol), ethane 1,2-diol (5 mmol) and metal sulfate (5 mmol) supported on silica gel (1.65 g) were mixed in a Pyrex test tube and subjected to microwave irradiation for 36 min. After complete conversion, as indicated by TLC, the reaction mass was charged directly on small silica gel column (100-200 mesh) and eluted with ethylacetate-hexane (2 8) to afford pure acetal in 80-98% yield. 

Wilfordil Hook F (celastraceae) on the basis of bioassay-directed fractionation. The ethanol extract was concentrated in an ethylacetate layer of an ethylacetate-water participation. The ethylacetate extract was eluted on silica gel with chloroform and 5% methanol in chloroform. The latter fraction was further chromatographed on silica AR-CC-7 with chloroform to yield a triptolide-enriched fraction. This was further chromatographed on silica AR CC-7 to yield triptolide (137) which on crystallization from CH2Cl2-Et20 was obtained as white needles, m.p. 

Meprobamate has been separated from the hydroxy-and keto meprobamate (see Figure , Compound I and II) on an alumina column using stepwise gradient elution. The eluants used were benzene, ethylacetate, acetone and methanol, both alone and in mixtures33. 

Elute column with ethylacetate, methanol, and ammonium hydroxide (80 18 2% v/v). 

The column extraction is based on the following principle the water sample is distributed as a film at the contact with the adsorbent. Afterwards, the elution with immiscible water solvents is performed (e.g. diethylether, ethylacetate or chlorinated solvents). All the lyphophyle pollutants are extracted from the aqueous into the organic phase. During the process the aqueous phase remains on the stationary phase and emulsion formation is no longer possible. The extract can be vaporized and the pollutants will be analyzed. 

General procedure for addition of diethyzinc to benzaldehyde The polymer (2-15 mol %) is stirred in dry toluene to swell the polymer under nitrogen atmosphere for 90 minutes. Benzaldehyde (1.0 equivalent) is added, stirred for 20 minutes, cooled to O C, and diethyl zinc (2-4 equivalents) is added. The reaction mixture is allowed to warm to room tenqierature gradually over a period of 1 hr and stirred at RT for 48-72 hrs. This was followed by quenching the reaction mixture with 2.0 N hydrochloric acid solution. The polymer was removed by filtration, and the aqueous layer extracted with diethylether. The cmde product was purified over a column of silica gel, eluting with light petrol ethylacetate (99 1 to 98 2). The purity of the piue product was recorded over GC, and the specific rotation recorded on a polarimeter. The enantiomeric excess is calculated with reference to the literature values. 

Another way of detection of ammonia has been reported by Kataoka et al., in which ammonia was converted into its benzenesulfonyl dimethylaminomethylene derivative by a convenient procedure involving benzenesulfonylation with benzenesulfonyl chloride and subsequent reaction with dimethyl formamide dimethyl acetal, and was determined by GC with FPD using a DB-I capillary column (Figures 9.16 and 9.17). The derivative was very stable on standing in ethylacetate, eluted as a single peak, and provided an excellent response in the FPD. Ammonia in environmental water samples could be measured without interference from coexisting substances. 

Elution of the sorbent is carried out using organic solvents such as ethylacetate, methanol, acetonitrile, or mixtures of solvents. Frequently, the eluent is concentrated to achieve higher sensitivity and the final extract is analysed without any additional treatment. Nevertheless, when analysing heavily contaminated samples, some authors have included a extract cleanup step using activated alumina. ° The recoveries obtained were satisfactory in several applications, as can be seen in Table 28.6. 

Purification of 12,13,17-THOA and DEOA. The crude lipid extract ( 2 g) was suspended in 30 mL of n-hexane and applied on a column (25 cm i.d. x 35 cm height) packed with silica gel 60 (70-230 mesh, EM Science). After the column was washed with 800 mL of n-hexane/ethylacetate (9 1), DEOA was eluted with n-hexane/ethylacetate (8 2). The column was further washed with n-hexane/ethylacetate (2 8), and then eluted with ethylacetate to recover THOA [ 75% purity by gas chromatography (GC)]. When necessary, the DEOA and THOA fractions were further purified by preparative TLC using toluene/1,4-dioxane (95 5) and toluene/1,4-dioxane (7 3), respectively. 

In contrast to reversed-phase, the stationary phase in normal-phase chromatography is polar, usually silica or alumina, and uses nonpolar solvents, e.g., hexane and ethylacetate, that are not compatible with the API processes nsed in LC-MS. In normal-phase chromatography compounds elute progressively from the least to the most polar. The technique is not applicable to the highly polar compounds encountered... 

A widely employed chromatographic system is the one based on polyamide plates eluted with water-formic acid (200 3 v/v) in the first direction and benzene-acetic acid (9 1 v/v) in the second direction. A third run with 1 M ammonia-ethanol (1 1 v/v) or ethylacetate-acetic acid-methanol (20 1 1 v/v/v) in the direction of solvent 2 resolves especially basic Dns-amino acids or Glu/Asp and Thr/Ser pairs. 

Thin-layer chromatography (TLC) is mainly applied in micropreparative taxoid separation.Silica gel 6OF254 preparative plates are usually employed for this purpose. The problem of taxoid separation involves not only their similar chemical structure (e.g., paclitaxel vs. cephalomannine) but also the different coextracted compounds usually encountered in crude yew extracts (polar compounds such as phenolics and non-polar ones such as chlorophylls and biflavones) the separation is therefore very difficult. The common band of paclitaxel and cephalomannine was satisfactorily resolved from the extraneous fraction in isocratic elution with ethylacetate as polar modifier " and n-heptane-dichloromethane as solvent mixture, and was of suitable purity for high-performance liquid chromatography (HPLC) quantitative determination. The combination of micropreparative... 

Systematic studies on selection of the best mobile phases to ensure the best micropreparative separation of analyzed taxoids—especially of 10-DAB 111 as well as its less polar derivatives, baccatin III, paclitaxel, and cephalomannine, obtained from the extracts of fresh and dried needles and stems of T. baccata— have been undertaken by Mroczek and Glowniak.The TLC investigation on silica gel included solvent systems with one and two polar modifiers and multicomponent mobile phases, as well as some multiple development techniques and gradient elutions. As polar modifiers, methanol, acetone, dioxane, ethylacetate and ethylmethylketone as well as their mixtures were reinvestigated dichloromethane, chloroform, benzene, toluene, heptane, and their mixtures were used as solvents. 

Fractionation according to functionality. PPG eluted in pure ethylacetate in adsorption mode. 

The elution solvents used were benzene-ethylacetate-acetone (100 5 2) for antioxidants and chloroform-hexane (2 1) for UV absorbers and butanol-glacial acetic acid (97 3) for organotin compounds. An ethanolic solution of 2,6-dichloro-p-benzoquinone-4-chlorimine was used as spray reagent for antioxidants and UV stabilisers. 

Benzyloxycarbonylamino) 2-nitrophenol (3.39) in 1 M sodium hydroxide (17 ml) and acetone (30 ml) at 5° is treated with tetra-O-acetyl-a-D-mannopyranosyl chloride (3.7 g) dissolved in acetone (20 ml). After 12 hr at 5°, the mixture is poured into water (200 ml) and extracted five times with chloroform. XJnreacted phenol is recovered from the chloroform extracts by six extractions with IM sodium hydroxide. The chloroform layer is washed with dilute acid, dried, and evaporated to give a mixture of (V) and mannopyranosyl chloride. Elution of the mixture from neutral alumina (Woelm) with chloroform gives the unreacted mannosyl chloride. Compound (V), seen as a pale yellow band on the column, is eluted with chloroform-ethylacetate (1 1). Yield, 0.7 g (11%) m.p., 188° (from n-propanol) - -68° (C = 0.2, CHCI3). 

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