Eluent silicas

SPE procedure T5 e of sorbent Sample volume Eluent Silica Cl 8 (cartridge Sep-Pak ) 2.5-10 mL (sample extract) MeOH 40-70% (v/v)... 

An important publication by Kost et al. (63JGU525) on thin-layer chromatography (TLC) of pyrazoles contains a large collection of Rf values for 1 1 mixtures of petroleum ether-chloroform or benzene-chloroform as eluents and alumina as stationary phase. 1,3- and 1,5-disubstituted pyrazoles can be separated and identified by TLC (Rf l,3>i y 1,5). For another publication by the same authors on the chromatographic separation of the aminopyrazoles, see (63JGU2519). A-Unsubstituted pyrazoles move with difficulty and it is necessary to add acetone or methanol to the eluent mixture. Other convenient conditions for AH pyrazoles utilize silica gel and ethyl acetate saturated with water (a pentacyanoamine ferroate ammonium disodium salt solution can be used to visualize the pyrazoles). 

Dihydro-2(3H)-turanthlone (3).2 Butyrolaclone 1 (0 86 g. 10 mmoO and [2,4-bis(4-methoxyphenyl)-l, 3-dilhia 2,4-diphospheiane-2,4-disui(ide) 2 (2 02 g, 5 mmol) in PhMe (10 mL) were heated to reflux until no more starling malenal was detected (TLC or GC) After cooling, the solvent was stripped off and the mixture was punlied on silica gel using CH2CI2 as eluent to afford 3, mp 96-97 C... 

Anthrarufin [l,5-dihydroxy-9,10-anthraquinone] [117-12-4] M 240.1, m 280 (dec), pKj 9.90, pK 11.05. Purified by column chromatography on silica gel with CHCl3/Et20 as eluent, followed by recrystn from acetone. Alternatively recrystd from glacial acetic acid [Flom and Barbara J Phys Chem 89 4489 1985]. 

Bismethylaminoanthraquinone (Disperse Blue 14) [2475-44-7] M 266.3, A,max 640 (594)nm. Purified by thin-layer chromatography on silica gel plates, using toluene/acetone (3.1) as eluent. The main band was scraped off and extracted with MeOH. The solvent was evapd and the dye was dried in a drying pistol [Land, McAlpine, Sinclair and Truscott J Chem Soc, Faraday Trans I 72 2091 7976]. 

Distyrylpyrazine [14990-02-4] M 284.3, m 219 . Recrystd from xylene chromatographed on basic silica gel (60-80 mesh) using CH2CI2 as eluent, then vac sublimed on to a cold surface at 10 torr [Ebied J Chem Soc, Faraday Trans / 78 3213 1982], Operations should be carried out in the dark. 

Methylanthracene [613-12-7] M 192.3, m 204-206° Chromatographed on silica gel with cyclohexane as eluent and recrystd from EtOH [Werst 7 i4m Chem Soc 109 32 1987]. 

Resin-based TSK-GEL PW columns are durable to alkaline conditions, which cannot be used with silica-based columns. Such durability facilitates separations with basic eluents and allows the use of alkaline cleaning reagents. 

PSS columns for fluorinated eluents PSS PFG columns were developed by PSS because users worldwide were unsatisfied with the stability of conventional organic SEC columns when running solvents such as hexafluroisopropa-nol (HFIP). Because polymeric gels tend to be unstable in fluorinated media, PSS modified silica to achieve better stability while maintaining perfect chromatographic performance. 

Let us consider the separation of polymethylmethacrylate (PMMA) on a nonmodified silica column as an example. In THE (medium polar eluent) the PMMA eludes in size exclusion mode because the dipoles of the methylmethacrylate (MMA) are masked by the dipoles of the THE. Using the nonpolar toluene as the eluent on the same column, the separation is governed by adsorption because the dipoles of the carbonyl group in the PMMA will interact with the dipoles on the surface of the stationary phase. The separation of PMMA in the critical mode of adsorption can be achieved by selecting an appropriate THF/toluene mixture as the eluent. In this case all PMMA samples... 

The elution behavior of various polymers near their critical adsorption point with silica gel packings and various eluents has been studied (12). It was of interest to apply hybrid column systems composed of active ( critical ) packings (silica gels) in combination with nonactive (nonadsorptive) PS/DVB and DVB-based gels. Some PS/DVB and DVB gels exhibited rather strong... 

To a solution of nitroolefin 4 (200 mg) and isocyanide 16 (169 mg) in a 1 1 mixture of THF and isopropanol (5 mL) was added the guanidine base A -t-BuTMG (180 mg). The resulting solution was heated to 50°C for 3 h, poured into water, and extracted with dichloromethane. The organic layer was dried over sodium sulfate and filtered through a short column of silica gel (eluent dichloromethane). Evaporation under vacuum of the solvent gave the desired pyrrole as a pale crystalline solid (272 mg, 90%) mp... 

Figure 12.7 Cliromatograms of a polycarbonate sample (a) microcolumn SEC ti ace (b) capillary GC ti ace of inti oduced fractions. SEC conditions fused-silica (30 cm X 250 mm i.d.) packed with PL-GEL (50 A pore size, 5 mm particle diameter) eluent, THE at aElow rate of 2.0ml/min injection size, 200 NL UV detection at 254 nm x represents the polymer additive fraction ti ansfeired to EC system (ca. 6 p-L). GC conditions DB-1 column (15m X 0.25 mm i.d., 0.25 pm film thickness) deactivated fused-silica uncoated inlet (5 m X 0.32 mm i.d.) temperature program, 100 °C for 8 min, rising to 350 °C at a rate of 12°C/min flame ionization detection. Peak identification is as follows 1, 2,4-rert-butylphenol 2, nonylphenol isomers 3, di(4-tert-butylphenyl) carbonate 4, Tinuvin 329 5, solvent impurity 6, Ii gaphos 168 (oxidized). Reprinted with permission from Ref. (14).

Figure 12.8 Mia ocolumn size exclusion chromatogram of a styrene-aaylonitrile copolymer sample fractions ti ansfeired to the pyrolysis system are indicated 1-6. Conditions fused-silica column (50 cm X 250 p.m i.d.) packed with Zorbax PSM-1000 (7p.m 4f) eluent, THF flow rate, 2.0 p.L/min detector, Jasco Uvidec V at 220 nm injection size, 20 nL. Reprinted from Analytical Chemistry, 61, H. J. Cortes et al, Multidimensional chromatography using on-line microcolumn liquid chromatography and pyrolysis gas chromatography for polymer characterization , pp. 961 -965, copyright 1989, with peimission from the American Chemical Society.

The enantioselective determination of 2,2, 3,3, 4,6 -hexachlorobiphenyl in milk was performed by Glausch et al. (21). These authors used an achiral column for an initial separation, followed by separation of the eluent fraction on a chiral column. Fat was separated from the milk by centrifugation, mixed with sodium sulfate, washed with petroleum ether and filtered. The solvent was evaporated and the sample was purified by gel permeation chromatography (GPC) and silica gel adsorption chromatography. Achiral GC was performed on DB-5 and OV-1701 columns, while the chiral GC was performed on immobilized Chirasil-Dex. 

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