Thin-layer chromatography TLC plates

PLC is used for separations of 2 to 5 mg of sample on thin-layer chromatography (TLC) plates (0.25-nun layer thickness) or high-performance TLC (HPTLC) plates (0.1-mm thickness). In these instances, the method is termed micropreparative TLC. The isolation of one to five compounds in amounts ranging from 5 to 1000 mg is carried out on thicker layers. PLC is performed for isolation of compounds to be used in other tasks, i.e., further identification by various analytical methods, such as ultraviolet (UV) solution spectrometry [1] or gas chromatography/mass spectrometry (GC/MS) [2], obtaining analytical standards, or investigations of chemical or biological properties [3]. 

Merck 60 F254 silica gel thin-layer chromatography (TLC) plates... 

TLC. Aliquots of samples and standards were run on silica-coated thin layer chromatography (TLC) plates in either n-butanol/acetic acid/water (4 1 1 by vol. (BUOH/HAC/H2O)) or n-propanol/concentrated ammo-nia/water (8 1 11, pre-equilibration). These eluents were previously described (Keller et ah, 1984) for the two-dimensional TLC-separation of elastin cross-links. 

Spots from thin-layer chromatography (TLC) plates may often be used directly in the mass spectrometer without eluting thus for air-sensitive compounds, when TLC is done in a glove box, a concentric tube may be directly loaded with the unknown plus support the concentric tube is recommended because it minimizes loss of silica gel into the ion source. 

The method is flexible since thin layer chromatography (TLC) plates can be simply treated with a variety of chemicals thus imparting a wide range of properties to the stationary phase. 

After removal of solvent in vacuo, the yellow residue is chromatographed on silica thin layer chromatography (TLC) plates using hexane-CH2Cl2(85 15) as eluent. The major product, 2, is a nearly colorless band observed at Rf = 0.17. This band can be seen better by using an UV lamp and UV sensitized TLC plates (precoated TLC plates, silica gel 60 F-254, layer thickness 0.25 mm, Merck). This band is separated from the starting material (Rf = 0.47) and several minor bands and the products are eluted from the silica gel with CH2C12. An analytically pure sample can be obtained by recrystallization from hexane at - 20 °C. Yield 0.053-0.070 g (30-40%). 

In the case of enzymes involved in biochemical pathways, the isolation is often based on activity assays. The nature of the activity assay depends on the enzymatic reaction and can involve, for example, the detection of a product on a thin-layer chromatography (TLC) plate (see Chapter 4, Section 1.2.1), the appearance or disappearance of a specific absorbance in a spectrophotometric assay, or a coupled assay involving the oxidation or reduction of a co-factor such as nicotinamide dinucleotide (NAD(H)), which can be measured by changes in fluorescence. 

Optional Equipment for Sample Analysis 1. Silica gel G thin layer chromatography (TLC) plates 2. TLC tanks 3. Crystalline iodine (H) for staining... 

Taylor and co-workers further demonstrated the value of open-access LC/MS systems for generating a widened scope of pharmaceutical analysis applications, including (1) characterization of synthetic intermediates and target compounds (2) reaction monitoring (3) reaction optimization (4) analysis of preparative HPLC fractions and (5) analysis of thin layer chromatography (TLC) plate spots. The availability of these methods led to the increased use of LC/MS for structural analysis. The short analysis time and reliable structure confirmation resulted in the use of LC/MS as a first choice for structure characterization for synthetic chemistry applications, as well as an expanded, and perhaps, integrated role of sample generator and analyst. 

When formed on cellulose [thin-layer-chromatography (TLC) plates], the colored forms of 6-nitro-8-methoxyBIPS and of trimethylindolinospironaphthoxa-zine are stabilized against thermal or photoerasure by interaction with nickel or zinc salts of hydroxy carboxylic acids or dicarboxylic acids. The zinc salts of 1-hydroxy-... 

Activate a silica-gel thin-layer chromatography (TLC) plate by heating for 5 min in a 100°C oven. This procedure drives off excess moisture from the plate so that the TLC separation is more reproducible. 

It is impossible to conclude this discussion on FAB without mentioning the possibility of recording the spectrum of a substance directly from a thin-layer chromatography (TLC) plate (84AC109 84UP1), as this will have direct applications (on paper chromatography) in carbohydrate analysis. 

On silica gel thin-layer chromatography (TLC) plates eluted with a mixture of cyclohexane-ethanol (97 3, by volume), vitamin Aj alcohol and re/ro-vita-min Ai alcohol (Rp values 0.10 and 0.09, respectively) are separated from the pair vitamin Aj acetate/re/ro-vi-tamin Aj acetate (Rp values 0.48 and 0.45, respectively) and vitamin Aj palmitate (Rp value 0.78) and anhy-drovitamin Aj (Rp value 0.87) [5]. Geometric isomers of retinol are separated on silica gel plates using... 

In order to achieve the optimum accuracy, precision, and sensitivity, most quantitative analyses are performed by using high-performance thin-layer chromatography (TLC) plates and direct quantification by means of a modern optical densitometic scanner with... 

After anaerobic incubation of reaction mixture at 37°C for 24h, the alkane containing fraction was prepared by chloroform extraction. Chloroform extracts were separated on silica gel 60 thin layer chromatography (TLC) plate with hexane as a developing solvent. Radioactivity was measured by liquid scintillation counter (LS6500, Beckman). 

A concentrated DCM solution of photolytically degraded PBO was spotted onto a silica thin-layer chromatography (TLC) plate and chromatographed using 20% ethyl acetate in DCM. The most intense coloured band (red/pink close to the origin) was scraped from the plate and eluted from the silica with methanol. 

The thin layer chromatography (TLC) plates that we buy are slide glasses coated with silica gel. In order to visualize UV-active organic compounds, the silica gel is coated with a layer of fluorescent dye Flur. Therefore, UV-active compounds can be detected under UV light. Occasionally, non-UV-active compounds are also seen. One case is iodides, which are UV-light quenchers, while another case is inorganic salts, often seen on the baseline the salts are visualized under UV simply because they cover the fluorescent dye "Flur."... 

The fluorescence and phosphorescence of quinazoline, 6-chloro-4-phenyl-and 6-chloro-l-methyl-4-phenylquinazolin-2(lH)-one were recorded in ethanol containing 1% of concentrated sulfuric acid. The luminescence of these compounds on thin-layer chromatography (TLC) plates saturated with ethanol was reported. 4-Morpholino- and 4-piperidino-6-methoxy-2-phenyl-quinazoline also have luminescent properties, and the ultraviolet fluorescence in the crystals and in hexane or benzene solution was discussed. The time and wavelength resolved emission from quinazoline vapor at low pressures was studied with a pulsed frequency double-dye laser and were compared with those of quinoxaline and cinnoline. ... 

The [3H]inositol-labeled phospholipids are separated from other phospholipids on thin-layer chromatography (TLC) plates. After elution, the radioactive inositol phospholipids are cochromatographed with standards and visualized by exposure to iodine vapors, or by spraying with 10% CUSO4 in 8% H3PO4, then scanned for radioactivity (Gamier et al., 1994 Baron et al., 1989). 

The rate of migration of a component band through a column or thin layer chromatography (TLC) plate depends on the distribution of molecules between the mobile phase and stationary phase. The factors which influence the distribution and hence retention are... 

Raman and IR spectroscopy may be used to analyse spots on thin layer chromatography (TLC) plates. Unlike other methods, such as mass spectrometry or NMR, the spectrum may be obtained in situ without the need of scraping the spot from the plate and extracting the substance from the sihca matrix. Dispersive Raman miaos-copy has been used to collect spectra from active dmg substance on a plate [18,88]. 

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