Visualization thin layer chromatography

Chemical stabiUty studies are monitored by siUca gel thin-layer chromatography (dc) or by high performance Hquid chromatography (hplc) using a reverse-phase C g coated column (24). Hplc peaks or dc spots are visualized by thek uv absorption at 245 nm the tic spots can also be detected by ceric sulfate or phosphomolybdic acid staining. 

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). 

Fractions may be monitored by thin-layer chromatography on silica gel, developing with 10% v/v ethyl acetate in hexane and visualizing with iodine vapor. The following Rf values were observed famesol, 0.07 farnesyl acetate, 0.35 bromohydrin acetate, 0.20. 

Analysis by thin layer chromatography (TLC) indicates product formation and a small amount of starting material. TLC was performed on Merck Silica gel 60 F-254 coated on aluminum sheets. Product 3 has Rf = 0.44 (elution with 70 30 petroleum ether-ethyl acetate visualization with iodine vapor). 

Analytical thin-layer chromatography was performed on E. Merck silica gel 60 F254 plates (0.25 mm) and compounds were visualized by dipping the plates in a cerium sulfate-ammonium molybdate solution followed by heating. 

Besides the calculation of the different sulfonated species, it is also possible to determine them directly by chromatographic methods. Separation of the ester sulfonate and the disodium salt is achieved by thin-layer chromatography on silica gel plates. With a solvent mixture of acetone and tetrahydrofuran (90 10 v/v) the disodium salt stays at the start whereas the ester sulfonate has an R value of 0.2. With the more polar solvent 0.1 N H2S04 + methanol + chloroform the ester sulfonate and the disalt have Rf values of 0.36 and 0.14. For visualization, the plate is sprayed with pinacryptol yellow. In UV light (254 and... 

Visualization Techniques for Thin-Layer Chromatography.892 Qualitative Identification and Nicroreaction Techniques it ... 

Dichloromethane extraction of culture broth, thin layer chromatography of the extract, and visualization with 5% vanillin/sulfuric acid spray is effective for detecting cycloheximide in culture broth. Cycloheximide applied to TLC plates in amounts as low as 1 yg/spot will produce visible color with the vanillin spray. 

Caffeine was extracted from ficw varieties of roasted coffee beans and was determined in parallel by (1) measurement of spot area after thin layer chromatography on silica gel GF plates (development with chloroform/ cyclohexane/glacial acetic acid, 8 2 1, visualization in UV light), and (2) Kjeldahl N determination. Caffeine contents by (1) and (2), respectively, in the five varieties analyzed were (percent in DM) Santos lave 0, 1.10, and 1.12 Java Robusta 3, 1.19, and 1.22 Camerun Robusta 2, 1.16, and 1.19 Mocca 2, 1.21, and 1.26 Guatemala 0, 1.18, and 1.20. (1) is considered slightly less accurate than (2) but rather easier and more rapid.21... 

Analytical thin layer chromatography (TLC) was conducted on 10 x 2.5-cm precoated glass plates (silica gel GF, 0.25-mm thickness, Analtech), eluted with 10% ethyl acetate in hexane, and visualized with both UV (254 nm) and aqueous 50% sulfuric add spray/heating. The carbene complex moves as an orange spot on TLC the reaction is complete when this spot is no longer visible. 

Fig. 3. Diagrams of electrochemical cells used in flow systems for thin film deposition by EC-ALE. A) First small thin layer flow cell (modeled after electrochemical liquid chromatography detectors). A gasket defined the area where the deposition was performed, and solutions were pumped in and out though the top plate. Reproduced by permission from ref. [ 110]. B) H-cell design where the samples were suspended in the solutions, and solutions were filled and drained from below. Reproduced by permission from ref. [111]. C) Larger thin layer flow cell. This is very similar to that shown in 3A, except that the deposition area is larger and laminar flow is easier to develop because of the solution inlet and outlet designs. In addition, the opposite wall of the cell is a piece of ITO, used as the auxiliary electrode. It is transparent so the deposit can be monitored visually, and it provides an excellent current distribution. The reference electrode is incorporated right in the cell, as well. Adapted from ref. [113],...

The identification of bromocriptine mesilate in the dosage form can be carried out by thin layer chromatography using Merck plates with dichloromethane/methanol/formic acid 78 20 2 (v/v/v) and subsequent uv-visualization at 254 and 360 nm. Using this method, it is important to only air-dry the spot after application to the plate, since more vigorous evaporation of the solvent will give rise to artifacts (32). 

Most of the reactions described in the following chapters were monitored by Thin Layer Chromatography (TLC) using plastic TLC plates coated with a thin layer of Merck 60 F254 silica gel. The products were detected by using an ultraviolet lamp or the TLC plates were treated with p-anisaldehyde reagent, prepared as explained below, and then heated to 120 °C to stain the spots. After visualization and measurement, the Rf values were recorded. 

Injection volumes of 5pl were used for both sample solutions and comparison standards. Qualitative residue confirmation was accomplished with thin layer chromatography using silica gel. Plates were developed with 1% chloroform in n-heptane, and visualized with alkaline silver nitrate spray as the chromogenic agent. Alternatively, p,p5-DDT and p,p5-TDE were confirmed by treatment with 5% methanoic potassium hydroxide [40]. Partial confirmation of Dieldrin was achieved by fractionating the analysis solution on a Mills column, thus isolating Dieldrin in the second fraction [35],... 

Thin layer chromatography was carried out on 20x20cm glass plates coated 0.25mm thick with a suitable support and dried overnight. Silica gel G, silica gel H and cellulose were examined as the solid phases for chromatography of methanearsonate, arsenite and arsenate. Several sprays for the visualization of the arsenicals on plates were tested. Three of the more successful reagents and the colour produced with final product are shown in Table 13.2. 

Thin layer chromatography is performed on Merck Kieselgel silica gel 60 F-254 plates eluting with 30% acetone/hexanes, visualized by a 254-nm UV lamp and... 

Aromatic amines that have been used include o-toluidine, p-aminosali-cylic acid, p-aminobenzoic acid, diphenylamine and p-aminophenol. Their ability to react preferentially with a particular carbohydrate or class of carbohydrate is often useful, e.g. p-aminophenol, which shows some specificity for ketoses compared with aldoses and is useful for measuring fructose. These reagents have proved particularly useful for the visualization and identification of carbohydrates after separation of mixtures by paper or thin-layer chromatography, when colour variations and the presence or absence of a reaction aid the interpretation of the chromatogram. 

ACS reagent grade hexanes and ethyl acetate were obtained from Aldrich Chemical Company, Inc. Thin layer chromatography was performed on Silica Gel 60 F-254 precoated plates. Chromatograms were visualized with phosphomolybdic acid reagent from Aldrich Chemical Company, Inc. 

Occasionally use several drops to spot, develop, and visualize a thin layer chromatography plate. Although thin layer is very similar to column, you should read up on it as 1 do not have time to go into the complete operation. 

Thin Layer Chromatography Procedures. Silica gel G (Suppelco, Redi-coat, 5 X 20 cm X 0.25 mm) plates were activated by heating in an oven for 1 hour at 110°C. Toxic products were spotted onto duplicate plates at concentrations corresponding to their previously determined LD99 levels. The plates were developed to 14 cm with chloroform, methanol and (6N) ammonium hydroxide (90 9.5 0.5) or chloroform, methanol, and water (60 35 8). Plates were developed and visualized by spraying with 50% aqueous sulfuric acid and charring. Undeveloped plates were scraped, the silica gel fines removed and the extracts concentrated to a residue under a nitrogen gas stream. 

Thin Layer Chromatography. TLC analysis of the WSAP was accomplished By application to silica gel G plates at a concentration of 0.1 mg and development to 14 cm with chloroform-methanol-water (60 35 8). Prior to sulfuric acid-char treatment, five components were visibly resolved. Following such treatment a total of 10 components were visualized. Duplicate plates were divided into six zones, which were scraped, eluted with methanol and assayed at a concentration of 0.2 mg equivalents... 

The progress of the reaction is monitored by thin layer chromatography, eluting with ethyl acetate (product Rf = 0.06, visualized and developed using UV light and KMn04 respectively). 

Thin layer chromatography was performed using silica plates and eluting with hexane. Potassium permanganate was used to visualize the spots. The R, values for products I and 3 were 0.38 and 0.37, respectively. 

E. Merck cellulose thin-layer chromatography plates (available from American Scientific Products) are developed with chromatography buffer (Note 13) and visualized with sulfosalicylic acid/ferric chloride spray. The system consists of a solution of 1.0 g of sulfosal icyl ic acid (from Aldrich... 

Sevgi and Guneri used thin-layer chromatography to study the stability of isoxsuprine HCl in aqueous media and in marketed ampoules [8]. The solutions and ampoules were heated at 40, 60, and 80°C, with the TLC spots being visualized under UV light at 250 nm. Quantitation was performed using the fluorescence observed at 272 nm. The authors found that under these conditions, the compound was stable in aqueous solutions for 323 days and in ampoules for 389 days. 

---