Silica column chromatography

TBAF (1 mmol, 1 M in THF) was added to the combined organic extracts and the resulting solution was stirred for 3 h. The solution was then washed once with water and once with brine, back-extracted with diethyl ether, and the organic layer was dried over anhydrous MgS04. The solvent was then removed in vacuo and the product was purified by silica column chromatography. In order to determine the ee, the product was converted into the corresponding (R,R)-2,3-dimethylethylene ketal and then analyzed by GC analysis (Chiraldex G-TA) for the diastereomeric ketals. 

Mix sample with concentrated NH4OH/MeOH, extract with CH2Cl2/isooctane, 2 + 1. Silica-column chromatography. 

PrOH/hexane (3 2), centrifuge. Evaporate three times from 10 vol of CHCl3/MeOH, 2 1. Silica-column chromatography. Add menaquinone-7 as internal standard to purified fraction. 

The synthesis and purification of polystyrene methacryloyl macromonomers (PS-MA) in the molecular weight range Mn= 1000-2000 g mol 1 by living anionic polymerization of styrene (S), termination with ethylene oxide (EO), and subsequent reaction with methacrylic chloride has already been described in detail elsewhere [180] (see also Scheme 16). In this context it has to be emphasized that the hydroxyethyl-terminated PS-MA macromonomer precursor (PS-OH) as obtained after purification of the crude PS-OH by silica column chromatography (cyclohexane/dichloromethane 1/1 v/v) and as charged in the PS-MA synthesis still contains up to about 15 wt-% of non-functionalized polystyrene (PS-H). This PS-H impurity of the PS-MA macromonomer does not interfere with the PS-MA synthesis and the subsequent TBA/PS-MA copolymerization and is easily and conveniently removed from the resulting PTBA-g-PS graft copolymer (see below). 

The composition of the PAA-g-PS graft copolymer reaction product and its purification, especially as far as the removal of unreacted PS-MA macromonomer by silica column chromatography is concerned, and the successful selective cleavage of the ferf-butyl ester under acidic conditions to render the graft copolyelectrolyte PAA-g-PS were analyzed by XH NMR spectroscopy and SEC. Figure 8a shows the SEC curves of the polystyrene macromonomer (PS-MA), the crude poly (ferf-butyl acrylate-gra/f-styrene) (PTBA-g-PS) and the PTBA-g-PS the polymethylacrylate (PMA) originates from esterification of the poly (acrylic acid) (PAA) obtained after complete saponification of the graft copolymer and represents the backbone. The XH NMR spectra of PSMA, PTBA-g-PS and of the final reaction product PAA-g-PS are shown in Fig. 8b. 

Silica gel (240-360 pm) and size exclusion media, Sepharose CL4B (40-165 pm) and Sephadex G25m (Sigma-Aldrich) are used for silica column chromatography and size exclusion chromatography respectively (see Note 2). 

The removal of dioxin from water by modified alum flocculation was monitored by the disappearance of a 0.08 uCi spike of 3-H labeled dioxin (obtained from A. Poland, repurified by silica column chromatography) in jar type experiments. A conventional uncharged Garratt-Callahan polymer //7882 was used for floe modification. The labeled dioxin spike, dissolved in hexane-methylene chloride, 80 20, was introduced into 200 ml of water in several ways. The spike was added directly to the water, it was added to water containing the... 

Oiticica oil triglycerides have been separated by silica column chromatography into four fractions a monoketo fraction (27.3%), dike to fraction (32.1%), a more polar triglyceride fraction (12.9%) and others (15.9%). The level of licanic acid was reported to be lower than that previously reported, i.e. 46% instead of 70-80% (Evans 1967). 

Alternariol can be determined using gradient RPLC with UV detection at 254 nm, although fluorescence or MS detection have also been used. Sample preparation involves extraction with dichlor-methane and purification of the extract by silica column chromatography using diethyl ether-hexane in the washing step and ethyl acetate-methanol for elution of analyte. Besides, cleanup of the sample can be carried out in two steps using first a polypropylene Cl8 SPE column, followed by aminopropyl SPE column. 

For the synthesis of cis-9,trans- - % 2 and af-9,cA-l 1-18 2 the triple bond of methyl santalbate and its Z-isomer was reduced with zinc, which was activated with Cu(Ac)2 and AgNO, to form the Z-double bond (12). Any unreacted enyne was removed by treatment with mercury(II)sulfate in methanol, which converted the enyne to the corresponding keto-ene. Subsequently the latter was separated by silica column chromatography. 

Applications of countercurrent distribution to lipid purification were already reported in the 1950s. These included the isolation of PC, SPM, or cerebrosides from brain tissue, or the placenta. It was then mentioned that lipids easily emulsify, and this adversely affects the ability to separate them. Therefore these methods were only used for crude separation. The method also requires a long time for phase separation before each phase transfer, and this procedure needs to be repeated 500-3000 times. Otsuka and Yamakawa reported the application of droplet CCC to the purification of phospholipids and glycohpids. Because the stationary phase retention is much more stable in TC-CCC than with HS-CCC, it has become possible to select appropriate two-phase solvent systems. In this study, we showed the successful separation of human brain lipids by using TC-CCC. Additionally, if an isolated band can be observed on HPTLC, the lipid can be purified by using silica column chromatography after TC-CCC cmde separation. 

Solvent Solubility Solvent solubility has been used in the work at Imperial College London because the method can yield a recovery of 100% of the initial sample. Fractionation using silica (column chromatography or TLC) has been shown to lead to loss of the high-mass material on the silica [57] and detected... 

Further purification was accomplished by silica column chromatography (see Note 10). The silica must first be saturated with ammonium hexafluorophosphate before the sample is eluted with dichloromethane/acetonitrile/methanol (see Note 8). 

Tributyltin hydride-mediated hydrodebromination of bromoarenes is selectively carried out. However, removal of the tin residue should be carefully carried out. The 10% w/w anhydrous potassium carbonate-silica repeatedly reduces organotin impurity levels below 15 ppm in this system (Table 3-12). In addition, organotin reagents such as tributyltin hydride, allyl stannanes, vinyl stannanes, arylstannanes, and distannanes can be purified by the K2CO3 and silica column chromatography. On the contraiy, halostannanes and sulfonated stannanes are trapped through this process (Table 3-13). 

---